Naval History and Heritage Command

Report of the Allied Conference on Minelaying in the Mediterranean Sea

SECRET.                                         Copy No. 49

No. 02063.

REPORT OF THE

ALLIED CONFERENCE ON MEDITERRANEAN MINELAYING

HELD AT

MALTA,

ON 6th, 7th, 8th and 9th AUGUST, 1918.

15th August, 1918.

CONTENTS.

Page.

I.     Agenda ...  ...  ...  ...  ...  ...  ...  ...  ...

II.    Members present, officers and officials attending ...

III.   Recommendations ...   ...  ...  ...  ...  ...  ...  1

IV.    Opening remarks by the President ... ... ...  ...  4

V.     Report of proceedings and recommendations ...  ...  4

VI.    Appendix 1.-Extracts from a paper on deep minefields and mine barrages compiled by Captain Litchfield-Speer  20

VII.   Appendix 2.-List of Delegates comprising the

       Sub-Committees ...    ...  .... ...  ...  ...  ...  24

VIII.  Appendix 3.-Report by Sub-Committee on the question of the Dardanelles Minefields ...  ...  ...  ...  ...  25

IX.    Appendix 4.-Report by Sub-Committee on mining and anti-submarine barrages in the Ægean Sea  ...  ...  ...  26

X.     Appendix 5.-Report by Sub-Committee on mining and anti-submarine barrages in the Straits of Otranto and between Cape Bon and Sicily  ...  ...  ...  ...  ...  ...  29

ALLIED CONFERENCE ON MEDITERRANEAN MINELAYING.

_______

AGENDA

_______

1.  Minefields off the Dardanelles against surface vessels.

(a)  Present situation.

(b)  Arrangements already made for extending and reinforcing minefield.

(c)  Further proposals as regards extensions and reinforcements.

2.  Anti-submarine minefields and barrages in the Mediterranean.

To lay down general principles as to the suitability of:-

  (a)  Deep minefields,

  (b)  Mine net barrages,

  for the principle areas in which it is desired to take anti-submarine measures.

3.  Anti-submarine minefields and barrages in the Mediterranean.

  (a)  Minefields and barrages in the Straits of Otranto and the Adriatic.

  (b)  Minefields and barrages between Sicily and the African Coast.

  (c)  Minefields and barrages in the Ægean.

  (d)  Minefields and barrages in the Straits of Gibraltar.

The general principles on which they should be established or extended and the priority in which they should be undertaken.

4.  What other areas are suggested additional to those already named in (3), and what should be their order of priority?

5.  What is the approximate extent of supply of personnel and material for the foregoing measures?

6.  To nominate sub-committees to consider in detail the schemes which it is decided to study and to issue the necessary instructions to them.

7.  On receipt of the sub-committees’ reports they will be considered by the Conference who will then further consider the allocation of the supply and responsibility for execution among the Allied nations.

G. C. DICKENS,1  

5th August, 1918.                                     Secretary.

SECRET.

LIST OF MEMBERS OF THE ALLIED CONFERENCE ON MEDITERRANEAN MINELAYING.2

______________________

PRESIDENT:

Great Britain.

          Vice-Admiral The Honourable SIR SOMERSET A. GOUGH-CALTHORPE.3

DELEGATES:

Japan.

          Rear Admiral K. SATO.

          Commander K. KISHII.

Italy.

          Contrammiraglio EDOARDO SALAZAR.

          Capitano di Corvetta F. RUSPOLI.

          Capitano di Corvetta R. DE BELLEGARDE DE SAINT-LARY.

          Tenente di Vascello A. LAIS.

France.

          Contre Amiral J. E. C. M. RATYE.

          Capita[i]ne de Vaisseau J. E. H. FROCHOT.

          Capitaine de Fregate E. F. M. H. MAGESCAS.

          Capitaine de Corvette P. M. J. H. DE LAURENS CASTELET

          Capitaine de Corvette E. L. H. DUBOIS.  (Secretary).

United States of America.

          Rear-Admiral J. STRAUSS.

          Commander C. R. TRAIN.

          Lieutenant N. DAVIS.4

Great Britain.

          Captain F. S. LITCHFIELD-SPEER.

          Captain R. M. BURMESTER (Commodore, 2nd Class).

          Captain E. R. MORANT.

          Commander G. C. DICKENS (Secretary).5

ATTENDING:

Commodore G. H. BAIRD

       (Director of Shipping Movements, Mediterranean).

Brigadier-General F. V. TEMPLE, R.M.

       (British Director of Intelligence, Mediterranean).

Lieutenant-Commander J. H. GODFREY, R.N.

Lieutenant-Commander E. M. GIBBINGS, R.N.

Lieutenant G. C. BANISTER, R.N.

Lieutenant de Vaisseau J. LE BIGOT.

Commissaire Auxiliare de 3eme Classe A. DE PONTAC} Assistant

Assistant-Paymaster A. P. SHAW, R.N.          } Secretaries.

Assistant-Paymaster J. S. BAILLIE, R.N.R.

                                              Stenographers

Miss CICELY KING.                                         

 

ALLIED CONFERENCE ON MEDITERRANEAN MINELAYING.

6th, 7th, 8th and 9th August, at Malta.

_______________________________

RECOMMENDATIONS.

Minute 1 of Agenda.

      Minefields off the Dardanelles Against Surface Vessels.

     (a) Present situation.

     (b) Arrangements already made for extending and reinforcing minefields.

     (c)Further proposals as regards extensions and reinforcements.

     The Conference having noted the present position of minefields off the Dardanelles and considered the Report of the Sub-Committee (vide Appendix 3) recommend that the re-establishment of the Dardanelles minefield should be proceeded with in accordance with the proposals of the Sub-Committee (vide Appendix 3), the mines being supplied by France and England. They also recommend that a minefield against surface ships and submarines should afterwards be laid between Imbros and Cape Gremea when suitable mines become available.

Minute 2 of Agenda.

Anti-Submarine Minefields and Barrages in the Mediterranean.

     To lay down general principles as to the suitability of:-

          (a) Deep Minefields,

          (b) Mine Net Barrages,

for the principle areas in which it is desired to take anti-submarine measures.

     No recommendations were placed on record by the Conference regarding these points, but a paper was read by Captain Litchfield-Speer, on Deep Minefields and Net Barrages (vide Appendix 1).

Minute 3 of Agenda.

    Anti-Submarine Minefields and Barrages in the

Mediterranean.

(a) Minefields and Barrages in the Straits of Otranto and the Adriatic.

(b) Minefields and Barrages between Sicily and the African coast.

(c) Minefields and Barrages in the Ægean.

(d) Minefields and Barrages in the Straits of Gibraltar.

     The general principles on which they should be established or extended and the priority in which they should be undertaken.

(a) 1. i. That the present mine net barrage now being laid by Italy and France be completed as designed between Otranto and Fano Island and that the United States should reinforce it by laying deep mines, to complete its efficacy as a barrage, to a depth of 85 metres from the surface.

     ii.  Where the great depth of water does not permit of mines of present types being laid, the depth of the net obstruction should be increased to at least 85 metres.

     iii. With reference to the passage of submarines over the top of the net, the Conference were not satisfied that any present form of towed explosive obstruction had proved effective in anything but fine weather and considered that further experiments must be made before deciding on this question. In the meanwhile, the present mobile barrage patrol should continue. Admiral Raty did not concur with the recommendations embodied. He was of the opinion that the space on top of the nets should be guarded by moored mines and by towed de Quillac mines.

     2.   That a mine barrage between Fano Island and a point on the Italian coast between Santa Maria di Leuca and Otranto be laid by the United States conditional upon the successful production of a mine suitable for the depth involved. That this barrier extend from 3 metres from the surface down to a total depth of 85 metres. That a gate be left near the western end not exceeding 5 miles in length and to be narrowed in future should experience warrant its reduction, such gate to be free of all mines down to a depth of 12 metres, but to be thoroughly patrolled by craft capable of fighting submarines and in sufficient numbers to compel the submarines to dive into the minefield. That inasmuch as the United States Government would undertake to furnish the mines and lay them, the operation of laying, controlling and maintaining the barrage be under their jurisdiction. Rear-Admiral Salazar agreed on the condition that when battleship have to pass through the channel it may be swept to a greater depth.

     3.   If, however, the strategical objections raised by Italy could be overcome, the Conference was of opinion that a complete mine barrier with suitable gate between Otranto and Cape Linguetta should be laid in preference to the one proposed between Santa Maria di Leuca and Fano Island. This would be done with the material already designed, as the water was shoaler, and moreover the barrier would be less exposed to the sea. Admiral Salazar did not concur in the mine barrier being placed in the latter position.

  (b.) The conference was not prepared to recommend the establishment of a mine barrage between Sicily and Cape Bon in view of the difficulty of passing the large amount of traffic through such a barrage without very large gateways, which would render the barrage ineffective.

     The representatives of the United States and Japan did not, however, concur in this opinion, and the former considered that this barrage should be established with constricted gateways.

  (c.) 1.  It was considered that it was desirable that there should be a complete anti-submarine barrage in the Ægean Sea, to comply as far as possible with the principles laid down by the Allied Naval Council.

       2.  It was considered that the mine barrage, No. 4 of the barrages in the Ægean, in Memorandum No. 168 of the United States of America, was the most suitable that could be suggested.

       3.  I was considered that there should be one gate only, in the deepest water of the Doro Channel. If subsequently, under military urgency, it was found necessary to sweep an opening for the passage of a fleet, it could be done, but such opening was not to be maintained as a gate, and was to be closed at the earliest opportunity.

     4.  The gate should not be less than 500 nor more than 1,000 yards in width, and should be free for passage of vessels on the surface only. It would require to be guarded by day and night to prevent the passage of submarines on the surface.

     5.  Two tugs and six trawlers would be required to control the traffic, to pass sailing ships through, and to reinforce escorts in the immediate vicinity of the gate in the Doro Channel.

     For the channels between Andros, Tinos, Mykoni, Nikaria, Themina, Furni and Samos, seven vessels would require to be constantly patrolling, involving a total requirement of twelve vessels.

     6.  For the mine barrier between Samos Island and Cape Kanapitza, two watching vessels would be required, i.e., a total of three.

     7.  Aircraft should be largely used for watching the gate and the channel between Samos Island and Cape Kanapitza.

     8.  It would be necessary to maintain a sufficient armed force at Samos to prevent the enemy obtaining control of both sides of this Channel.

     9.  It was considered that the responsibility of the provision, laying and maintenance of the minefield should be entirely in the hands of the United States of America and that the method of laying and details of plans should be left to the Government responsible for executing the project.

     10.  It was considered that Great Britain should furnish all the above craft, as the zone is a British one.

     11.  The patrol vessels should be under the orders of the United States Senior Officer of the Barrage.

     12.  The allocation of the responsibility for the provision of the land forces indicated as necessary for the defence of Samos should be decided by the Allied Naval Council.

     13.  It was observed that if this project was put into execution the coastal and inter-island shipping would be largely interfered with, that this was a matter which principally affected the Government of Greece, and that this question should therefore be taken up with that country at the earliest moment possible in order that their concurrence and co-operation might be obtained.

     14.  It was suggested that a passage for small craft such as caiques, would be possible in the Eastern Ægean in the Furni Boghaz, which has a width of less than 100 yards and could be closed by a net.

     15.  It was considered that the establishment of a separate base in the Ægean for this project would <not>6 be necessary but that use should be made of the main base established in connection with the other mine barrage proposals under consideration.

     16.  Barrages guarding the northern and southern entrances to the Eubœan Channels should be proceeded with but barrages in the Gulfs of Petali and Athens were not essential. Those between Cape Dukato and Cape Vlioti and between Cephalonia and Cape Glarenza should only be considered after the main Ægean barrages had been laid.

  (d.) The Conference recommended that the possibility of a barrier in the Straits of Gibraltar should be investigated.

Minute 4 of Agenda.

     The following priority as regards the establishment of mine barrages was finally decided upon:-

1. Dardanelles. This, however, does not refer to the line of mines between Imbros and Cape Gremea, which may possibly be laid later if material is available.

2. Adriatic.

3. Ægean.

4. Protection of the entrance to the Eubœa Channel.

5. Protection of the entrance to the Gulf of Patras.

     The latter should only be considered after the minefields and barrages in the Ægean have been completed.

     Inasmuch as the laying of these mines, with the exception of the Dardanelles barrier, is a matter that is to be undertaken by the United States, the Conference considered that the United States should select a suitable base, and recommend that every facility should be offered them by the nation on whose territory this base is ultimately selected.

     Practicability of the mining proposals in deep water was dependent on definite data in regard to soundings, surface and sub-surface currents, on the lines of the proposed barrages. Action in regard to this was necessary and it was strongly recommended that it should be at once undertaken by Great Britain in the Ægean and by Italy in the Adriatic.

1st Session-Morning, Tuesday 6th August.

____________________________

REPORT OF PROCEEDINGS.

     The PRESIDENT, in opening the Conference, welcomed Rear-Admiral Strauss and the other officers who had travelled to Malta to attend it, and desired to convey to them the great satisfaction felt by those stationed in the Mediterranean, at the fact that it would soon be possible, chiefly through the assistance of the United States of America, to undertake mining in these seas on a large scale--a system of warfare they had not hitherto been able to attempt.

     The Mediterranean provided several fairly narrow passages through which enemy submarines must pass, and if the difficulties due to the great depth of water which obtained in most of these passages could be surmounted, it would be possible, if it was agreed to embark on mining on a really large scale, to place a most serious check on the activities of enemy submarines.

     The President said that he desired, before proceeding further, to express his sincere congratulations to those responsible for the laying of the Franco-Italian Fixed Barrage in the Straits of Otranto. At the Conference at Rome in February, he had stated that he doubted the efficacy of a fixed barrage in such very deep waters, and also the probability of its remaining effective in the winter gales. This barrage, which was not entirely completed, had as yet only experienced summer weather, but nevertheless it had been already the direct cause of the loss of one enemy submarine, which demonstrated that the decision to proceed with it was a wise one. He was therefore anxious to acknowledge that those officers who pressed for its being tried had been absolutely right.

     The PRESIDENT then passed to Minute (1) of the Agenda.

Minute 1 of Agenda.

     Before reviewing the extent and nature of minefields against surface craft in the vicinity of the Dardanelles, it was considered desirable to call the attention of the Conference to the following considerations.

     It was not possible to deal with this question without touching on a matter which was not directly mentioned in the Agenda. It was quite evident that no certainty could ever really be placed upon the assumption that the enemy’s fleet would be destroyed on out minefields, however well the latter were placed, and therefore, for many months to come, the possibility of enemy surface craft breaking out of the Dardanelles and getting clear of these minefields would be a constant menace.

     The fact that the 100 fathom line almost touched the northern shore of the Gallipoli Peninsula made it possible for the enemy to sweep into deep water under the guns of his shore batteries, without being molested in any way by the Allied forces.

     The Southernmost Channel extended for many miles along the enemy coast, which meant that rapid sweeping would be quite possible along it.

