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Admiral Henry T. Mayo, Commander-in-Chief, Atlantic Fleet, to Secretary of the Navy Josephus Daniels

Carlton Hotel,

London, England.

8 September 1917

From:     Commander in Chief, Atlantic Fleet.

To  :     Secretary of the Navy (OPERATIONS)

SUBJECT:  Report of International Naval Conference held in London. 4-5 September 1917; and kindred matters.

References:(a.)  C-in-C. despatch 04005 September 1917 to OpNav.

           (b.)  C-in-C. dispatch 09006 September 1917 to Opnav.

Enclosures:    A – List of officers present at Conference.

          B – Summarized agenda paper for Conference.

          C – Copy of Reference (a).

          D – Copy of Reference (b)

     1.   References (a) and (b) contain the gist of the Conference proceedings. In order to indicate the entire sequence of events connected with the Conference, this report will begin by relating matters which took place before the Conference are being written up and will be available later.

     2.   Upon arrival at Liverpool on Monday 27 August, Rear Admiral de Chair presented an autograph note from Admiral Jellicoe, First Sea Lord, in which inquiry was made as to the agenda paper for the Conference.1 Upon arrival in London Admiral Jellicoe very soon brought up this matter as he was desirous of informing the governments concerned in order that their representatives might be instructed in the premises. It finally became advisable to give the First Sea Lord the following memorandum in writing :-

          The purpose of the present visit of the

     Commander in Chief of the United States Atlantic

     Fleet is, in general terms, as follows:-

          (1)  To learn more fully what has happened and what has been done.

          (2)  To get more closely in touch with what is being done.

and then

          (3)  To discuss what it is proposed to do.

          The above outline is indicated in order that the United States, first having full information as to past and present plans, may then more clearly appreciate proposals looking to future operations, all to the end that the United States may more intelligently and effectually employ its strength and resources in co-operation with the Allies to win the war.”

     3.   The First Sea Lord then on Tuesday 28 August sent the following message to the British Naval Attaches in Paris, Rome, and Petrograd-2

          “Most secret from First Sea Lord.

          Following subjects for discussion at Naval Conference:

          (1)  Question of offensive operations against enemy’s   fleet or bases.

          (2)  Manner in which United States Navy can best co-     operate with Allies for successful prosecution of war.

          (3)  Measures necessary to deal with enemy’s submarine      cruisers of large radius of action.

          (4)  Measures necessary for the establishment of      convoy system in all waters frequented by enemy submarines     and provision of necessary vessels.

          (5)  Offensive measures against enemy submarines.      Inform Minister of Marine accordingly.”3

     4.   Upon suggestion from the Navy Department contained in OpNav dispatch 19029 August Japan was, on Friday 31 August, asked by the British Admiralty to have a representative present at the Conference and, further, it was proposed to call in a Portuguese representative should matters affecting Portugal come up.4

     5.   The conference met at 11 A.M. Tuesday 4 September 1917 in a Board Room of the Admiralty Building. The Conference was presided over by Sir Eric Geddes, the First Lord of the Admiralty, the senior official representatives present being:-

          Great Britain

               Sir Eric Geddes, First Lord of the Admiralty.

               Admiral Sir John Jellicoe, First Sea Lord.


               Vice-Admiral du Bon, Chief of Naval Staff.5


Rear Admiral Cusani-Visconti, Deputy Chief6of Staff.


               Rear Admiral Funakoshi 7


               Rear Admiral Kedroff 8

          United States

               Admiral Mayo

               Vice Admiral Sims.

     N.B. – Full list of officers present attached in Enclosure “A”.9

     6.   Sir Eric Geddes, First Lord of the Admiralty, on behalf of the British Government, having offered a welcome to the representatives of the navies of the powers united against Germany, reminded them that the Conference was called at the suggestion of the United States Government and called upon the Commander in Chief of the United States Atlantic Fleet, who then stated that he had come with no definite instructions but with the desire to learn how the United States Navy could best assist and co-operate with the Allied navies, particularly in dealing with the submarine menace which the United States Government regarded as especially serious at the present time; he also emphasized his conviction of the value of personal intercourse between officers of the United States and the Allies navies.