     It was therefore important that decisions made by the conference should not give a false sense of security when they were advising as to the number of mines it was proposed to lay in the Dardanelles area. Nothing could really ensure the destruction of the enemy’s ships, should they come out, but that they should be obliged to meet a fleet able immediately to bring them to action.

Minute 1(a) of Agenda.

Present Situation of Minefields off the Dardanelles.

     Charts showing the present situation were placed on the table, and no further explanations were deemed necessary.7

Minute 1(b) of Agenda.

Further Proposals as regards Extending and Reinforcing Minefields off the Dardanelles.

     The PRESIDENT asked Admiral Ratyé if he could explain the intentions of Admiral Gauchet8 on this point.

     ADMIRAL RATYĖ replied that he was not quite certain as to the intentions of Admiral Gauchet, but he knew that the 4,000 mines decided upon were intended to be used to relay the old minefields in the Dardanelles, and that 1,500 other mines were placed in reserve at Mudros. He was of opinion that not more than 800 mines in the old minefield were left.

     The PRESIDENT said that of the 4,000 mines, 2,000 had already been laid or were actually being laid. This question was entirely outside any new proposals as regards the Dardanelles or the Ægean further south.

Minute 1(c) of Agenda.

Further Proposals as regards Extensions and Reinforcements of Minefields off the Dardanelles.

     The PRESIDENT said he proposed that this should be dealt with by a small sub-committee composed of a French and a British officer, because it affected only the French and British.

     This was agreed to.

Minute 2 of Agenda.

     The PRESIDENT said that as some of the members of the committee, including himself, had not heard the latest views of experienced officers on this question, he would ask Captain Litchfield-Speer to explain the present situation as regards the laying of deep minefields and the placing of mine net barrages.

     CAPTAIN LITCHFIELD-SPEER remarked that the governing principles of Anti-submarine barrages were correctly stated in a Memorandum prepared by the United States (No. 168) and accepted by the Allied Naval Council in London on the 23rd July, 1918. (Memorandum No. 168 laid on the table.)

     Captain Litchfield-Speer then read some extracts from a paper on deep minefields and mine barrages. (See Appendix 1.)

Minute 3 of Agenda.

     The PRESIDENT then went on to Minute No. 3 of the Agenda, and said that what we eventually had to decide was the priority to be given to the proposed minefields or barrages, but he thought that the Conference would arrive at that better if they took the various barrages in the order laid down in the Agenda and discuss them generally on broad lines.

     He therefore proposed that the Adriatic should be taken first.

Minute 3 (a) of Agenda.

     The PRESIDENT asked Admiral Salazar if he would give his opinion generally on the question of mines and barrages in the Adriatic.

     REAR-ADMIRAL SALAZAR was of opinion that the Otranto-Fano net barrage should be completed, and that the second net barrage, as had been discussed at the Conferences at Rome and London, should be established between Otranto and Aspri-Ruga. These two barrages should be established and completed as soon as possible. The Otranto-Aspri-Ruga Barrage should go to a depth of 100 metres.

     At present in the Straits of Otranto there existed the mobile barrage and the fixed barrage, which supplemented one another. The fixed barrage was constituted as follows:

     The minefield on the parallel of Cape Otranto consisted of two lines of mines at a depth of 20 metres from the surface. This minefield extended about 8 miles from the coast, leaving a free passage of one mile close to the shore. The net barrage extended from 2 miles from the S.E. extremity of this minefield and stretched in an east-south-easterly direction towards Fano Island. On 1st August, the barrage had reached a point 15 miles from Fano, 20 miles having so far been completed.

     The completion of the net barrage depended only on the provision of the necessary material.

     The normal daily work consisted in laying about 2,000 metres, and more had been laid under exceptionally good conditions.

     The net extended from 10 metres to 55 metres below the surface. Naturally, submarines could pass over the net, especially at night.

     It was therefore proposed to complete it by towing de Quillac mines over it.

     Two lines of British Service mines off Cape Santa Maria di Leuca, extending for a distance of about five miles from the shore, leaving a passage of one mile near the coast, were being laid at a depth of 20 metres from the surface.

     It was now proposed to lay a second net barrage to supplement the first, from the N.W. extremity of the first net barrage to Aspri-Ruga on the Albanian Coast. The United States had kindly said that they would do what they could to provide the necessary material for this barrage.

     There would appear to be no difficulty in laying this barrage to the depth of 100 metres so as to prevent submarines passing under it, as all the wires, buoys, etc. would be of the same pattern now being used for the Otranto-Fano barrage. It would appear in this case only necessary that more glass balls should be used to keep the top of the nets at the correct depth.

     It would require time to get the net laid, owing to the inevitable delay in assembling the material and the fact that it could only be laid in fine weather.

     The Italian Commander-in-Chief9 had pointed out that, in view of the length of time it would take to complete the second barrage and the fact that there appeared to be mines available that could be moored at a few hundred fathoms, it would be advisable to lay minefields in the Lower Adriatic, so as to restrict the area through which submarines could pass. These minefields would also assist the hunting craft.

     The following minefields, extending from the coast, were thought desirable:-

     One from S. Maria di Leuca, 20 miles long, which meant to say that the outer end of the line would lie in about 200 fathoms. The first five miles of this field were now being laid with Service mines. The mines to be laid should be moored at a depth of 20 metres from the surface so that all surface craft could pass over them.

     The second field should be placed at San Cataldo di Bari, stretching in a north-easterly direction and extending for a distance of 15 miles to a depth of about 200 fathoms.

     The third minefield from Saseno, running west for about ten miles.

     No other minefields were considered necessary in the Adriatic.

     REAR-ADMIRAL RATYĖ then declared that in his opinion there had never been a question of greater urgency than that of completing the barrage across the Straits of Otranto, except, perhaps, that dealing with the mining of the Dardanelles.

     The completion and reinforcing of the Otranto Barrage was of the first importance. It was evident that if it was to be effective, it should be reinforced on the top as well as below. The only method of closing it on the top was to tow de Quillac mines.

     It was very necessary to hasten the manufacture of all material so that the Barrage could be completed before September, when the bad weather set in. The depth of the net was 50 metres, and as the top of the net was ten metres from the surface the net only extended to a total depth of 60 metres from the surface. Submarines could of course dive below this, and to meet this difficulty he proposed to supplement the fixed barrage by mooring mines beneath it.

     Admiral Ratyé advised that we should, at all costs, concentrate our efforts on this Barrage before attempting barrages in other localities in the Mediterranean.

     CAPITAINE DE VAISSEAU FROCHOT then said anti-submarine barrages were such costly things and took so much trouble to make, that they should be thoroughly efficient, otherwise they were not worth the money spent on them. They ought to be so constructed that submarines could not dive underneath them. A distance of 33 feet from the top of the net barrage was too great; at that depth submarines could just pass below the surface without coming in contact with the top of the net. He was of opinion that the top of the barrage should not be more than 26 feet below the surface. At present not only could submarines pass over the barrage, but they could also pass underneath the de Quillac mines.

     He did not think that there was sufficient swell in the Straits of Otranto to interfere with the buoys at this depth.

     The question of battleships having to pass through the barrage had to be considered. If it was necessary to move large ships at any time through the barrage it would be quite simple to sweep a passage with ordinary sweepers.

     All navigation at night should be stopped in the vicinity of the barrage in order not to interfere with the towed mines, and to prevent the possibility of neutral ship passing over the barrage with intent to destroy it, which could easily be done by a neutral ship towing an explosive charge.

     As regards the scheme of laying a second barrage, he was of opinion that it should be near and parallel to the first, so that the same surface craft could look after both, otherwise the difficulties of providing sufficient patrol craft would be too great to deal with.

     As regards the lines of mines that had been proposed he did not like their position, and thought they should all be near the barrage, so that again one organsation could extend over the minefields and net barrages. It must be remembered that it was impossible to lay lines of mines without the enemy knowing everything about them in a very short space of time, their depth, position, etc. In summing up he urged a big concentration in one locality, and in this case all the other minefields suggested were unnecessary.

     REAR-ADMIRAL STRAUSS agreed with Admiral Ratyé that the Otranto Barrage was of great importance. He did not believe in wing minefields and considered that no minefield was worth anything unless it was a complete barrier. He believed that they could handle a mine barrage between Cape Orso and Saseno Island with their present mine, that was, if depths of not more than 500 fathoms were encountered.

     REAR-ADMIRAL RATYĖ then said that with regard to the question of the barrage in the Straits of Otranto a problem of very great difficulty was originally set, when immediate successful results were not expected, but now it could be said that the problem had been largely solved.

     The whole point appeared to be that at present it was impossible to lay mines at the depths obtaining in the Straits of Otranto, but it had been proved that fixed barrages could be successfully laid. There seemed to be no question of choice as to the desirability of fixed barrages in the Straits of Otranto. We could as yet construct no other form of mined barrage.

     The PRESIDENT then asked Admiral Strauss to give his views on the general position before going into any further detail.

     REAR-ADMIRAL STRAUSS said he had received a dispatch that morning that made him think it possible to lay mines across the Straits. The Otranto net barrage was nearing completion and it would be desirable to go on with it, especially as it had given some success.

     The Americans would have to carry out some experimental work before they could complete the scheme by means of mines laid in the deepest parts of the Straits.

     REAR-ADMIRAL RATYĖ entirely agreed with Admiral Strauss.

     REAR-ADMIRAL STRAUSS said he assumed the United States were prepared to go ahead and lay a mine barrier across the Straits of Otranto. He fancied that they might not start work for a couple of months, because the Navy Department wished to complete the present scheme in home waters before starting a new one. He had been informed by the department that day that they could take care of depths not exceeding 500 fathoms, and the question was one of the capacity of the mooring reel in the mine. By using a superior steel, they could increase the amount wound on to this reel. At the same time, they were going on experimenting at 600 fathoms. There might be reasons forbidding mining in as great a depth of water as that. He did not know whether anyone present had experience on the subject.

     CAPTAIN LITCHFIELD SPEER said that Great Britain had not attempted it yet. The chief difficulty was the question of tide and buoyancy. In depths of 500 fathoms it was necessary to have a lifting buoyancy in the mine of at least 500 pounds, to support the weight of the mooring rope alone. This might mean a very large mine. Except in still waters mining in depths greater than 300 fathoms was a doubtful proposition. Under 300 fathoms only a very small tide was permissible.

     REAR-ADMIRAL STRAUSS said he referred to difficulties affecting the mine after it had been laid in 3,000 feet. Did any one know of any reason why a mooring rope of 3,000 feet long should not be possible? If not he should advise going right ahead. It required, he thought, about 16,000 mines to cross the Otranto Straits, going from Otranto to Fano Island and then down to Corfu. It would take about 11,000 mines to go into water that we are not at present prepared to mine in. The Orso-Saseno Island route had the advantage of allowing them to go right ahead with the mining. The amount of water was not sufficient to bar mining with the new mooring rope. The proposition he had to make was that they should approve the Otranto-Fano barrier being completed and that they should supplement it by a line of mines from Orso Point to Saseno Island.

     The Conference adjourned till the afternoon.

2nd Session--Afternoon, 6th August.

     The PRESIDENT said that it was proposed to examine the question of all other minefields and barrages mentioned on the Agenda paper. He thought that if they finished the discussion on the Straits of Otranto before they discussed any of the other possible barrages, they might find that they had committed themselves to conclusions, and then be sorry that they had not gone into the needs of other localities sooner; and so, what he suggested was that they should, in grand committee, go through all these barrages one after the other, then split up into three sub-committees, which should meet on the following day to go into details, and on the third day the sub-committees would report the conclusions they had come to. He had consulted the Admirals on this matter and it was now proposed to appoint these sub-committees as follows:-

One to deal with the question of the Dardanelles; another to deal with the Otranto Barrage and the Cape Bon-Sicily scheme; and the third committee, barrages in the Ægean.

          This was agreed to.

(Vide Appendix 2-Composition of the Sub-Committees.)

Minute 3 (b) of Agenda.

     The PRESIDENT then said they could pass on to the second barrage mentioned in the Agenda, viz., Sicily-Cape Bon. The distance between Cape Granitola and Cape Bon in Africa was about 80 miles, and a complete barrage would entail one or two miles of depths of over 200 fathoms. He understood that this barrage would be laid by the United States, and he would call upon Admiral Strauss to express his views.

     REAR ADMIRAL STRAUSS said that his idea was to do the first work there, that was between Cape Bon and Sicily, as the means for this were all ready. The United States had, he believed, about 9,000 Elia mines which could be devoted to that purpose. Laying the mines 75 feet apart would allow 80 mines to the mile, and the number required for approximately 80 miles would be 6,400. When he mentioned 9,000 mines he was speaking from personal recollection, but he understood from a despatch which he had received that day, in which it was stated that the department had the necessary number of Elia mines ready, that they had more than enough for two depths at the distance apart he had mentioned. These mines could be disposed of in that Strait just as quickly as the minelaying vessels could be obtained. In this despatch it was also stated that the first American effort to be made should be laying of the mines between Cape Bon and Sicily and he agreed with that. By this scheme the Mediterranean was cut into two, vessels navigating in the western half being free from submarines based in the Adriatic, while submarines in the eastern half would be unable to return to Germany. He therefore attached great value to the scheme and regarded the mining from Cape Bon to Sicily as a primary measure. They could then get on to the next most important, i.e. the Adriatic. Of course, in all these schemes it was necessary to provide means to allow our own and neutral shipping free passage through the minefield, and this would be ensured by means of gates. The possibility of submarines getting through the Straits of Messina had, of course, to be considered. He understood that submarines were now using the Straits of Messina, but it seemed to him that it would be very easy to make a barrier there.

     The PRESIDENT said that the British possessed no information that any enemy submarine had ever been through the Straits of Messina. It was known that they had approached one end or the other and there had attacked traffic, but not that they had ever gone right through.

     REAR-ADMIRAL SALAZAR and CAPITAINE DE VAISSEAU FROCHOT expressed the opinion that submarines had gone through the Straits of Messina occasionally.

     REAR-ADMIRAL STRAUSS said that whether or not the submarines had actually gone through, the possibility of their getting through the Straits submerged had to be considered.

     The questions of current and consequent dip of mines in these straits were then discussed, Rear-Admiral Strauss expressing the opinion that, if mines could not be laid in the two-mile stretch across the Straits on this account, there was quite good mining water five miles North of the Straits, where the current was slack and the depth of water did not prevent minelaying. He could see no difficulty in getting a complete barrier across there.

     Returning to the question of the Cape Bon-Sicily barrage, the President asked what would be required in the way of patrol for a minefield such as Admiral Strauss had suggested, explaining that, in this part of the Mediterranean, there were no surface craft which could come and attack our barrages and that we needed only to consider enemy submarines. We had absolute control of the sea on the surface there.

     REAR-ADMIRAL STRAUSS thought that four sentry patrols on this 80 miles stretch would be sufficient.

     REAR-ADMIRAL SALAZAR asked if this barrage was intended to extend to the surface.

     REAR-ADMIRAL STRAUSS said that the mines for the Cape Bon-Sicily field were primarily a surface barrage. He was not at all certain that the United States would not be able to give other mines besides their stock of Elia mines. He knew that if they undertook a barrier in that place they would supply sufficient mines to make it effective, i.e. a barrier extending from the surface.

     REAR-ADMIRAL SALAZAR remarked that if surface mines were put across from Cape Bon to Granitola and across the Straits of Messina, mercantile traffic would be interfered with.

     The PRESIDENT then called on Commodore Baird to give his opinion on this question.

     COMMODORE BAIRD said that firstly, Bizerta--Malta convoys and vice versa passed through that area every five days; that meant twelve of these convoys going through each month: Secondly, the Bizerta--Alexandria and vice versa convoys, of which fifteen passed monthly. Thirdly, the H.E. (Homeward Eastern) and O.E. (Outward Eastern) and Troop convoys, making a total altogether of thirty-five convoys each month. Besides this, there was the coastal traffic on the Sicilian and African coasts. This coastal traffic would require a gate off Cape Bon, and one somewhere on the other side, and so far as he could see, the main traffic would require two gates further out. The question of the width of the gates would have the be considered. He could not guarantee to work his convoys in such a way that they would be able to pass through in daylight hours, and under these circumstances, after a good deal of consideration, he thought four broad gates would be required through which to pass convoys. To pass a convoy through a gate in single line ahead would require two hours, including the time required to reform a convoy after passing through the gate. This interval would be one of great danger.

     REAR-ADMIRAL STRAUSS asked Commodore Baird what he considered the width of the gate ought to be.

     COMMODORE BAIRD stated he considered it should be a mile and a half to two miles.*10

     Summarising, he said that what was required was four gates, one at the Western end, one at Cape Granitola, and two others somewhere on the Adventure Bank.

     REAR-ADMIRAL RATYĖ questioned the advantage of cutting the Mediterranean in two by a minefield. He asked if it were not better to block the channels through which all submarines had to pass when proceeding to and from their bases. These channels were to be found in the Straits of Otranto, the Dardanelles and the Straits of Gibraltar. The problem would be entirely solved if we were to block these, and this being so, there would be no necessity to mine other places. He entirely agreed with Commodore Baird as to the difficulty of ships finding the gates through a barrage from Cape Bon to Granitola, and he thought that in foggy and bad weather ships would undoubtedly miss the gates and be blown up on the minefield. He again emphasised the necessity for barring the three areas he had already mentioned, doing that thoroughly and not complicating our efforts by laying minefields elsewhere in the Mediterranean.

     REAR-ADMIRAL SATO asked if it were possible to lay a deep minefield at 60 feet in the Cape Bon-Sicily area.

     The PRESIDENT stated that it was not impossible but was against the principles enunciated by the Allied Naval Council.

     REAR-ADMIRAL STRAUSS stated that he agreed with the principle laid down by the Allied Naval Council. The effective patrol of 80 miles was a hopeless proposition and mines must reach the surface if we were to to expect any results. There was the choice of destroying the submarine, or the remote accident of falling foul of our own field.

     REAR-ADMIRAL SATO concurred that if it were necessary to make gates it would be an advantage to make four as proposed by Commodore Baird.

     REAR-ADMIRAL RATYĖ stated that the great handicap always found in routeing traffic was to prevent it concentrating at narrow places. In the case of this minefield, a few gates would present these very difficulties, and either more gates would have to be made or we would be suffering from the evil we had always tried to avoid. He suggested that it would be easy for a submarine to follow a convoy through the gates. He did not see the advantage of dividing the Mediterranean in two, and there would thus still be two large areas in which submarines could work, partly from the Atlantic and partly from the Adriatic.

     REAR-ADMIRAL SALAZAR stated that he held the same views as Admiral Ratyé on this question. He did not see the advantage of cutting the Mediterranean in two in this manner; and he considered there were many drawbacks to this scheme, and that the mines could be better utilised elsewhere.

     CAPTAIN LITCHFIELD-SPEER asked if it were possible to route convoys through the Straits of Messina. It was possible, by changing the gates in the Cape Bon barrage, to overcome the objection raised. The moral effect of the barrage would always remain. He thought the objections raised could be overcome.

     The PRESIDENT said that with reference to Captain Litchfield-Speer’s question, in the opinion of Commodore Baird, it was out of the question to route convoys through the Straits of Messina.

     The President then said he thought the question had been sufficiently discussed to pass it on to the sub_committee, and the Conference would now proceed to deal with minefields and barrages in the Ægean.

     The PRESIDENT asked Admiral Ratyé to open the discussion on the question of the barrages in the Ægean.

     REAR-ADMIRAL RATYE said that the question of the Ægean barrage was a double one, the same could be said of the Straits of Otranto. It should be capable of stopping surface ships as well as submarines. As he had mentioned before, there were only three places whence the submarines came-the Adriatic, Gibraltar and the Ægean, through the Dardanelles. If the immediate danger was the Straits of Otranto, it would soon be in the Dardanelles, as the Germans had now got all the good bases offered by the Black Sea Ports. If the Commission was to do its work thoroughly it must consider not only present dangers but those that would arise shortly. He quoted a report about the Kaiser who was said to be anxious as to the safety of his submarines working from the Adriatic and to have the intention of changing the bases from the Adriatic elsewhere. This report might be accepted, as the intention expressed was just what we should expect the enemy to do. It was necessary to tackle the Dardanelles as soon as possible. His opinion was that the minefields around the Dardanelles themselves were not sufficient to prevent submarines proceeding into the Eastern Mediterranean, and that minefields in the Ægean Islands must also be established. The great difficulty about the minefields close to the Dardanelles was the fact that they touched an enemy coast which was highly fortified. The Military Base at Salonica opened up another question as regards mine protection in the Ægean. Every endeavour was now being made to make a safe route from Italy through the Gulf of Patras to Salonica and thence through the Straits of Eubœa. The Allied Commander-in-Chief was extremely anxious about this, and it therefore seemed necessary that the Commission should study this question. Another point was that ships at Mudros were at present confined to the harbour and had no opportunity of proceeding to an open stretch of water and carrying out exercises; therefore, minefields should be laid with a view to the provision of such an area. He thought that priority of minefields in the Ægean should be as follows: Mudros Minefield, minefields or barrages protecting the Straits of Eubœa, i.e., in the Trikiri Channel between Cape Griva and the north coast of Eubœa, and minefields or barrages in the Cyclades.

     REAR-ADMIRAL STRAUSS stated that he had considered the question of a minefield in the Ægean and could possibly do what Admiral Ratyé required. He suggested a minefield starting at the Doro Channel and Steno Pass, passing then between Tinos and Mykoni, across to Nikaria, then E.S.E. to Furni, and then N.E. to Samos. It involved making use of 16,000 mines and 4,000 to 5,000 deep mines, all other mines being laid to fulfil the conditions of the Allied Naval Council.

     The PRESIDENT then suggested in view of the Ægean requirements having been broadly discussed, that the question of the Straits of Gibraltar should now be taken.

     The PRESIDENT said that he had no definite instructions from the British Admiralty on this particular question. He did not know whether it had been studied from a diplomatic point of view, and it might be that the Powers would object to running a barrage to a neutral coast. He suggested, nevertheless, that the Commission should discuss the matter, as it was mentioned at the Conference of Rome in February last.

     REAR-ADMIRAL RATYE said that if the barrage at Gibraltar was really considered to be an important one, experiments should be undertaken as soon as possible in these waters to see what could eventually be done. As regards the diplomatic situation, that had been largely altered recently.

     REAR-ADMIRAL SATO said that he thought that the question of a barrage in the Straits of Gibraltar was a very important one, whatever the diplomatic point of view might be.

     REAR-ADMIRAL STRAUSS said he understood there was a five to six knot current through the Straits, and that, in view of the great depth, it offered undoubted difficulties.

     CAPTAIN LITCHFIELD-SPEER considered that if a minefield was established it would have to be laid well to the westward, probably between Cape Spartel and Cape Trafalgar. It would then be clear of the strongest tides, and in shallower water than it would be if placed in the Straits.

     REAR-ADMIRAL STRAUSS stated that this would take the minefield into Spanish territorial waters.

Minute 4 of the Agenda.

     The PRESIDENT asked whether any of the delegates could suggest any other minefield or barrage which would seem worthy of discussion.

     REAR-ADMIRAL SATO thought the question of a barrage in the Malta Channel ought to be considered.

     REAR-ADMIRAL RATYE suggested, as an additional barrage to those already mentioned, one which the Allied Commander-in-Chief was extremely anxious to have established, namely, minefields guarding the route from Italy through the Gulf of Patras to Salonica. A small barrage from Cape Dukato to Cephalonia and a barrage from Cape Monda in Cephalonia to Cape Glarenza on the Greek coast, which would completely shut in the entrance to the Gulf of Patras, were suggested as being necessary to this scheme.

     He further suggested a minefield in the neighbourhood of Port Said.

     The PRESIDENT remarked that the arrangements as to this latter were already practically completed.

     REAR-ADMIRAL RATYE also proposed for consideration the laying of barrages between Cape Corse, Elba, and the Italian coast.

     REAR-ADMIRAL SALAZAR said that he was not in favour of the proposal. The matter was not further discussed.

     The PRESIDENT now moved that sub-committees should be nominated. He suggested that there should be three sub-committees. That the first should go into the question of the completion of the minefields off the Dardanelles. It was a question which chiefly concerned the French and English as the mines to be laid there would probably be entirely French and English.

     That the second should deal with questions of barrages in the Adriatic and the area between Cape Bon and Sicily.

     That the third should discuss the requirements of the Ægean.

     (For the composition of these sub-committees see Appendix 2).

     The Conference having agreed, the President asked that the sub-committees should present their reports to the Conference on 8th August.

     The Conference then adjourned.

3rd Session--Afternoon, Thursday, 8th August.

     The PRESIDENT opened the proceedings by referring to the Dardanelles Report handed in by the sub-committee (vide Appendix 3). According to this report the sub-committee considered that when the mines now available for this purpose had been laid, they would have 4,000 mines in the water, and this number they appeared to consider sufficient. They wanted, however, over and above that, the reserve of 1,500 originally proposed.

     REAR-ADMIRAL RATYE said that the Conference had confined its attention to surface craft and he now proposed that the Conference should consider anti-submarine measures off the Dardanelles, as enemy submarines were sure to commence using the Black Sea Ports.

     The PRESIDENT said he thought that question was included with the other proposals of the sub-committee dealing with the barrages in the Ægean generally. The question as to whether the area close to the Dardanelles could be effectively mined against submarines was rather uncertain because it was thought that the enemy could sweep passages along their own shore under their batteries, thus allowing submarines to pass easily into deep water. It was understood that the big barrage further south had been proposed as the best way out of the difficulty. After some further discussion the Conference decided on the following recommendation:-

Final recommendation on Minute 1 of the Agenda.

     The Conference recommended that the re-establishment of the Dardanelles minefield should be proceeded with in accordance with the proposals of the sub-committee, the mines being supplied by France and England. They also recommended that a minefield against surface ships and submarines should be laid between Imbros and Cape Gremea when suitable mines became available.

Report of the Sub-Committee on the Mining of the Ægean

     The Secretary then read the report of the sub-committee on the mining of the Ægean (vide Appendix 4).

     It was decided to discuss the main barrage across the Ægean first, and afterwards the question of defence of the Italy-Salonica route.

     The delegates were asked if they agreed to the main principle of the Ægean Barrage.

     REAR-ADMIRAL SATO said that he thought this barrage was not a very important one. He agreed to its establishment if the other and more important barrages in the Mediterranean were not thereby prejudiced.

     The report of the sub-committee was then discussed. As regards par. 4 of Article II. of the sub-committee’s report:-

“4. It is considered that there should be one gate only in the deepest water in the Doro Channel. If, subsequently, other gates are found necessary they can easily be arranged for.”

     REAR-ADMIRAL STRAUSS objected to the clause “If, subsequently, other gates are found necessary they can easily be arranged for.” He said that this would leave the whole subject “in the air,” and suggested that it would be as well to get used to the idea of one passage, which could be efficiently defended and patrolled. He would like to see the principle of the complete barrage upheld.

     REAR-ADMIRAL RATYE was desirous of keeping to the wording of the sub-committee’s report and not altering it.

     REAR-ADMIRAL STRAUSS said that he would like to point out that barrages of this sort were tremendously costly in money and in effort, and they should be undertaken only on the understanding that they were permanencies as long as the need for such barrages existed, and that they should not be lightly injured at the desire of any nation; according to the report of the sub-committee, the United States was the nation suggested to lay this barrage and in this case the United States wanted to feel that they had laid a useful barrage and not one the continuity of which could be broken by anyone who desired to do so. He proposed that if it was found necessary to make another gate through the barrage in the event of military necessity, such a passage could easily be swept; but it would have to be closed immediately the war vessels using it had passed through.

     It was agreed that a clause covering this proposal should be inserted in the recommendation.

     As regards paragraphs 5, 6 and 7 (vide Appendix 4):-

     REAR-ADMIRAL RATYE said that surface craft had been arranged for, but no provision had been made for aircraft. He said that the gate in a barrage would be a place used by submarines as an ambush, also that they would lay mines in the vicinity. He was therefore strongly of opinion that aircraft should be used in the vicinity of any gate through a barrage.

     As regards paragraph 10, the Conference agreed that Great Britain should supply the patrol craft to look after the barrage, as the zone was a British one, and that such craft should come under the orders of the United States Officer in charge of the barrage.

     As regards paragraph 12, it was agreed that this question could only be settled by the Allied Governments.

     As regards paragraph 16:-

“It is considered that the establishment of a separate base in the Ægean for this project will not be necessary, but that use should be made of the main base established in connection with the other mine barrage proposals under consideration.”

     REAR-ADMIRAL STRAUSS said he could see no military objection to the United States selecting a base in any Allied country in which they could make the necessary arrangements.

     Article III. of the Report of the Sub-Committee was read by the Secretary.

     REAR-ADMIRAL RATYE again emphasised the need of aerial patrols in the vicinity of gates through barrages.

     Article IV. of the Report of the Sub-Committee was then read.

     REAR-ADMIRAL STRAUSS said he did not think it was worth while seriously considering the scheme. It was stated in the report of the sub-committee that they doubted its utility.

     REAR-ADMIRAL RATYE said that the barrage in question was not of the same strategical importance as the others they had discussed, but he attached great importance to guarding the line between Italy and Salonica, as, in the event of our being attacked at the latter place, it was important that we should be able to send reinforcements as quickly as possible.

Final recommendations of the Conference on Minute 3 (c) of the Agenda.

     1. It was considered that it was desirable that there should be a complete anti-submarine barrage in the Ægean Sea to comply, as far as possible, with the principles laid down by the Allied Naval Council.

     2. It was considered that the mine barrage, No. 4 of the Barrages in the Ægean, in Memorandum No. 168 of the United States of America, was the most suitable that could be suggested.

     3. It was considered that there should be one gate only in the deepest water of the Doro Channel. If subsequently under military urgency it was found necessary to sweep an opening for the passage of a fleet, it could be done, but such opening was not to be maintained as a gate, and was to be closed at the earliest opportunity.