     7.   The original agenda paper contained eight items which was later expanded to ten items; all of which appear in Enclosure “B”.10 The Conference, after agreeing to expansion of the number of items of the agenda at the instance of any nation represented, proceeded with the agenda.

     Item 1. The Question of a Close Offensive in German Waters.

     8. (a) The First Sea Lord stated in general terms that an offensive operation against German bases in the Helgoland Bight had been for some time under consideration by the British Admiralty, and said that it was essential to know, before going further, whether the powers represented would wish to have proposed in detail a scheme which would involve the sinking of approximately the following allotments of old warships, as merchant vessels could not be spared for the purpose:-

                         Battleships         Cruisers

          British - - - - -   18                13

          French  - - - - -   5                12

          Italian - - - - -   3                 3

          Japanese- - - - -   2                 7

          Russian - - - - -   -                 -

          United States - -   12                 8

                              40                43

     (b)  It was further stated that the operation in mind was a very difficult one and that he would not go into details at this time. The primary object was to block submarines in by blocking up the German exits  into the North Sea, no other object  being worth the risk involved. It was repeated that further development of such a scheme was wholly dependent upon the willingness of the governments concerned to furnish the vessels indicated, which were to be loaded with concrete before sinking and were to be supplemented in the shallower parts by hulks and barges either made of concrete or partly filled with concrete.

     (c)  The United States representative was unable to state the views of his Government. The French representative thought it might be possible. The Russian representative made a plea for a vigorous offensive in order to relieve the pressure now being put upon Russia by the enemy. The Japanese representative thought his Government might be willing. The Italian representative demurred as he thought his Government considered that the Italian ships mentioned were of very great use in their present employment.

     (d)  The Conference, after discussion, agreed that the question should be carefully considered by the government concerned and that they should indicate in due course to the British Admiralty the contribution of old warships which they would be prepared to furnish, should the contemplated operation appear practicable after due consideration of all the difficulties involved.

     Item 2.   The Alternative of a Mine or Net Barrage Either                     in German Waters or Further Afield.

     9.   (a)  The British Admiralty put forward as an alternative to a close offensive in German waters, the suggestion that the activity of enemy submarines might be restricted by the laying of an effective mine field or mine-net barrage. If such an operation were undertaken it appeared that it would take the form of:

               (1)  An efficient mine-field barrage so as to      completely shut in the North Sea, which was estimated to      require about 100,000 mines, a number which would not be      available for some considerable time, or

               (2)  A barrage of mine-nets for the same purpose   which proposal was, in view of experience to date, deemed         impracticable.

     (b)  It was stated further that while about 50,000 mines had already been laid in the Helgoland Bight, neutral waters were still accessible to and used by enemy submarines and that British submarines were constantly on watch at such neutral exits as well as occasional destroyer patrols. The difficulties of fixing position had gradually required the laying of new mines to be done further out from Helgoland until a considerable area in that part of the North Sea was dangerous for friend as well as foe.

     (c) As to the proposal to put down a mine barrage in the northern part of the North Sea, while it could be guarded against enemy sweepers, certain difficulties exist such as lack of freedom of movement of the Grand Fleet, so that a very promising degree of success should be indicated before such an undertaking was begun.

     (d) The Conference, after discussion, agreed that the distant mine barrage could not well be undertaken until an adequate supply of mines of satisfactory type was assured and that, until or unless such conditions ensue, the improvement and extension of the present system of mine fields was desirable, and further, that a barrage of mine-nets was impracticable.

     (e) The British shortage of skilled personnel especially fitters (mechanics) required for the assemblage of mines now under construction being brought up, it was agreed that the government represented should be asked to consider what assistance they could render in this respect.

     Item 3.   Offensive Measures Against Enemy Submarines in                     the North Sea.

10. (a) The British Navy was stated to be strained to such an extent in guarding and in assisting to guard overseas communications that actual offensive against submarines in the North Sea was largely done by such units of the Grand Fleet as could be spared for the purpose. There was related the development of “hunting groups” which relied chiefly upon the hydrophone or kite-balloon, or both to locate enemy submarines, and that seaplanes were very useful for this purpose and were being allocated to this duty as rapidly as the many other urgent calls on the air service would permit. It was also stated that there was under construction a special type of submarine for work against enemy submarines, armed specially with a large number of small torpedoes with a view to discharging a “salvo” of them at an enemy submarine which is a very difficult target for a single torpedo.11 So far a the data indicates that submarine vs submarine is most successful, then “Mystery ships” though the latter are not now so effective as formerly due to increasing wariness of the enemy, then the destroyer and patrol boats of various kinds, the chief value of the latter appearing to be that they cause enemy submarines to dive at once in order to avoid them.