     4. The gate should not be less than 500 nor more than 1000 yards in width and should be free for passage of vessels on the surface only. It would require to be guarded by day and night to prevent the passage of submarines on the surface.

     5. Two tugs and six trawlers would be required to control the traffic, to pass sailing ships through, and to reinforce escorts in the immediate vicinity of the gate in the Doro Channel.

     For the channels between Andros, Tinos, Mykoni, Nikaria, Themina, Furni and Samos, seven vessels would require to be constantly patrolling, involving a total requirement of twelve vessels.

     6. For the mine barrier between Samos Island and Cape Kanapitza, two watching vessels would be required, i.e., a total of three.

     7. Aircraft should be largely used for watching the gate and the channel between Samos Island and Cape Kanapitza.

     8. It would be necessary to maintain a sufficient armed force at Samos to prevent the enemy obtaining control of both sides of this channel.

     9. It was considered that the responsibility of the provision, laying and maintenance of the minefield should be entirely in the hands of the United States of America and that the method of laying and details of plans should be left to the Government responsible for executing the project.

     10. It was considered that Great Britain should furnish all the above craft, as the zone is a British one.

     11. The patrol vessels should be under the orders of the United States Senior Officer of the barrage.

     12. The allocation of the responsibility for the provision of the land forces indicated as necessary for the defence of Samos should be decided by the Allied Naval Council.

     13. It was observed that if this project was put into execution the coastal and inter-island shipping would be largely interfered with, that this was a matter which principally affected the Government of Greece, and that this question should therefore be taken up with that country at the earliest moment possible in order that their concurrence and co-operation might be obtained.

     14. It was suggested that a passage for small craft such as caiques, would be possible in the Eastern Ægean in the Furni-Boghaz, which has a width of less than 100 yards and could be closed by a net.

     15. It was considered that the establishment of a separate base in the Ægean for this project would not be necessary but that use should be made of the main base established in connection with the other mine barrage proposals under consideration.

     16. Barrages guarding the Northern and Southern entrances to the Eubœan Channels should be proceeded with but Barrages in the Gulfs of Petali and Athens were not essential. Those between Cape Dukato and Cape Vlioti and between Cephalonia and Cape Glarenza should only be considered after the main Ægean Barrages had been laid.

     Article V. of the Report of the Sub-Committee was then read. This referred to the question of mining the Straits of Gibraltar.

     REAR-ADMIRAL SATO said he considered this an important barrage and asked Captain Litchfield-Speer for his views as to its practicability.

     CAPTAIN LITCHFIELD-SPEER said he considered mining in any depth exceeding 300 fathoms was probably impracticable, except in very still water. He did not think there would be much hope of mining the Straits. Were it possible to get into neutral waters something might be done further to the west.

     REAR-ADMIRAL RATYE thought the tidal conditions in the Straits of Gibraltar should be investigated, as it might be found that certain places would offer less difficulty than others as regards placing a barrage. He considered it extremely important that this should be done.

Final recommendation of the Conference on Minute 3 (d) of the Agenda.

     The Conference recommended that the possibility of a barrier in the Straits of Gibraltar should be investigated.

4th Session--Morning, Friday, 9th August.

     The conclusion arrived at on the previous day on the question of mining off the Dardanelles was slightly altered. The final recommendation of the Conference was now as given at the conclusion of the discussion on the subject (see page 11 and “Recommendations”).

Report on the Sub-Committee on the Barrages in the Adriatic.

     The PRESIDENT proposed that Admiral Salazar should give the ideas of his Government on this subject and afterwards Admiral Ratyé those of France.

     REAR-ADMIRAL SALAZAR said he had been authorised by the Chief of Staff of the Italian Navy, Admiral di Revel, to accept the American principle that the mine barrage should extend to the surface.

     In this case, however, it was absolutely indispensable, in order to assure the freedom of movements of the Italian Battle Fleet and for other reasons which could easily be appreciated, that this barrage should be placed between Cape S. Maria di Leuca and Fano and no further north than that, and that it should have two gates, one on the Italian side and one near Fano.

     The Italians were of opinion that in view of the special design of American mines, by which their safety was assured when they broke away from their moorings, the placing of this barrage from one side of the Adriatic to the other would not interfere with the necessary freedom of movement of Allied ships.

     The distance between Cape S. Maria di Leuca and Fano was 46 miles. It could approximately be said that only in the last eight miles approaching Fano were depths met with in which more than 600 fathoms obtained.

     Such being the case, they hoped that the Americans would commence to lay this barrage as soon as possible without waiting for mines that could be laid in depths greater than 500 fathoms.

     Another important observation to be made as regards the conclusions of the sub-committee was that it was essential to complete the present fixed barrage and then to commence the second fixed barrage, the nets of which should extend to a depth of 100 metres.

     Therefore not only was it necessary to prepare the material, as recommended in paragraph 4 of the sub-committee’s report, but it was important to commence placing this second fixed barrage without waiting to overcome the difficulties of placing such a barrage in depths greater than those already met with.

     The importance to the Allies of closing the Straits of Otranto was so great that no delay should be permitted in carrying out this project.

     Every effort should be made to act without loss of time, and to foresee and provide for the difficulties before they arose.

     The PRESIDENT asked Admiral Salazar whether, in the event of it being decided to place a mined net barrage from S. Maria di Leuca to Fano, it would not be better to start it from a place somewhat further north than the former place, say Tricase.

     REAR-ADMIRAL SALAZAR saw no objection to this. The depth of water, however, on the S. Maria di Leuca-Fano line offered the best facilities.

     The PRESIDENT then asked Admiral Salazar if he agreed to the two mined net barrages being reasonably close to and parallel to one another. This was suggested with the idea of economising patrol craft.

     REAR-ADMIRAL SALAZAR said that though there were certain drawbacks, the fact that such an arrangement would economise patrol craft made the argument a sound one, and he would lay it before Admiral di Revel.

     REAR-ADMIRAL STRAUSS asked whether the space between Fano and Corfu was effectively closed at present, and if so, how was it guarded?

     REAR-ADMIRAL RATYE replied that there was a small passage east of Fano from 300 to 400 yards wide, guarded by drifters. Submarines however never passed there. The obstruction between Fano and Corfu consisted of a net from the surface to the sea bed.

     The PRESIDENT then asked if Rear-Admiral Strauss what he knew about the proposal as to the second net barrage. Had America engaged to lay a very large minefield, as well as to undertake to assist the establishment of a second net barrage?

     REAR-ADMIRAL STRAUSS replied that he had no instructions as to the United States doing anything towards the construction of a second net barrage. As far as material went they had large reserves of wire, etc., but there was a limit, and they were manufacturing a very large number of mine moorings, which meant a big output of steel wire, and, therefore, they should be permitted to have some say as to what use their wire should be put. In view of the fact that they did not believe that this net was a sufficient barrier in comparison to the minefield they wished to lay, they considered that their first efforts should be towards providing mooring ropes for the mines that would be required for this minefield.

     REAR-ADMIRAL RATYE was then asked to state what the French opinion was with regard to the Otranto barrage.

     He replied that what impressed him most was the imperative necessity of completing the first barrage before anything else was started, as he feared that the German submarines would leave the Adriatic and base themselves on the Black Sea ports, and therefore it was essential to blockade the submarines in the Adriatic now.

     After September he did not think there would be any serious work undertaken in the way of laying barrages until the following spring. He did not wish to see the second net barrage started until the first was completed. The Admiralties of each Government should be impressed with the necessity of preparing all material and supplying it as soon as possible. The way to finish the present barrage was to complete it, underneath with deep mines, and on the top by towed de Quillac mines. He also thought that in addition to these measures, deep minefields should be laid in the shallower water on each flank of the barrage.

     The next question to be considered was what should be done when the first net barrage was completed. The second net barrage should certainly be placed, but he was extremely anxious that it should be placed at not too great a distance from the first, as he considered it of the utmost importance that the patrols and organisation should be simplified. He thought that two net barrages, fairly close together, were much more efficacious than a barrage in the Straits of Otranto, and another, say, half way down the Mediterranean. Another point he wished the Conference to consider was that in the winter months the patrol craft looking after the barrage should not be at a great distance from a convenient base.

     He again emphasised the great importance of giving first place to the completion of the present barrage and insisted that every effort should be made to close the Straits of Otranto completely before anything else was done. He said that when the first net barrage was completed, a second should be placed, and when that was completed, a third, and then after that perhaps one might think of other barrages outside the Straits. In his experience of officers who had studied this matter during the course of the war, all had seen the great strategical importance of closing the Straits of Otranto.

     The PRESIDENT asked Admiral Ratyé if he recommended that the United States should be asked to lay a deep minefield underneath the present barrage.

     REAR-ADMIRAL RATYE said not necessarily directly underneath it, but parallel to and below it, in order that part of the water should be blocked.

     REAR-ADMIRAL SATO said he thought it very necessary to use both the Franco-Italian net and the American mine barrage side by side. He thought the work should be completed before the winter, otherwise it would take a considerable time to complete.

     REAR-ADMIRAL STRAUSS said, taking first the question of supplementing the Franco-Italian net with American mines, he thought it could be done, but of course they must have a mine which would be useful at that depth. The Franco-Italian net was laid in a depth at which they were not prepared to mine. He thought they were willing to do what they could, but be believed in the mine barrage. They were absolutely unwilling to lay mines for any distance whatever unless they were sure that the barrage, of which the mines would form a part, could be completed. To run out as far as possible with the mines obtainable and then wait the development of a mine that would be good for more than 500 fathoms he would be unwilling to do. He recommended the acceptance of the scheme of the barrage from Santa Maria di Leuca, or somewhere to the North, and Fano Island, but much would depend on the width of the gate. Admiral Salazar had asked that there should be two gates. The question was how wide were these to be. If the report of the sub-committee was accepted they recommended gates with a width of five miles, this distance being possibly decreased in the future. If there were two of these gates they involved an opening, in a distance of 43 miles, of nearly 25 per cent. of the total distance. He considered a barrage of that sort worth nothing. He was willing to supplement the net so far as he was able with mines but he would like to lay the mine barrage from Italy to Fano Island, although it involved a doubt as to the success of mining in such deep water.

     REAR-ADMIRAL RATYE agreed with Admiral Strauss that the gates in barrages should be as narrow as possible and as few as possible. Night traffic should be stopped. He understood the United States would furnish the mines to finish the present barrage and mines to establish a mine barrage.

     The PRESIDENT asked if it were possible to place a second net underneath the first one on the Otrano-Fano Barrage.

     CAPITAINE DE VAISSEAU FROCHOT did not think it possible to add nets to the ones which were at present laid, as he was certain that divers, who have to place these nets on the jackstays between the buoys which are below the surface, could not work at a depth greater than 20 metres. Two nets of the present size might be put together and then placed, but this was a matter for experiment.

     REAR-ADMIRAL SATO thought there should be only one gate in the barrage.

     REAR-ADMIRAL SALAZAR did not press for two gates.

     Some discussion then took place on the question of the safety of American mines that had broken adrift.

     REAR-ADMIRAL SALAZAR said that Admiral di Revel had accepted the idea of the American minefield reaching the surface, as it was understood that American drifting mines were quite safe.

     REAR-ADMIRAL STRAUSS said that they could be expected to be reasonably safe, but one could never guarantee that a large amount of explosive on being struck would be perfectly safe.

     REAR-ADMIRAL SALAZAR mentioned that they were extremely anxious on the question of drifting mines in the Adriatic, in view of the fact that nearly all such mines were washed up on the Italian coast.

     The PRESIDENT said he was not quite clear whether the Italians accepted the American minefield only on the condition that they made a second net barrage.  

     REAR-ADMIRAL SALAZAR said that Italy gladly accepted the American offer to lay a complete mine barrage in the southern Adriatic. Both forms of barrages should be used to supplement each other.

     The fixed barrage had itself capable of withstanding winter weather, as a section of it had been tried in the Gulf of Taranto last winter.

     The advantage of a net barrage over a minefield was that the former covered a vertical area from a distance of 10 metres below the surface to 100 metres, while the latter did not completely cover such an area. Further, it would be the first time a minefield had been attempted in such deep water.

     He again emphasized the necessity of supplying the necessary material for a second mine net barrage.

     CAPITANO DI CORVETTA RUSPOLI said that Admiral Sims11 had informed a representative of the Italian navy when in London, that the United States would do what they could to assist with a second net barrage, and on the 17th July Admiral Sims had asked for specifications for material for this barrage.12

     The PRESIDENT said that his personal view was that the most important thing was first to make the Otranto-Fano net barrage effective. To do that, they had not only to complete it and double it in depth in places where mines could not be laid, but also to lay the American mines to reinforce it, that is to say, to close the space under it and as regards the gap between the top of the net and the surface, to close it by towing de Quillac mines on the surface. He had little faith in the practicability of towed de Quillac mines. It meant a great deal of danger to the drifters and patrols, and it was a question which would have to be gone into very carefully with the officers responsible for the present mobile barrage. It would stop the hunting vessels, as directly the de Quillac mine was towed in that locality, hunting could not be carried out. At the same time he did not think the fixed net would be completely effective without some form of mine being towed along the top.

     He thought the second thing was to lay the American minefield, and he preferred that, if it was finally decided to lay it from Cape Santa Maria di Leuca, it should start somewhat north of that place, as the state of the sea further inside the Adriatic would probably be more favourable.

     The third thing was to consider the possibility of laying a second net barrage. Perhaps he was prejudiced, but he did not think the Allies were justified in expending the enormous amount of material required for the second fixed barrage until it was seen what a winter would do to the first one. He hoped it would stand it and be a complete success. But it was as yet untried.

     It would be best to complete the Otranto-Fano net barrage by reinforcing it beneath with American mines and above, if found practicable, by some system such as the de Quillac towed mines. In addition to this there would be the American mine barrage. The two together should constitute a very large and effective barrier. As regards the gate he agreed with Admiral Strauss that only one gate could be made.

     REAR-ADMIRAL RATYE thought that the Otranto barrage should be completed on the following lines.

     He proposed that where the water was comparatively shallow no nets were necessary. That mines alone would suffice. Where the water was deeper, but not at its greatest depth, the present nets, closed on the top and below by ordinary moored mines, would meet all requirements.

     In the deepest water the net should be doubled and no mines would therefore be required underneath it. On the top, it would be closed by towing de Quillac mines.

     REAR-ADMIRAL STRAUSS said this proposal was too late so far as the first barrage was concerned. They had run out into deep water and there was no use in changing the scheme now. Something of the sort might be done in future fixed barrages. He said it was a pity that in all the discussions they had lost sight of a very simple solution and one that could be quickly completed. It involved, however, the Italian Government receding from the position it had taken up. He referred to the scheme which the American Government preferred above all others, viz.: to lay a line of mines from somewhere north of Otranto to Saseno Island, complete from the surface. The mines were ready: there was nothing experimental about it, and the barrage would be completed without the dubious expedient of towing de Quillac mines.

     CAPITAINE DE VAISSEAU FROCHOT said the de Quillac mines were well tried at Toulon, a submarine having been made to pass through the tow, and on every occasion of so doing the firing gear of the mines worked correctly. Experiments were then carried out in the Straits of Otranto with de Quillac mines towed by four British drifters. On the third night that these mines were towed one of them exploded. The explosion could only have been caused by some other vessel, as a great strain had undoubtedly come on the towing hawser when the mine fired. No patrol vessel was lost on that night and it was thought therefore that the obstruction must have been a submarine. On none of the occasions of the drifters towing these mines had any difficulty been experienced in handling their own mines or had they been in danger from them

     REAR-ADMIRAL RATYE said that if more powerful vessels were employed for towing purposes a longer tow could be used, and it was thought possible to tow a line of de Quillac mines of about 3,000 yards in length.

     The PRESIDENT said that the tow had not been tried in winter gales. The question was whether these mines could be towed by a drifter broadside on to an Adriatic gale. It seemed to him to be out of the question. There was only one other remark he would like to make about the de Quillac system and that was that the barrage which was laid by the French and Italians should be maintained by them, and that he did not think the British could be asked to supply vessels to tow this French device over a Franco-Italian net. If those who laid the Franco-Italian net desired to supplement it on the surface with this system, it was evident that they should supply the means of carrying it out.

REAR-ADMIRAL RAYTE said that France could not provide the vessels to tow de Quillac mines. He would like to point out that de Quillac mines were only really necessary in the deepest part of the Straits, which might amount to one-third the distance, because in the other depths mines could be laid that would reach to the surface.

REAR-ADMIRAL STRAUSS said he understood the efficacy of these towed mines was problematical, especially in heavy weather. On the other hand they knew that moored mines formed an effective barrier. He was assured from Washington that they could produce mines now that would cover the line from Otranto to somewhere about Saseno Island. It was his firm opinion that the best scheme for closing the Otranto Straits was to mine it thoroughly between Otranto and Saseno Island. There was no depth there exceeding 500 fathoms and the Department at Washington had assured him that they could mine up to that depth. All that was necessary was that the Italian and French Governments should yield their objections to restricting the space on the east by 30 miles. The primary object of the Allied efforts was to defeat the submarines and they should not lose sight of that fact.

REAR-ADMIRAL RAYTE said that Admiral Gauchet had telegraphed to the effect that the matter was one mainly affected the Italian Admiralty. His own view was the Conference had to decide and settle about the completion of the first barrage with every means possible before anything else was thought of.

REAR-ADMIRAL SALAZAR said that the barrage extending to the surface between Otranto and Saseno was against the ideas of the Italian Admiralty. He concurred in everything that Admiral Calthorpe and Admiral Ratyé had said as regards the Otranto-Fano barrage and he thought that it should be easy to come to an agreement as to its completion, with all the means available.

The PRESIDENT said there was one other objection to the French proposition of reinforcing the present fixed barrage with mines extending to the surface. If it were put into execution it would completely throttle the present mobile barrage and it would be necessary to do away with the latter completely, whereas, if the American barrage, which menaced submarines proceeding on the surface as well as below it, were placed where it was proposed, the hydrophone operations could go on and they would thus have one more means of attacking the enemy.

REAR-ADMIRAL RATYE wished to know if it was proposed to complete the first barrage with all the means at the disposal of the Allies and by utilising mines as well as the nets to make it effective, or whether it was proposed to consider the construction of the second mine barrage further north leaving the first barrage incomplete as it now was.

He also thought the feeling the Conference was that it would be extremely difficult to persuade the Italian Admiralty to accept a barrage so far north, and most of them thought the best that could be done at present was something rather on the lines of what he had suggested, namely to reinforce the fixed barrage by mines and lay the American barrage to the southward.

The Conference then adjourned.

5th Session--Afternoon, Friday, 9th August, 1918.

The PRESIDENT began by saying that he proposed, what was in some sense an attempt at a compromise, to discuss the subject in the following order :-

(i)  The present mine net barrage and the proposals as to its completion.

(ii) The proposed new mine barrage between Cape St. Maria

di Leuca and Fano Island

(iii)The possibility of laying a mine barrier between Otranto and Cape Linguetta if the objections at present raised could be overcome.

     (i) As regards the present mine net barrage. The question of reinforcing the unguarded water on top of the present barrage was discussed.

     REAR-ADMIRAL RATYE stated that in order to close the space on the top of the net, mines should be laid by the United States to within six metres of the surface of the water, which would allow patrol vessels to pass over. The present distance of 10 metres between the surface and the top of the fixed net was too great and allowed submarines to pass over it submerged.

     REAR-ADMIRAL STRAUSS agreed that submarines could pass over the net, but was not in favour of reinforcing the barrage in this manner. He added that it could not be guaranteed that mines could be laid at exactly six metres from the surface.

     REAR-ADMIRAL SALAZAR said, since it was not certain that mines could be moored so that they were at a depth of six metres from the surface, he thought that they should be brought up to the surface, and in this case the idea of patrolling above the net should be given up.

     REAR-ADMIRAL RATYE asked that his wish in this respect should be entered in the Minutes. He was certain that at night submarines could pass over the net despite the presence of hydrophone craft. He declared that much of the efficiency of the barrage would be sacrificed if this space was not closed.

     The PRESIDENT remarked that Admiral Ratyé’s reservations would be entered in the recommendations of the Conference.

     As regards the question of the top of the minefield, after some discussion CAPTAINE DE VAISSEAU FROCHOT said that the objection to a barrage that stopped at 10 metres from the surface was the facility offered to submarines to pass at night. It seemed that in depth of not more than 500 fathoms the barrage should come to the surface, and in the deeper water hunting craft should patrol as they do now.

     The PRESIDENT pointed out that if the net barrage was reinforced in two parts, one consisting of mines extending to the surface and the other consisting only of deep mines below the nets and allowing hunting craft to pass over the latter, not only would the barrage be incomplete as a fixed barrage but hunting craft would be unable to operate owing to the danger of the surface mines.

     At present the hydrophone patrol was dropping depth charges on or near submarines two or three times a week, and it seemed unsound to do away with a very effective anti-submarine measure and put something less effective in its place.

     REAR-ADMIRAL SALAZAR then said that as British vessels were patrolling and hunting in the area in question he would not press for surface mines, if the British saw therein serious objection.

     REAR-ADMIRAL RAYTE said that if the top of the barrage was reinforced, except where the water was too deep to lay mines, the de Quillac towed mines would protect this latter portion, which would only cover a distance of about 17 miles.

     REAR-ADMIRAL STRAUSS said that it was not worth expending so many mines on a portion of this barrage, if they could place a complete mine barrage 45 miles long elsewhere.

     (ii) The proposed new mine barrage between Cape S. Maria de Leuca and Fano Island.

     All the delegates were agreed on the question of this barrage, which would be placed by the United States and would extend from 3 metres to 85 metres below the surface. A single gate, not wider than 5 miles should be placed, this gate should be reduced in width, if it was found possible. Deep mines should be laid in the gate at a depth of 10 metres.

     The United States should furnish all material to lay the mines and maintain them, and be responsible for the patrol.

     REAR-ADMIRAL SALAZAR thought that a depth of 10 metres in the gate was too small. He suggested that battleships passing through should have a clear depth of 20 metres.

     After some discussion it was agreed that the deep mines should be laid at a depth of 12 metres.

     It was further agreed that should battleships wish to pass through the gate, the latter should be specially swept for them, if desired.

     (iii) The possibility of laying a mine barrage between Otranto and Cape Linguetta if the objections at present raised could be overcome.

     REAR-ADMIRAL STRAUSS said he thought this should be done. The advantage lay in the fact that the mines capable of being laid in this depth of water could be laid with the present design of mine.

     After discussion REAR-ADMIRAL SALAZAR said he was personally not in favour of it, but he would telegraph to his Government to ask their opinion, telling them of the advantage there would be in laying it at once, while the other line would have to be delayed on account of there being no suitable mines.

     The Conference then recommended, with a reservation by Rear-Admiral Salazar (shown at the end of the recommendations), as follows :--

     1. (i) The the present mine net barrage now being laid by Italy and France be completed as designed between Otranto and Fano Island and that the United States should reinforce it by laying deep mines to complete its efficacy as a barrage to a depth of 85 metres from the surface.

       (ii) Where the great depth of water does not permit of               mines of present types being laid, the depth of the              net obstruction should be increased to at least 85               metres.

       (iii) With reference to passage of submarines over the               top of the net, the Conference were not satisfied               that any present form of towed explosive obstruction              had proved effective in anything but fine weather and            that further experiments must be made before deciding           on this question. In the meanwhile the present mobile         barrage patrol should continue.

     Admiral Ratyé did not concur with the recommendations embodied in (iii.). He was of opinion that the space on the top of the nets should be guarded by moored mines or by towed de Quillac mines.

     2. That a mine barrage between Cape Santa Maria de Leuca and Fano Island or further north on the Italian coast up to Cape Otranto and across to Fano Island be laid by the United States conditional upon the successful production of a mine suitable for the depth involved. That this barrier extend from three metres from the surface down to a total depth of 85 metres. That a gate be left near the western end not exceeding five miles in length and to be narrowed in future, should experience warrant its reduction, such gate to be free of all mines down to a depth of twelve metres, but to be thoroughly patrolled by craft capable of fighting submarines and in sufficient numbers to compel the submarines to dive into the minefield. That inasmuch as the United States Government would undertake to finish the mines and lay them, the operation of laying, controlling and maintaining the barrage be under their jurisdiction.

     REAR-ADMIRAL SALAZAR agreed on the condition that when battleships have to pass through the channel, it may be swept to a greater depth.

     3. If however the strategical objections raised by Italy could be overcome, the Conference was of opinion that a complete mine barrier with suitable gate between Otranto and Cape Linguetta should be laid in preference to the one proposed between Santa Maria de Leuca and Fano Island. This would be done with the material already designed, as the water is shoaler, and moreover, the barrier would be less exposed to the sea.

     4. REAR-ADMIRAL SALAZAR did not concur in the mine barrier being placed in the position proposed above.

Minute 3 (b) of Agenda

     The conference then studied (b) of Minute III. of the Agenda on the question of a barrage between Sicily and the African coast.

     REAR-ADMIRAL STRAUSS said it was necessary to keep enemy submarine bases in the Mediterranean from being reinforced by more submarines from Germany. It was also necessary to hamper enemy submarines already in the Mediterranean and confine them to as narrow an area as possible. This Cape Bon to Sicily barrage was a simple scheme and particularly attractive from the fact that we already had the material with which to accomplish it.

     He wished to say that in all these questions many people forgot that our principal object was to overcome the submarine, and when they did think of this they often wanted to accomplish it without incurring risks.

     It was for the Conference to decide whether in this case the advantage gained was sufficient to compensate for the trouble and danger that would be caused.

     COMMODORE BAIRD then read a statement prepared by himself on this subject. (Vide Appendix 5).

     REAR-ADMIRAL SATO thought that measures which would interfere with the freedom of traffic must be seriously considered.

     REAR-ADMIRAL RATYE agreed with Commodore Bair that a barrage from Cape Bon to Sicily would create difficulties greater than the good that it would do. It seemed to him that if they barred the Straits of Otranto and the Dardanelles there was no need to place barriers elsewhere in the Mediterranean. In the rare event of a submarine coming from Germany it had to go to its base in the Adriatic, and there again the barrage in the Straits of Otranto would form an obstruction to it. Further, if the Cape Bon--Sicily barrage was placed, submarines would undoubtedly concentrate in the Eastern Mediterranean. He was firmly of opinion that when the Straits of Otranto and the Dardanelles were properly mined and if there was any more mining material available, such material should go to reinforce the barrages already placed in the Ægean and Adriatic.

     REAR-ADMIRAL SALAZAR said he thought a barrage between Cape Bon and Sicily would offer more dangers than advantages. He agreed with Commodere Baird and Admiral Rayté on the points they had raised.

     CAPTAIN LITCHFIELD-SPEER said what the sub-committee had had in mind was that it might be some time before effective barrages in the Ægean and Adriatic were completed. They had therefore recommended for the consideration of the Conference the question whether the advantages of the mine barrage were worth the disadvantages that would undoubtedly be caused to traffic. They also felt that if a barrage was laid at all it should be a complete one. A partial one would not be worth placing, and such a barrage would entail a large number of patrols and would not overcome all the objections which Commodore Baird had raised.

     REAR-ADMIRAL STRAUSS said that some objections had been raised which he did not think would stand investigation, but if 12 miles were required for gates the scheme was not worth trying.

     The PRESIDENT explained that there were not sufficient craft in the Mediterranean to permit of detailing vessels to guard convoys while they were being passed through the gates of such a barrier.

     The Conference then recommended as follows:-

          “The Conference was not prepared to recommend the establishment of a mine barrage between Sicily and Cape Bon in view of the difficulty of passing the large amount of traffic through such a barrage without very large gateways, which would render the barrage ineffective.

          The representatives of the United States and Japan did not, however, concur in this opinion, and the former considered that this barrage should be established with constricted gateways.”

     The question of priority of the various barrages was now discussed.

     REAR-ADMIRAL RATYE said he would like to bring to the notice of the Conference the proposal of the Allied Commander-in-Chief for the protection of the route Taranto-Itea-Salonica, by closing the Gulf of Patras and the Gulf of Athens. He considered this should be done with material available after the Ægean barrage was completed.

     REAR-ADMIRAL STRAUSS thought that the barrage in the Gulf of Patras was a question for local decision. He objected to putting 20 miles of mines to protect a 70 mile passage.

     The PRESIDENT proposed that the order of priority should be--

          1. Dardanelles.

          2. Otranto Barrage.

          3. The Barrage agreed to in the Ægean.

     REAR-ADMIRAL STRAUSS asked if the question of priority could not be confined to Otranto and Ægean, as otherwise America would become involved in the Dardanelles scheme, in which she had no part.

     The following priority as regards the establishment of mine barrages was finally decided:-

          1. Dardanelles. This however, did not refer to the                  lines of mines between Imbros and Cape Gremea,                  which may possibly be laid late if material is                 available.

          2. Adriatic.

          3. Ægean.

          4. Protection of the entrance to the Eubœa Channel.

          5. Protection of the entrance to the Gulf of Patras.

     The latter should only be considered after the minefields and barrages in the Ægean had been completed.

     The Conference then dissolved.

ALLIED CONFERENCE ON MEDITERRANEAN MINELAYING

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APPENDIX I.

CAPTAIN LITCHFIELD-SPEER -- NOTES ON MINUTE 2 of AGENDA.

(a) Deep Minefields.

     May be used as whole or part of a barrage or at selected points on traffic routes. It is accepted as a policy that such fields must be skimmed by a searching sweep before traffic of first class importance is allowed to pass over them.

     A deep minefield cannot be effective alone. It must be effectively patrolled day and night and at night it should be illuminated either permanently or intermittently. Alternatively, some means of causing submarines to dive such as surface obstruction, is required.

     In other words, a deep minefield is only effective when a submarine dives into it. A submarine will only dive when there is some good reason for it. They prefer to proceed on the surface or at periscope depth.

     Deep minefields are useful in positions where submarines are likely to lay on the bottom.

     The limitations and disadvantages of a deep minefield are:-

       (i.) It requires constant and dense patrol, the number of vessels being proportioned to the length of the field and the distance from a base.