     (b) After discussion, the Conference agreed that the most desirable anti-submarine measures were:-

               (1) To attack or block enemy submarine bases,

               (2) To mine the submarines in effectively,

               (3) To attack the submarines at sea –

And it was felt that these measures should be amplified, expanded and improved as rapidly as the availability of vessels and material enabled the one or the other or any of them to be followed up.

     Item 4.   Measures to Deal With Enemy Submarine Cruisers of Large Radius of Action on the High Seas.

     11.  (a) As six enemy submarine cruisers (so-called “Deutschland” type) are expected to be ready for sea before the end of October, consideration must be given now to measures necessary to be initiated very soon in readiness to deal with  this matter. A striking need is for additional long-distance radio service in arc area not now covered by existing allied radio stations, but the said area can lately be covered by the establishment of long-distance radio service in the Azores.

          (b) The British Admiralty put forward for consideration the following measures:-

               (1) Use of decoy ships, working in concert with submarines, which will accompany them.

               (2) Concerted measures for preventing the establishment of enemy submarine bases overseas.

               (3) Convoy of all craft, including friendly neutrals as far as possible.

               (4) Development of a radio warning system and of an intelligence centre in the Azores.

          (c) After discussion of the several measures proposed in sub-paragraph 10 (b) above, it was agreed that (1) thereof ought to be a useful measure; and that (3), in view of reported armament of 6 inch guns for cruising submarines of the “Deutschland” type, would require larger and more powerful escort vessels than some now employed, and that it might even become necessary to use battleships on escort duty, therefore that the governments represented should consider whether they could provide the class of vessels deemed desirable for escort duty. It was further agreed to refer measures (2) and (4) to a committee composed of two British, two French, one United States officers, that the Portugese Naval Attache, (Captain Lieutenant Carvalho) should be invited to join the committee and that the report of the committee should be adopted as embodying the views of the Conference in the premises.12

          (d) The committee report stated that they agreed:-

               “(1) That the respective Admiralties and Ministries of Marine should communicate with their Colonial Ministers and ask for instructions to be given to their Colonies and overseas posessions to keep supervision over all harbors and anchorages to gain intelligence of German submarines or suspicious vessels.

               (2) That steps be taken to ensure close co-operation between Allied Ministers in neutral countries to make such representations as will ensure adequate steps being taken to prevent submarines or suspicious vessels being succored or allowed to make use of territorial waters.

               (3) That the following steps be taken as regards the Azores, the Portuguese Government being first asked permission:-

                    (i) United States Naval force to be based in the Azores.

                    (ii) A British Intelligence center to be established.

                    (iii) British directional radio station to be established.

                    (iv) British long-distance radio station to be established for the war.

                    British units to work under the general directions of the United States senior naval officer.

     The French representative brought up the question of the difficulty of receiving radio intelligence   from vessels attacked by submarines in the South Atlantic and, more particularly, off the coast of South America.

          It was also agreed that the question of fitting certain ships in convoys with powerful radio installations to relay messages should receive consideration whenever convoys should be established.”

     12. An additional point touched upon (during discussion of item 4) was the possibility of the Germans sending a battle-cruiser accompanied by a high-speed supply vessel, to operate in the Atlantic, not only for the purpose of raiding convoys but also with a view of drawing the British battle-cruisers in pursuit. No formal opinion was recorded as varying views were expressed as to the likelihood of such an operation being attempted, but it was deemed apparent that such a move would be very difficult to deal with and that the use of battleships as escorting vessels for the convoys was indicated.

     Item 5.   Establishment of Convoys Universally for Outward and Homeward Trade and Organization Necessary.