        (ii.) It is less effective at night, even if illuminated, and is probably not effective at all in thick or bad weather.

       (iii.) Submarines can pass over it with impunity unless made to dive into it.

     On the other hand, there are the following advantages:-

       (i.) An area so mined can be made safe for the passage of surface ships over it.

       (ii.) Compared to other forms of under-water obstructions, such as nets and mines, a deep minefield is simple, less dependent on a base in the proximity, less dependent on fine weather for laying and maintaining, and probably in the long run less expensive.

       (iii.) The lavish use of simple material, e.g., single mines at different depths, is a sound axiom in mining and generally preferable to any system of connected mines, nets, or combination of nets and mines.

       (iv.) The use of deep minefields by the British has given good results and several submarines are known to have been destroyed in them.

     This is especially the case in the Dover deep mine barrage, but this is rather a special case as the waters are narrow.

     There is no doubt, however, that submarines do still pass the barrage on the surface or at periscope depth at night or in thick weather. Possibly some pass through by passing through the barrage close along the bottom or at other depths and are lucky.

     The minefield is, however, being constantly reinforced and portions of it are being laid shallow. Owing, however, to the strong tides and great rise and fall of tide a mine barrage effective to the surface cannot be made in this locality by the simple expedient of laying moored mines close below the surface.

     Taking the above remarks into consideration, the conclusions and recommendations:-

       (i.) Deep minefields should only be used as an anti-submarine barrage where free passage of surface vessels over it, is necessary or desired.

       (ii.) Narrow waters with a base close at hand for the patrols are best suited for deep minefields.

       (iii.) A special application is on traffic routes in spots specially favoured by submarines, such as off headlands or where routes converge, where an attacking submarine is likely to be driven down by an escort.

       (iv.) The requirements of an effective anti-submarine mine barrage are:-

          (a) It shall be effective day and night from the lowest depth, to which submarines will dive in attempting to pass it, to the surface.

          (b) It shall be reinforceable.

     (v.) The disadvantages of a complete anti-submarine barrage to surface is that it requires gates for passage of friends and neutrals. Freedom of movement of surface traffic is therefore restricted.

     In regard to (iv.) (a) :-

     (i.) The governing principles are correctly stated in greater detail in U.S. Memorandum No. 168, and these were accepted by the Allied Naval Council at the meeting held in London on 23rd July, 1918.

     (ii.) The greatest depth to which submarines will willingly dive is at present generally accepted as 300 feet, but up to the present no British mines have been laid at a greater depth than 185 feet, American 240 feet.

     When laying mines at great depths it is necessary to take into consideration the effect of the pressure at that depth.

     As regards British mines, present types suitable for use in a barrage were designed as regards strength of material, to withstand pressure at a depth of 440 feet, say 70 fathoms, but allowing for material below standard this figure may be put at about 240 feet (40 fathoms).

     Selected mines may be taken as good for 300 feet. In the case of the British mine there is also another consideration-there is a limit to the depth at which mines can be moored without the pressure overcoming the buoyancy and rendering the safety gear operative, thus putting the mine out of action. These depths are :-

              H 2 mine       (By 410 lbs).       240 feet.

              H 2  "         ( " 550  " ).       392  "

     (iii.) Given that a mine barrage is potentially effective from the surface to the bottom or greatest depth required the degree of its effectiveness is measured by the probability.

     The probability depends primarily on the number of mines per mile at any particular level.

     The probability factor of a minefield shows the chance a submarine has in passing through a field without actuating a mine.

     Example—40 miles per mile. Submarine, 20 ft. beam.

          Normal approach. No tide. Probability 19%.

     This means that of every 100 submarines passing on the surface, or at any particular level, 19 should fire mines.

     Probability in a horizontal plane is governed by the horizontal spacing. This is limited in any one line by counter-mining distance--say 150 feet. 40 per mile. Probability on a vertical plane is governed by the vertical spacings, i.e., difference in level of tiers of mines.

     In the case of contact mines the difference in depth of tiers of deep mines should not exceed the overall height of a submarine--say 25 to 30 feet.

     Probability at any level can be increased in proportion to the number of lines of similarly spaced mines at the same level.

     Probability is also affected by :-

       (a) Minefield efficiency (effect of rise of tide and dip due to tide) especially in the case of the upper tier laid against surface passage.

       (b) Tide athwart the line of mines and by submarine approaching at an angle.

   In both cases the effect is to increase it.

     By the use of non-contact mines, i.e., mines fitted with some device by which the mine is fired by means other than by actual contact with the mine itself, an increase in Mean Probability for a given number of mines can be obtained at the expense of a corresponding reduction in Explosive Efficiency     Both Probability and Explosive Efficiency should be taken into consideration when planning any mine barrage, so that we have some definite idea of what results are to be expected and if the objective in view will be achieved.

     Nothing short of a stone wall, however, can be regarded as an absolute anti-submarine barrage. There are perhaps advantages in not aiming at too high a degree of efficiency, at any rate in not expecting it.

     A constant toll at a reasonable percentage should be satisfactory and it may be argued that this is better than bottling by a too effective barrage.

     Moral effect should not be lost sight of. A few mines may act as a deterrent

     (iv.) Mine barrages may be laid with mines which take their depth automatically or with fixed moorings cut or adjusted to the required length. The latter necessitates accurate placing in accurately surveyed positions.

     It is recommended, however, that mines should be laid automatically whenever possible. There is practically no alternative in the case of the upper layer of a barrage to the surface. Automatic deep laying has only recently become practicable. Formerly fixed moorings had to be used for the deeper layers.

REINFORCEMENT.

     This has been mentioned. It is a point needing consideration in the planning of a mine barrage, selection of material and choice of position.

     The durability of the upper tier of a mine barrage cannot be expected to be great. It depends on depth of the mines, weather and tides; principally on weather for depths--say 30 feet. Below that depth a high degree of durability may be expected but gaps may be opened due to various causes, submarines, spontaneous explosions, fish wreckage.

     In order to ensure the safety of the minelayers the position of the mines laid must be accurately known and there must therefore be some means of fixing it. Marking the positions by buoys is undesirable, except temporarily.

     In tideless waters Dead Reckoning from a shore fix where land is not in sight makes fairly close reinforcement practicable. Each case must be taken on its merits. There are systems of mining which provide for close reinforcement, but they are either not suitable in their present state of development for use in deep waters or not likely to be available in sufficient quantities.

(b) Mine-net Barrages.

     Tactically mine-net barrages and deep minefields are similar.

     A mine-net barrage does not fulfil the requirements put forward for an effective anti-submarine barrage. It requires to be closely patrolled or supported by surface obstruction; otherwise submarines will not dive into it.

     If brought up to the surface endurance will certainly be very low, it is visible and submarines can and do pass over it at night or in thick weather. Unless it extends to at least 300 feet below the surface submarines can and will pass under it when they know it is there.

     Theoretically it is an attractive proposition, because for the area it covers it present 100% efficiency as an obstruction, but not necessarily anything approaching this figure for destruction.

     Mines of small charge are necessarily used on account of consideration of handling in small vessels and facility for attaching to the nets.

     The probability of destruction or disablement is increased by the number of mines and their distribution in the nets.

     Certain destruction requires the mine to be in contact when it fires.

     Fine weather is necessary for laying and maintenance. Rate of laying is limited by weather as well as by supply of materials.

     Proximity to a base is necessary.

     Results with fixed mine-net barrages in British waters have been disappointing and not in proportion to the energy and material expended. They are less used than formerly.

     The British net-mine is an E.C. mine with 45 lb. charge, increased in new design to 65 lbs.

     Cases are known of submarines fouling the mine-nets and getting clear without firing the mines, also in which the mines fired and the submarine got home.

     The mine-net barrage at Dover was certainly not effective. Submarines passed over it and under it. The locality is, however, unfavourable owing to the strong tides.

     In tideless waters a mine-net barrage has a better chance and if supported well below the surface as in Otranto Barrage. This, however, leaves a free passage over it. In its present form submarines can also pass under it with ease if they find out details of it. In its favour is the agreeable fact that a large submarine has been destroyed in it during the last few days. This is very satisfactory but not necessarily conclusive.

          Also in its favour are the facts that it has :-

          (i.)  Proved a practical proposition in laying.

          (ii.) Proved effective in at least one case already to           which may be added some moral effect.

          (iii.) Material is in sight and completion before                mines suitable for the locality can be provided is               practically certain.

          (iv.) Can be more easily made safe than a mine barrage           if desired. It may be regarded as semi-controlled.

ON THE GENERAL QUESTION RAISED IN MINUTE 2.

     The use of mine barrages is recommended in preference to the use of mine-net barrages for general application, but it is necessary to make some reservations in the case of the Mediterranean.

       (i.) There are certain technical difficulties to be overcome in the laying of mines in soundings greater than     200 fathoms and at depths below the surface as great as 300     feet. Existing designs are not suitable for this and,    though improvisation may be possible, it is usually not    satisfactory.

       (ii.) Practicability of the proposition depends largely        upon the tidal data.

          Up to 300 fathoms if tide is not in excess of ½-knot from surface to bottom it should be practicable.

          Also in currents of greater strength if it does not extend below say 50 fathoms with still water below that.

          Moorings of greater length than 300 fathoms are not considered feasible except in still water.

          Currents in the Mediterranean are stated to be surface.

          It is necessary to define that and to ascertain to what depth their strength is experienced.

       (iii.) A high buoyancy mine is necessary to support the weight of the great length of mooring rope.

            Probable minimum size is 94 wire

            Weight in water 104 lbs. per 100 fathoms

            For an effective charge this means an increase in size of mine beyond those now in use. This may entail alteration to minelayers as well as other disadvantages.

          The United States Technical Officers are understood to be looking into the problem, but they will certainly require exact information in regard to currents and depths.

          If mines are used the use of American mines and minelayers is recommended for the following reasons : -

(a) The American mine is specially suitable for anti-submarine mine barrages for which purpose it was designed.

(b) Great Britain will be unable to produce the mines in the numbers required, or to spare the minelayers and at the same time meet requirements in home waters.

          British mines are suitable and are recommended for any surface fields required in waters of normal depth such as off the Dardanelles, or by small deep minefields on trade routes in selected positions.

          In view of the uncertainty that must remain for the present as to whether mining in great depths is practicable, the use of mine-net barrages should be considered as an alternative, having proved to be a practicable proposition at Otranto.

          The difficulty will be :-

          (i.)  Number of vessels required for effective patrol.

          (ii.) Bases.

          (iii.)Provision of vessels and material

          (iv.) Personnel for laying.

          These require consideration.

          In the meantime the completion of the present mine-net barrage at Otranto is recommended and also of the proposed second line which should extend to a depth of 300 feet if practicable.

          In order that the barrage shall be effective at night some form of surface obstruction or means of making submarines dive is essential and should be provided. Towed de Quillac mines may meet the requirement. Alternatively, illumination by flares or searchlights.

 

ALLIED CONFERENCE ON MEDITERRANEAN MINELAYING

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APPENDIX II.

LIST OF DELEGATES COMPRISING the SUB-COMMITTEES

____________________

(A) To discuss the question of the Dardanelles Minefields:-

          Captain E. R. Morant (Great Britain).

          Captain de Fregate, E.F.M.H., Magescas (France)

____________________

(B) To discuss the question of offensive measures as regards Mining in the Straits of Otranto and between Cape Bon and Sicily:-

          Captain F. S. Litchfield-Speer (Great Britain).

          Captaine de Vaisseau, J.E.H., Frochot (France).

          Capitano di Corvetta F. Ruspoli, R.I.N. (Italy).

          Tenente di Vascello A. Lais, R.I.N. (Italy).

          Commander K. Kishii, I.J.N. (Japan).

          Commander C. R. Train, U.S.N. (United States).

____________________

(C) To discuss the question of establish Minefields in the Ægean:-

          Captain R. M. Burmester, Commodore, 2nd Class (Great Britan).

          Captaine de Corvette, E.L.H. Dubois (France).

Capitano di Corvetta R. de Bellegrade de Saint-Lary, R.I.N. (Italy).

          Lieutenant N. Davis, U.S.N. (United States).

ALLIED CONFERENCE OF MEDITERRANEAN MINELAYING

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APPENDIX III.

REPORT OF SUB-COMMITTEE ON THE DARDANELLES MINEFIELDS.

______

MEMBERS:-

CAPTAIN E. R. MORANT (Great Britain).

  CAPITAINE DE FREGATE MAGESCAS (France).

______

(A)Present situation as regards Minefields off Dardanelles.

     Since June 1st, 1918, 1,280 mine have been laid off the Dardanelles.

     It is considered that practically all the deep mines laid in 1917 are still in existence, i.e., 1,029, and perhaps 600 to 700 of the original 12 feet mines are still remaining.

(B) Arrangements already made for extending and reinforcing off Dardanelles.

       (i.) The completion of the double line between Tenedos and Imbros.

       (ii.) The laying of a double line, 12 feet deep, between Cape Suvla and Kephalo.

       (iii.) The continuation of filling the gap between Tenedos and the mainland, and laying mines off Gallipoli shore by motor launches.  

       (iv.) In the event of the local authorities considering that the Ponente Niger line should be reinforced forthwith another 700 mines would be required. These should not be taken from the Mudros reserve.

     2.   The completion of this programme entails the expenditure of 1,370 mines, making in all 2,650 mines in the new field. The probable existing number of mines off the Dardanelles will be about 4,000, of which 1,029 are deep. This does not include the 700 mentioned in B (iv.) above.

     3.   There at present:-

                             575 H Mines at Mudros

                             250 Briguet mines at Mudros

                             500 Briguet mines at Malta

                             ---

              Total  . . . 1,325

     This number is not sufficient to complete the programme by 40.

     4.   It is moreover necessary to have a reserve of 1,500 mines at Mudros to reinforce the whole field after winter gales. This reserve should always be kept up.

          Malta could be used as a mine depot to enable this to be done. It is not certain what the capacity of Mudros is as to storing mines--a mine park is being made now.

          There are about 500 mines now on their way out, which should be sent straight to Mudros.

(C)      When mines can be laid in 200 to 400 fathoms are available, a field should be laid between Imbros and Cape Gremea against surface ships and submarines.

ALLIED CONFERENCE OF MEDITERRANEAN MINELAYING

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APPENDIX IV.

REPORT OF SUB-COMMITTEE ON ÆGEAN MINING.

MEMBERS.

COMMODORE R.M. BURMESTER. (Great Britain).

CAPITAINE DE CORVETTE E.L.H. DUBOIS. (France).

CAPITANO DE CORVETTA R. DE BELLEGARDE DE ST. LARY. (Italy).

LIEUTENANT N. DAVIS. (UNITED STATES).

__________________________

I.

     1.   COMMODORE BURMESTER said that the sub-committee had to discuss the proposal to establish in the Ægean anti-submarine minefields or barrages. Having decided the principles which should govern a barrage and its location, there was another proposal which had been brought up by Admiral Ratyé and which they would have to consider, namely the protection of a fleet base at the Northern entrance to the Eubœan Channel, also a barrage at the Southern entrance. There was also a third proposal which the President of the Conference wished the sub-committee to consider and that was the protection of the traffic route at the Western entrance of the Gulf of Patras. The question of the possibility of establishing a barrage in the Gibraltar Straits was also referred for some further consideration by this sub-committee.

     2.   He then proposed that they should proceed to consider the main question of anti-submarine barriers in the Ægean and asked Liuetenant Davis, U.S.N. to explain the proposals of the United States for mining in this area.

     3.   LIEUTENANT DAVIS proposed that they should proceed, using as their guide the conclusions arrived at and agreed upon by the Allied Naval Council as to the requirements of an anti-submarine barrage. This was accepted by the members of the sub-committee, who then proceeded to discuss informally the best positions for such barrages.

     4.   Lieutenant Davis explained the lines of mines proposed in United States Memo. No 168; their advantages and disadvantages.

     5.   COMMODORE BURMESTER pointed out with reference to the line most favoured by the representative of the United States that it had the serious strategical disadvantage of including in the area free to enemy submarines operating from Constantinople our most important bases in the Ægean, i.e. Mudros and Salonica, and suggested that a mine barrier between Akti Peninsula, Thaso, Samothraki, Imbros, Tenedos and the Mainland would have the very considerable advantages of continuing enemy submarines within a smaller area and would also require much fewer deep mines, as the major portion of it would be in depths of less than 100 fathoms.

     6.   LIEUTENANT DAVIS called attention to the fact that such a line would not prevent Smyrna being used as a submarine base and also appeared to be in practice too close to the enemy’s coast and therefore difficult, if not impossible, to safeguard against enemy sweeping. The right flank of such a line would also be in enemy territory at a position difficult for us to control.

     7.   CAPITAINE DE CORVETTE DUBOIS and CAPITANO DI CORVETTA BELLEGARDE considered the line proposed by the United States as the most satisfactory.

II.

     1.   The following general conclusions are submitted by the sub-committee.

     2.   It is considered that it is desirable that there should be a complete anti-submarine barrage in the Ægean Sea to comply, as far as possible, with the principles laid down by the Allied Naval Council.

     3.   It is considered that the mine barrage, No. 4 of the barrages in the Ægean, in Memo. No. 168 of the United States of America is the most suitable that can be suggested by the sub-committee.

     4.   It is considered that there should be one gate only in the deepest water of the Doro Channel. If, subsequently, other gates are found necessary they can be easily arranged for.

     5.   The gate should be not less than 500 nor more than 1,000 yards in width and should be free for passage of vessels on the surface only. It will require to be guarded by day and night to prevent the passage of submarines on the surface.

     6.   Two tugs and six trawlers will be required to control the traffic, to pass sailing ships through and to reinforce escorts in the immediate vicinity of the gate in the Doro Channel. For the Channels between Andros, Tinos, Mykoni, Nikaria, Themina, Furni and Samos, seven vessels would require to be constantly patrolling, involving a total requirement of twelve vessels.

     7.   For the mine barrier between Samos Island and Cape Kanapitza two watching vessels will be required, i.e. a total of three.

     8.   It will be necessary to maintain a sufficient armed force at Samos to prevent the enemy obtaining control of both sides of this Channel.

     9.   It is considered that the responsibility for the provision, laying and maintenance of the minefield should be entirely in the hands of the United States and that the method of laying and details of plans should be left to the Government responsible for executing the project.

     10.  The question of which nation will provide the two tugs and twenty-one trawlers, which were estimated as necessary for the patrol of the barrage, is reserved for decision by the Conference, depending upon the requirements of similar vessels for the other barrages.

     11.  It appears desirable that the authority responsible for establishing and maintaining the mine barrage should have the patrol vessels placed under his general orders.

     12.  It is considered that the allocation of the responsibility for the provision of the land forces indicated as necessary for the defence of Samos should be reserved for the consideration of the main conference.

     13.  It is observed that the barrage as proposed will seriously restrict the movements of naval forces, and it is suggested that this point should be further considered by the main conference.

     14.  It is observed that if this project is put into execution the coastal and inter-island shipping will be largely interfered with, that this is a matter which principally affects the Government of Greece, and that this question should therefore be taken up with that country at the earliest moment possible in order that their concurrence and co-operation may be obtained.

     15.  It is suggested that a passage for small craft, such as caiques, would be possible in the Eastern Ægean in the Furni-Boghaz, which has a width of less than 100 yards and could be closed by a net.

     16.  It is considered that the establishment of a separate base in the Ægean for this project will not be necessary, but that use should be made of the main base established in connection with the other mine barrage proposals under consideration.

     17.  A note on the tides and currents in the Ægean as they affect the above proposals is attached as an Appendix.

III.

     1.   CAPITAINE DE CORVETTE DUBOIS submitted the following proposals made by the Commander-in-Chief, Allied Fleets, with reference to a double barrage North and South of the Eubœan Channel. The two advantages of these barrages would be firstly, to safeguard the supplying of the Army at Salonica through the Eubœan Channel, and secondly to allow the Allied Fleet the use of the Gulf of Volo as an exercising ground. In this connection also it was desired, for strategical reasons, to have a base for the Fleet at a greater distance from the Dardanelles than Mudros. These barrages would consist of a heavy net laid in the Trikiri Channel. To complete these two barrages the Commander-in-Chief, Allied Fleets,13 suggests laying a mined net defence at the entrance of the Gulf of Athens to prevent enemy submarines laying mines there, and to avoid the necessity of much sweeping. For the same reason a similar fixed barrage with mines is suggested by the Allied Commander-in-Chief, to be placed at the entrance to the Gulf of Petali between Petali Island and the coast of Greece.

     2.   COMMODORE BURMESTER said that the expense of establishing and maintaining a mine net barrage for a considerable distance, such as that suggested between Petali Island and the Mainland, did not appear to be justified solely in order to ensure the protection of what must always be a relatively small number of ships.

     3.   It is considered by the majority of the sub-committee, that simple form of heavy net, provided with a gate, between Cavaliani Island and the Mainland would be adequate, under the circumstances, for the protection of the Southern portion of the Eubœan Channel.

     4.   For the protection of the Northern entrance to the Eubœan Channel, it is suggested that a barrier should be placed between Cape Griva and the nearest point of the Island of Eubœa. This barrier to consist of heavy anti-submarine nets, provided with a gate, and this should be supplemented by a moored mine net. It is understood that Great Britain is the only country which can at present supply and lay this heavy net, and it is therefore suggested that this nation should do so, making provision also for the Southern entrance to the Eubœan Channel. The mine net should also be supplied by Great Britain and laid by France. It is considered that the question of the supply of gate vessels, patrols, and sweepers for the net should be reserved for the consideration of the Allied Commander-in-Chief.

     5.   The provision of mine or net barrages in the entrance of the Gulf of Petali and the Gulf of Athens are not at present considered essential in view of the proposed establishment of the large schemes of barrage, and in view of the expenditure of material and personnel involved, compared to the extent of the traffic to be protected.

IV.

     The sub-committee next considered the question of establishing barriers at the entrance to the Gulf of Patras, that is between Cape Dukato and Cape Vlioti in Cephalonia, and between Cape Scala and Cape Glarenza. It was observed that this would entail a mine or net barrage of about 20 miles in length which would provide protection mainly for ships on passage to and from Patras, and Gulf of Corinth, and the Ægean via the Corinth Canal, and that it would in fact only protect these ships for a distance of about 70 miles of their voyage. It was, therefore, suggested that although this would appear to be a useful measure it should not be executed until supplies and material for other and more important schemes are assured. It is suggested that the most satisfactory method of establishing this barrage would be by means of a complete anti-submarine minefield between Cape Glarenza and Cape Scala and by a moored mine net between Cape Vlioti and Cape Dukato, the latter patrolled by surface vessels towing de Quillac mines. It is proposed that the necessary mines should be provided and laid by the United States and that the fixed mine net should be provided by Great Britain and laid by France. It is proposed that the concrete blocks and mooring buoys of the mined net between Cape Dukato and Cephalonia should be provided and manufactured under the same conditions as those which are now being supplied for the Otranto--Fano fixed barrage. It is presumed that France will provide the necessary vessels for patrolling the nets and watching the minefield.

V.

     With reference to the establishment of a mine barrage in the vicinity of the Gibraltar Straits, this has not been examined in detail in view of the remarks of the main conference, but the sub-committee observed that the combined tidal stream and current in the Straits is noted as attaining at times as much as five to six knots. The establishment of a moored mine barrage under those circumstances, and in view of the great depth of water that obtains, appears impracticable.

 

APPENDIX TO REPORT BY SUB-COMMITTEE ON ÆGEAN MINING.

Currents and Tides in the Ægean.

________________________

General.

     Currents are irregular in strength and direction, run generally to the southward, and are greatly influenced by winds, especially in the western part.

     As a general rule currents are strong during and after North-easterly winds than with those from the Southern quarter.

     The level of the water in the Ægean is more influenced by winds than by tides. At Khalkis Bridge spring tide rises about 2 feet.

     It is probable that accurate current observations have never been undertaken, and certainly those remarks that are made only apply to the surface currents. It is probable that in almost every case there is a lower counter current running in the opposite, e.g. in Doro Channel and Samos Straits. Careful Observation would be necessary to determine this.

     Generally the southerly set in the channels of the Cyclades is accounted for partly by the continual flow of water from the Dardanelles.

Doro Channel.

     Generally a southerly current of about 1¼ knots, but increasing to 3 knots at times, and occasionally more.

Mykoni Channel.

     Current dependent on wind, generally from northward.

Steno Pass.

     South-westerly current, dependent on wind.

     Between Nikaria and Mykoni currents probably generally to the southward.

Furni Pass.    (Between Nikaria and Samos).

     Current sets to the northward, causing at times a confused disagreeable sea.

Samos Strait.

     Current generally to the eastward, sometimes attaining a speed of 3 to 4 knots.

 

ALLIED CONFERENCE OF MEDITERRANEAN MINELAYING

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APPENDIX V.

REPORT OF SUB-COMMITTEE ON ANTI-SUBMARINE BARRAGES IN THE OTRANTO STRAITS AND CAPE BON-SICILY CHANNEL.

_________

MEMBERS.

CAPTAIN F. S. LITCHFIELD-SPEER (Great Britain).

CAPTAINE DE VAISSEAU J. E. H. FROCHOT (France).

CAPITANO DI CORVETTA F. RUSPOLI (Italy).

COMMANDER K. KISHII (Japan).

COMMANDER C. R. TRAIN (United States).

TENENTI DI VASCELLO A. LAIS (Italy).

I. Otranto Straits.

     An effective anti-submarine barrage across the Southern Adriatic is considered essential and to be of primary importance as it deals with the principal enemy submarine bases.

     The Sub-Committee first considered the proposal of the United States for a mine barrage in the Straits of Otranto as set forth by the United States’ Delegate to the Sub-Committee as follows, due consideration being given to the fact that the United States is ready to lay mines of existing design in 500 fathoms :-

(a)  That any mine barrage project should entail no mixed authority or responsibility.

(b)  That a barrage must be a complete barrier, that is, a barrage from the surface to diving depth of submarines.

(c)  That no barrage would be acceptable that required a large patrol for its efficacy.

(d)  That no halfway barrage would be acceptable, that is, a patrol mine barrage to reinforce a net, etc.

(e)  That as far as practicable gates should be limited to one.

     The Italian and French delegates were insistent that they could not decide on the principle of a barrage permanently dangerous for the passage of vessels on the surface owing to its restrictions to the free movement of their fighting forces, and they judged it necessary to refer as regards this to their respective Commanders-in-Chief. Lacking instructions on this point they preferred to rely on an extension of the present mine net barrage, i.e. completion of the present one and the laying of a second one, which will extend to a depth of at least 300 feet from the surface, and to deal with the passage of submarines over the net by means of patrols by day and towed de Quillac mines by night.

     They also represented that the present net barrage should be made effective at greater depth by laying mines below it (not immediately below but in the vicinity) as soon as possible in depths up to 500 fathoms and later right across.

     French and Italian delegates also recommended laying a deep minefield flanking the net barrage.

     The efficiency of a net mine barrage, though extended and improved as regards surface passage at night as an effective barrage was discussed. It was generally agreed that its limitations were :-

(a)  The large number of vessels required for effective patrol.

          (b)  Ineffective in think weather, especially by day.

          (c)  Ineffective in bad weather.

          (d)  At night the obstruction is a travelling one.

          (e)  In only a less degree dangerous to patrols and                   vessels in chase or retiring.

     In regard to the above :-

          (a)  Patrols are stated to be adequate.

          (b)  Thick weather is rare in the locality.

          (c)  With notice, surface can be made safe by signal.

     The limitations of a net mine barrage have been indicated above. It is necessary also to consider a complete mine barrage in the same way. Its disadvantages are :-

(a)  It restricts free movement on the surface and necessitates gates.

(b)  It is liable to damage and loss of efficiency as a surface obstruction in bad weather.

          (c)  It is perhaps less safe to reinforce closely.

     On the other hand, it is believed to be, when complete, the most effective barrier to the passage of submarines on the surface or submerged.

     It was generally agreed that the American system of a complete mine barrage from 300 feet to the surface, effective at all times under all conditions, had most in its favour, and assuming that it could be maintained, it was the one which best fulfilled the fundamental principles which had been accepted by the Allied Naval Council.

     It is, however, a question first for the Italian and French Commanders-in-Chief to say if they will accept the limitations imposed by a complete mine barrage to the surface, with one or more gates in it, preferably one. The British Commander-in-Chief, in view of the British forces operating in the southern Adriatic is also concerned in this question.

     If the limitations as regards freedom of movement can be accepted, a line Otranto-Cape Linguetta, with slight deflection to the southward of the Cape, is recommended. It is better strategically than the direct line Otranto-Saseno because it permits free exit for forces at Valona to the Northward. Subject to confirmation by sounding, the depth does not exceed 500 fathoms, and should be suitable for laying the mines offered by the United States.

     The United States Delegate14 stated that the present American mines could be arranged for laying in 500 fathoms and he understood at a depth of 300 feet and that the endurance of the upper tier would be satisfactory. The practicability of mooring mines in such great depths depended, however, on definite data in regard to the strength of the current and the depth to which its effect extended.

     A gate five miles wide is suggested on this Otranto-Linguetta line, the western end of it about nine miles from Otranto. Gate to be marked with buoys, say about two miles north and south of the gate. This gate is in deep water unfavourable for German mines. It should be mined with deep mines. Gate to be narrowed if possible after experience. This line and gate position interferes least with freedom of movement north and south and between the east and west shores of the Southern Adriatic.

     This proposal is recommended for consideration. It is a first mining measure supplementary to the net barrage.

     Owing to the possibility of the Italian and French Commanders-in-Chief not agreeing to a surface barrage, which would, in any way, hamper movements of their forces, the Sub-Committee recommend a line Cape Santa Maria de Leuca--Fano Island for alternative consideration. It appears from the chart that the soundings here are not much greater than on the Otranto--Cape Linguetta line. If this is confirmed by examination and mining is possible there, this line has the following advantages:-

(i.)  It is much less open to the objection of hampering Allied forces.