13.       (a) The First Sea Lord made a statement at length of the general arrangements for convoys in the Atlantic, inviting attention to the improvements that had been made and were making as well as to relative loss of tonnage due to delays incurred by waiting for convoys to assemble, and that all of the experience to date indicates the necessity for more frequent convoys, which will require more escorting ships and, in view of expected increase in size and effectiveness of enemy submarines, heavier ships while the need for more destroyers and small escorting vessels of that general type is not yet adequate for the convoys in operation. Difficulties are expected with outward bound convoys which will usually be in ballast and therefore more or less unmanageable at close quarters, this being particularly true of the “tramp” type.

          (b) It was further pointed out that convoy system in Atlantic has so far given good results but that lack of sufficient and suitable escort vessels had been the cause of considerable losses of shipping in the Scandinavian trade which has to cross the North Sea, and also that the shipping losses in the Mediterranean showed a greater percentage of loss than in any other area, although an Allied naval council now sitting at Malta was making arrangements for the establishment for a more satisfactory convoy system in the Mediterranean.

          (c) Among other things the British Admiralty held the view that the following numbers of small escorting vessels were considered the minimum desirable:-

     (1)  Convoy of 20 ships and over – 10 to 12 escorting vessels

     (2)         12            -  6   8      

     (3)         about 8 ships   -  4             

          (d) It was agreed that the above views of the British Admiralty were concurred in and that the governments represented had additional cause to give careful and early consideration to the furnishing of additional cruisers and other escort vessels.

          (e) The French representative suggested that the United States seriously consider whether some of their older battleships could not be sent to the Eastern Mediterranean thus releasing the French battleships now stationed there so that the French Naval personnel thus made available could be used to man French cruisers not now sufficiently manned for sea service and these cruisers then employed in the extension and improvement of the convoy system.

     Item 6.   Establishment of Convoy System in Mediterranean. Necessity for This System in Order to Ensure Adequate Supply of Coal to Italy and to Economic Tonnage.

14.       (a) The British Admiralty invited especial attention to the shipping situation in the Mediterranean where the percentage of loss was greater than in the Atlantic and was becoming a matter of increasing embarrassment. The present lack of an adequate convoy system was not only causing large actual losses in shipping but also large virtual losses because of the delays incident to the coasting routes so generally used and also to the routing of certain shipping via the Cape of Good Hope instead of via the Suez Canal.

          (b) After discussion it was agreed to refer this question to a committee composed of two British, two French, one Italian and one Japanes e representative, the Senior United States representatives having requested that the United States representatives be excused from assignment to the committee in view of the fact that the United States is not at war with Austrial.

          (c) The report of the committee was duly presented and was approved and adopted by the Conference for further reference to the consideration of the Allied Council now in session at Malta on the general question of transportation in the Mediterranean.

     Item 7.   The Laying of the Otranto Barrage and its Defense by Allied Destroyers. Aircraft and Submarine Patrol for the Barrage.

15.       (a)  The British Admiralty stated that the laying of the fixed barrage in the Straits of Otranto will shortly be begun but that its completion would take some time during which the view was held that the drifter barrage now being maintained should no longer be allowed to go on inadequately protected as the losses due to enemy raiders were quite large and interception or even destruction of raiding vessels after attack on the relatively small and lightly armed drifters could not be considered an adequate protection.

          (b)  It was further stated that a protective force composed of at least 6 destroyers maintained on patrol duty at night was necessary. Of this number Great Britain prepared to provide the number of destroyers required (probably 5 or 6) to maintain 3 on patrol and asked that the Italian naval authorities should provide the number necessary to maintain the other 3.

          (c) The Italian representative, after saying that his Government considered patrol by destroyers dangerous as they and the French have already lost one each in the Adriatic, and that they preferred to endeavor to intercept the enemy raiders, finally agreed to present the views and request of the British Admiralty to his Government and to see if they would furnish the necessary vessels.

          (d)  The French representative stated that the French Ministry of Marine would have no objection to some of the French destroyers already allotted to Italy being used for this work in conjunction with Italian destroyers.

          (e) The matter of submarine and aircraft patrol for warning against enemy raiders as well as for anti-submarine work was also discussed and agreed upon as useful during daylight but that their employment must be supplemented by the proposed destroyer patrol at night.

     Item 8.   Offensive Measures in the Adriatic Against Enemy Bases.

16.  (a) The Italian representative was invited to give the views of the Italian Government as to the possibilities of offensive operations against the Austrian Naval forces in the Adriatic. . .