          (ii.) Less open to attacks by enemy sweeping.

     On the other hand, there may be heavier seas there than further north, and the gate must be further from the land and the distance of patrols from a harbour considerably greater.

     The Sub-Committee recognise the value of the Otranto--Fano Island line, but as that line requires delay for development of the 600 fathom mine, it cannot be regarded as an immediate proposition for a complete barrage, though it would appear possible to lay a considerable portion, if not all of it, flanking the net barrage where the depth does not exceed 500 fathoms. This is desired by French and Italian delegates but does not meet the conditions under which the American offer is made.

     If a complete mine barrage effective to the surface is ruled out for these waters owing to objections raised by the French and Italian Commanders-in-Chief, reliance must be place on the net mine barrage which it is recommended should be completed in any case. If a complete mine barrage is not laid, a second net mine barrage should be laid with nets to 300 feet below the surface and the question of raising it closer to the surface should be considered.

     It is pointed out that unless the patrol is effective and the principle of towing de Quillac mines at night as a surface barrage is accepted, this barrage will not seriously affect the submarine situation.

     The Sub-Committee consider it necessary to represent these essentially vital conditions most strongly, otherwise submarines will undoubtedly continue to pass over the barrage at night and by day also in thick weather. It is a necessary condition of this system that all traffic over the barrage at night should be stopped unless special arrangements have been made for safe passage.

     To summarise, our recommendations are :-

(i)  Subject to acceptance of surface obstruction by Commanders-in-Chief concerned, to lay a complete mine barrage on either

          (a) Otranto--Cape Linguetta line

or   (b) Cape Santa Maria de Leuca--Fano Island line with a gate of agreed width in deep water at the western end. This gate to be protected by deep laid mines patrolled by day and at night closed by towed de Quillac mines.

(ii.)  To complete present net barrage, and, at any rate pending completion of a mine barrage effective to the surface, to make provision for :-

          (a) Strong and effective patrol by day.

          (b) Effective obstruction to surface passage of                      submarines at night by towed de Quillac mines in                 sufficient quantity.

          (c) Passage over barrage at night to be stopped.

(iii).    If a complete mine barrage, as in (i) effective to the surface, is not laid, a second mine net barrage should be laid, as has been proposed by Italy and France, but with the net deepened to 300 feet and raised closer to the surface if possible.

          The same conditions (a), (b), and (c) as for (ii) are essential.

(iv.)     As there may possibly be some unexpected delay or unforeseen difficult in completing an effective mine barrage in such great depths, it is considered necessary to proceed with the preparation of all the material for the second mine net barrage.

(v).      Also in the event of (i) not being accepted, France and Italy desire that a deep mine barrage should be laid flanking the present net to supplement the net and stop the passage of submarines under it.

(vi.)     In the event of (i) being favourably entertained, it is recommended that immediate action be taken to obtain definite data in regard to soundings, surface and sub-surface currents on the lines of the proposed mine barrages.

II.  Cape Bon-Sicily.

     1.   The necessity for an anti-submarine mine barrage Cape Bon-Sicily depends primarily on the establishment of :-

              (i.)  An efficient barrage across the Adriatic ;

(ii.) An effective barrage barring enemy bases in the Ægean ;

(iii.)An effective barrage in the North Sea and English Channel.

     If barrages (i.) and (ii.) were complete and reasonably effective now, the establishment of Cape Bon-Sicily barrage would not be recommended in view of its necessarily affecting freedom of traffic. The Sub-Committee appreciate that this latter is a matter for very serious consideration. The question of thick weather and protection of fishing industry requires special consideration.

     There is also the question of possible resultant concentration of enemy submarine activity in the Eastern Mediterranean.

     The Sub-Committee are impressed with the fact that some considerable time must elapse before effective barrages at Otranto and in the Ægean can be completed and therefore free intercommunication of enemy submarines between Western and Eastern Mediterranean is possible. They consider it important to stop this and in view of the fact that material suitable for the Cape Bon-Sicily barrage is offered by the United States and is practically ready for shipment, they recommend the establishment of this barrage on the understanding that the material used will make an effective barrage from the surface to 300 feet below it. Elia mines are mentioned in a United States telegram.15 It is desired to observe that experience of the British with Elia mines is not very satisfactory.

     A deep minefield only in this position would not suffice, because it is not considered that it could be patrolled effectively and it does accord with accepted principles for a complete barrage. The maintenance of this barrage, after completion of effective barrages at Otranto and in the Ægean, may not be necessary. Any inconvenience or disadvantages may then outweigh its advantages under present conditions.

     2.   The Sub-Committee have had the advantage of consulting Commodore Baird, Director of Shipping Movements, Mediterranean, in regard to the passage of convoys through a barrage between Cape Bon and Sicily.

     The requirements stated by Commodore Baird are :-

(a)  A gate half-a-mile wide at each end for local

     coasting traffic.

          (b)  Two gates, each five miles wide, for convoys.

(c)  Gates for convoys preferred in the shallow water

     area between the 100 fathoms line and Sicily.  

     Experience is that submarines avoid this area.

     They frequently operate in areas south and west  

    of Pantellaria.

(d)  Passage of barrage at night as well as by day is

     essential for convoys.

(e)  Line of barrage well inside the north-west limit

     of the shoal waters is preferred.

     The Sub-Committee recognise the necessity for giving due consideration to expert opinion on these points, and generally it concurs in and recommends the above requirements, but they feel it necessary to point that a total width of opening of 11 miles proposed for gates will seriously reduce the effectiveness of the barrage. They recommend that this be more seriously examined with a view to reducing the width of the gates and possibly adopting only one gate for the convoys. The United States Delegate strongly urged this point. The Sub-Committee also doubt the advisability of putting the gates in the shoal waters.

     It is proposed that the gates for coastal traffic should be close in to the shore at the African and Sicilian ends and that no traffic through the barrage be permitted at night except by convoys or war vessels of the Allies when necessary.

     It is proposed that the gates be protected by deep laid mines, say 60 feet deep for highest tier, and that those gates should be patrolled by day and covered against surface passage of submarines at night by towed de Quillac mines. The use of de Quillac mines and the necessary craft for service on barrage must not be at the expense of the efficiency of the Otranto barrage.

     Arrangements to be made that time of convoy passing the Barrage is signalled to Officer in charge so that safe passage of the gates can be arranged for. The question of obstructing the Straits of Messina was considered. This offers a possible though difficult alternative route for enemy submarines.

     In view of the depth of water and strong tides in the Straits, it is not considered that an effective mine barrage is practicable. This probably applies to nets also.

     There is insufficient data before the Sub-Committee regarding the strength of the tide at various depths to enable a definite opinion to be given on the practicability of mine or net barrages at some other point in the vicinity of the Straits, e.g., entrance to Gulf of Gioja or between Taormina--Cape d’Armi.

     The Sub-Committee consider it necessary that some means should be provided for detecting and preventing the passage of enemy submarines through the Messina Straits.

     The Sub-Committee also urge the necessity for obtaining definite data in regard to depths and currents on the line of the proposed Cape Bon--Sicily Barrage and in and near the Straits of Messina assuming that the Cape Bon--Sicily project will be proceeded with.

III.  Other Minefields in the Adriatic.

     The Sub-Committee do not recommend any other minefields as anti-submarines measures in the Adriatic.

 

APPENDIX No. 1 TO REPORT OF SUB-COMMITTEE ON ADRIATIC

AND CAPE BON--SICILY BARRAGES.

__________________

REMARKS  BY  COMMODORE  G.  H.  BAIRD.

(Director of Shipping Movements, Mediterranean).

__________________

     I view with some apprehension the laying of a barrage in the Strait between Cape Bon and Sicily under the conditions in which it is proposed to lay it.

     The situation in the Mediterranean, at present, is roughly this. There are in the Adriatic some 30 enemy submarines. During the last three months only two enemy submarines are known to have come from the west ; one other sunk on the way. Therefore practically all submarines operating in the Western Mediterranean have come from the Adriatic.

     Now, if you close the passage between Cape Bon and Sicily without at the same more effectively closing the Straits of Otranto than at present, it will mean a concentration of the Adriatic submarines in the Eastern Mediterranean.

     There are two remarks I have heard during the various discussions which cause me some uneasiness. One was that the mines were ready and should be laid. It does not seem to me a wise policy because a certain weapon is ready that it must be used. In this case, if the mines are laid in the Straits between Cape Bon and Sicily, I am not at all sure that they are being used to the best advantage.

     The second remark was that the traffic both in troops and stores were considerably increasing in the Western Mediterranean and in fact that in the east was only two-thirds of that in the west. This remark alone appears to me to intend a protection to the Western Mediterranean at the expense of the Eastern Mediterranean.

     Can we afford a concentration of submarines in the Eastern Mediterranean ? Are the extra escorts available ? Are the hunting flotillas ?

     The time is coming when the Homeward Eastern convoys are going to be extremely valuable, and also of increasing size. They must come from Port Said and either go through the Malta Channel or south of Malta, both narrow waters, and to the eastward of the proposed barrage. Again, a large amount of grain for Italy comes from Port Said and is diverted into Syracuse ; the average monthly amount is 110,000 tons. This diversion with concentration off Syracuse will be more dangerous than ever.

     It is all very well for us to sit down and put a barrage on a paper chart, but when it comes to the practical navigation through that barrage it becomes a very difficult problem.

     The navigation of convoys in bad weather has, in my experience out here, proved most inaccurate. That the case of “Matiana” going on to the Keith Reef.16 Many other cases might be quoted.

     I have asked, in the event of the barrage being approved, for gates of at least 5 miles, and even now I am not quite sure that this width is enough.

     The result of this barrage will eventually be that convoys will not pass through at night owing to the danger and fear of not hitting off the gate. Possibly they will not have been able to take good observations. Neither will they go through in the day-time in bad weather when sights are not to be relied on.

     They will therefore be slowed down, or their zig-zags increased, and thus their danger will be greatly added to, as they will be a longer time in a dangerous zone.

     In my opinion the increased risks to submarines are in no way counterbalanced by the added dangers to navigation.

     I consider the mines composing this mine barrage could at present be more usefully employed elsewhere.

     To sum up, this barrage, if laid before the Otranto Barrage becomes more effective, will simply mean adding an extremely dangerous zone to merchant shipping in the centre of the stream line of the world’s commerce, from east to west and vice versa.

     It is a well-known fact that the weak link in the chain of stream line convoys is the Mediterranean, owing to inadequate escorts, the ideal conditions for submarine attack, and it is my opinion that if you place a danger to navigation across that stream line and so allow of a concentration of enemy submarines in the Eastern Mediterranean, you will be practically break that link.

APPENDIX NO. 2 TO REPORT ON SUBCOMMITTEE ON ADRIATIC

AND CAPE BON--SICILY BARRAGES.

___________________

     Current observations take by the late Commander R.L. Hancock, and extracts from “Sailing Directions” are attached. Commander Hancock’s observations show the current to be small at the entrance to the Adriatic but to extend to a considerable depth, though of feeble strength.

     Officers with experience of the present Otranto Barrage have observed stronger currents, but say that no difficulty has been experienced on account of currents in that locality, the effect of which is not appreciable on the moorings of the buoys.

     In the other localities the experience of officers with local knowledge of the positions under consideration is that the current is rarely so strong as given in “Sailing Directions.” Generally the currents are very variable in strength, much affected by winds and believed not to extend far beneath the surface.

     It is important that definite data of surface and sub-surface currents at positions selected for mining should be obtained. If possible a practical trial to determine the effect is desirable.

_______________

CURRENT OBSERVATIONS IN ENTRANCE TO THE ADRIATIC,

MADE BY THE LATE

COMMANDER R. L. HANCOCK

Latitude   …   …	39° 50’ 00” N.	39° 48’ 35” N.	39° 48’ 10” N.	39° 47’ 55” N.
Longitude  …   …	19° 17’ 45” E.	18° 41’ 15” E.	18° 32’ 40” E.	18° 24’ 30” E.
Wind  …    …   …	South 1-2	North 1-2	North 2	North 2
Depth in fathoms	568	92	65½	56
Nature of Bottom	gy. cl.	gy. m. s.	gy. m. s.	m. s. sh.

 

Depth Fms.)	Mean direction	Velocity (knots)	Mean direction	Velocity (knots)	Mean direction	Velocity (knots)	Mean direction	Velocity (knots)	Mean direction	Velocity (knots)
5	SE	.28	NbE	.24	NNW	.10	NW	.46	WSW	.34
10	SEbE	.20	NNE	.40	NW	.18	WNW	·44	WSW	.40
20	EbS	.34	NE	.20	NWbW	.40	NWbN	.33	__	__
30	EbS	.35	EbN	.06	NW	.46	West	.15	__	__
40	East	.29	NEbE	.15	SEbS	·37	__	__	__	__
50	EbS	.26	East	.13	SE	·45	SSW	.13	__	__
60	__	__	NE	.07	South	·18	__	__	__	__
70	__	__	SSE	.33	__	__	__	__	__	__
80	__	__	SEbS	.37	__	__	__	__	__	__
100	East	.13	__	__	__	__	__	__	__	__
150	ENE	.10	__	__	__	__	__	__	__	__
250	__	__	__	__	__	__	__	__	__	__
350	North	.20	__	__	__	__	__	__	__	__

 

 

NOTES FROM SAILING DIRECTIONS ON MEDITERRANEAN CURRENTS,

____________________

Otranto Straits.

     South of Cape Otranto the inshore current follows the trend of the coast to the southward ; as a rule this is weak but with northerly winds may attain three knots. The winter months are the worst. During the summer there are usually fresh westerly winds during the day and the current sets constantly out of the middle of the straits.

     On the Albanian coast the current sets to the north westward following the trend of the coast.

Gulf of Xeros.

     The currents in the Gulf of Xeros are irregular and appear to be influenced by the wind ; after a fresh northerly wind for a few hours, a strong southerly set has been experienced, but directly the wind moderated the current ran strongly in the opposite direction. In the bight of the coast off Enos, northward of Cape Gremea, the currents are strong (two or three knots an hour) and irregular.

     The current in the vicinity of the Zurafa Rock has been observed to set eastward two knots an hour.

Cape Bon-Sicily

     In the channel between the coast of Tunis and Sicily, the current, under ordinary circumstances, and especially in fine weather, sets to the eastward (especially near Cape Bon and across the entrance of the Gulf of Tunis), at a rate of from half a knot to one knot. In the middle of the channel, near Skerki Bank and Keith Reef its direction is more variable, and, with westerly winds it has been known to attain a velocity of four knots. In the vicinity of Cape Bon, after a succession of winds from north and north-west the direction of the current is often to the southward and south-south-westward. In this channel with a south-east gale it has been found setting E.N.E., nearly two knots an hour, and at Keith Reef with a north-west wind S.E. by E., three miles an hour ; but on other occasions the current has been known to set N.N.W. in this locality. H.M.S. “Thunderer,” during a moderate north-west gale in the month of February, 1881, found the current setting S.W. by S. between Pantellaria and Cape Bon at the rate of one mile an hour.

|fn12:This request from Sims has not been found.