     Item 9.   Assistance by Allied Fleet in the Protection of Archangel Route and White Sea from Submarine Attack.

17.       (a)  This matter was considered by the Conference at the request of the Russian representative, who urged the importance of the immediate provision of protective forces for Kola Bay similar to those now maintained outside of Archangel, or that at least when Archangel became closed on account of ice the protective forces should not be withdrawn as was done last year but rather transferred to protect Kola Bay. He anticipated that German submarines would be kept later this year on routes to Russian White Sea ports because Russia had just completed a new naval and mercantile harbor at Kola Bay open all the year round and connected with Petrograd by a new railway line. He finally asked whether Great Britain could not supply at least 12 armed trawlers for this purpose.

          (b) The First Sea Lord, replying to the above, and while expressing the desire of Great Britain to render their several Allies all assistance in their power, stated that owing to the shortage in the number of armed trawlers available there could be no definite hope offered that the request could be complied with, that last year the armed trawlers were withdrawn during the winter months for repairs and because German submarines had ceased to operate in far northern waters. He also stated that the British Admiralty did not anticipate that German Submarines would operate later this year as the Russian representative indicated but that British armed trawlers would remain north as long as German submarines did operate and that consideration would be given to what could be done to meet the request made by the Russian representative.

     Item 10.  Assistance to Italy by the United States of America in the Direction of Supplying Material.

18.       (a) This matter was requested for discussion by the Conference at the instance of the Italian representative who had before him a list of material already ordered and wished to emphasize difficulty which had been experienced due to delays in delivery.

          (b) The Senior United States representative undertook to make representations in the premises to his Government concerning the material mentioned as already ordered but suggested that any further material assistance desired should be taken up through the usual channels.

19. Arising out of comment made during the discussion of Item 10 above, the question of provision of United States destroyers or additional British destroyers for service in the Mediterranean came up, and the First Sea Lord stated that if the destroyer programme of the United States resulted in the relied of British destroyers from some of the duties in which they are now engaged, additional British destroyers would no doubt be sent to the Mediterranean for anti-submarine work or for trade protection.

Kindred Matters Growing Out of Conference.

     20. During the day the Italian representative asked the United States representative (out of conference) whether in view of the United States destroyer programme, Italy might hope to purchase some destroyers from the United States, which proposal the United States representative agreed to refer to his Government, as was done in Reference (b).

     21. The French representative called on the United States representative at the latter’s hotel to express the anxiety of the French Government in regard to the transportation, landing and supply of American troops for service in France and renewed his Government’s request that this matter be made the subject of an early conference. The United States representative agreed to present the matter to the Navy Department, as was done in reference (b).

     22. The Conference completed its sittings at about 6:30 P.M. 5 September. The fact is that, while the Conference was very useful to all concerned, it is extremely difficult to reach any conclusions other than those of a very general nature, as representatives usually lack authority to make definite arrangements and usually have been furnished with instructions to press matters which affect their own countries particularly, which tends to restrict their appreciation of the broad scope of the Matters usually dealt with in conferences.

                                   (Sgd.) H. T. MAYO

Source Note: Cy, DNA, RG 45, Entry 517B. Two attachments include a comprehensive list of attendees and a list of agenda items.

Footnote 1: RAdm. Dudley R. S. de Chair, and First Sea Lord Adm. Sir John R. Jellicoe.

Footnote 2: Captain Fitzmaurice Acton, British Naval Attaché at Paris, Captain Dennis A.H. Larking, British Naval Attaché at Rome, and Commander Harold G. Grenfell, British Naval Attaché at St. Petersburg.

Footnote 3: Charles Chaumet.

Footnote 4: This dispatch has not been found.

Footnote 5: VAdm. Ferdinand de Bon.

Footnote 6: RAdm. Marchese Cusani-Visconti.

Footnote 7: RAdm. Kajishiro Funakoshi.

Footnote 8: RAdm. Mikhail Kedroff.

Footnote 9: For a copy of this enclosure. see, DNA, RG 45, Entry 517B.

Footnote 10: For a copy of this enclosure. see, DNA, RG 45, Entry 517B.

Footnote 11: British R-Class submarines.

Footnote 12: Cmdr. Fernando Branco, Portuguese Naval Attache at London.