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Commodore William A. Howard Kelly, Commander, British Adriatic Force, General Instructions and Scheme of Operations for Otranto Barrage Force



15th April, 1918.


     The following General Instructions and Scheme of Operations for the Otranto Barrage Force are promulgated for the information and guidance of the officers concerned.

     2. These orders are supplied to commissioned officers only. Skippers are supplied with an abridged edition containing only Sections (A) and (H) and Paragraphs 6 to 20 of Section (l). Divisional Leaders are responsible that Commanding Officers of all vessels of their division thoroughly understand the orders which concern them and know how to carry them out. Commanding Officers are to make themselves fully conversant with the orders supplied to them, and should impartas much of them to the officers and men of their vessels as is necessary for them to perform their various duties.

     3. These orders are tobe kept in the weighted guard book which will be supplied, and they are to be treated in every respect as a Confidential Book.

     4. In addition to these standing orders, a series of Barrage Force Confidential General Memoranda of a permanent nature and a series of Confidential Temporary Memoranda will be issued from time to time by the Captain of the Barrage to those concerned.


Commodore Commanding              

British Adriatic Force.      

(This Memorandum has been distributed as shown on back).




     1. The duty of the Barrage force is to search for, attack and destroy any enemy submarines entering or leaving the Adriatic. The successful execution of this duty is of paramount importance to the country, and the success expected can be achieved only by the most conscientious efforts of every officer and man, both afloat and ashore. Owing to the nature of the operations, success or failure may depend on any individual officer or man, and it is only by the most perfect “team work” and a complete understanding and execution of orders given that the enemy can be defeated.

     2. It cannot be too much emphasized that the destruction of enemy submarines will only be achieved by the unselfish work of all concerned. When a submarine is destroyed or captured, it is hoped that all officers and men employed, whether on the sea, beneath the surface, in the air or on land, will realize that the credit belongs, not merely to those who dealt the last blow, but is shared by all whose conscientious and hard work has rendered the delivery of the blow possible.


     1. It is proposed to so dispose the submarine surface and air forces of the barrage that any enemy submarine wishing to pass in or out of the Adriatic will be forced to avoid attack by gunfire or bombs by diving for a considerable distance, greater than the normal capacity of the submarine.

     2. While travelling submerged through the barrage area, the submarine’s presence will be detected by hydrophone vessles, by hydrophones or other instruments laid out from shore, or by aircraft and kite balloons. On being detected, the submarine will be pursued by hydrophone vessels, attacked by depth charges, bombs or paravanes and either destroyed or forced to come to the surface, there to be attacked and sunk by gun fire.

     3. Even if the vessels hunting the submarine with hydrophones are not able to make a successful depth attack by depth charges on account of the submarine zigzagging, this zig-zagging will reduce the available capacity of her electric motors and will force her to come to the surface earlier than would otherwise be the case, or may result in her turning back and not undertaking the passage of the barrage.

     4. It is probanle [i.e., probable] that, as soon as the increased barrage force is assembled and at work, the submarines will endeavour to pass the Straits.during the night on the surface, trusting to their speed and invisibility.

These tactics it is hoped to counter by the proper employment of flares, with which all vessels of the barrage will be supplied, and which illuminate a large area around the vessel firing them, also by the employment of star shells.

     5. The absolute necessity for the following cannot be too strongly impressed on every officer and man:-

(a) A thorough understanding of the methods laid down to be employed.

(b) The strict compliance with all signals and orders given, so that several vessels may co-operate without interfering with each other.

(c) A most conscientious hydrophone watch being kept at the times laid down.

(d) A good look-out on deck being kept at all times.


1. Submarines. Submarines, although not forming part of the barrage proper, will:-

(a) Endeavour to attack any enemt submarine or surface craft approaching the barrage.

(b) Give information to the barrage force of any enemy submarines or surface craft.

     (c) By their presence beyond the limits of the barrage, force enemy submarines to dive in order to avoid being attacked or reported, thus forcing them to expend their battery power.

2. Destroyers. The part played by the destroyers of the barrage force will be as follows:-

(a) The advanced force will:-

    (i). Cause enemy submarines to dive in their area.

    (ii). Give warning of the approach of any enemy destroyers or cruisers, and will attack and shadow them while reporting their movements.

    (iii) Discover, by the employment of hydrophones, the presence of enemy submarines, and endeavour to sink them or drive them into the barrage

  (b) Destroyers, other than the advance force, will act as supports to the trawlers, drifters and motor launches, co-operating with them in using their hydrophones, and on the submarine coming to the surface, will pursue it and sink it by gunfire.

3. Trawlers and Drifters. These will be disposed in such a manner that enemy submarines passing through the barrahe [i.e., barrage] will have to pass within the normal hearing range of two or more such vessels, when their presence should become known and reported. The vessels fitted with Fish hydrophone or other sensitive detecting instruments will then take over the hunt; the remaining vessels co-operating and endeavouring to encircle the submarine so that the latter must pass through within attacking distance of their depth charges.

     4. Sloops fitted with Kite Balloons and Hydrophones. These ships, so fitted, with their long range of vision, will force the submarine to dive at a long distance off, or, alternatively, if she comes in sight, will hunt her by means of observations from the kite balloon or by the employment of hydrophones, and will at once call on the nearest available hunting unit to assist in the hunt.

5 AIRCRAFT. Aircraft will:-

  (a) Patrol by day and on moonlight nights the area not covered by the surface craft, and will report and attack by bombs any submarine sighted.

  (b) Patrol large areas to the southward of the barrage, and thus either force the submarine to dive or make its presence known.

  (c) Be ready to come out immediately on the call of any of the barrage craft sighting a submarine and will (i) if on the surface, attack by bomb, or (ii), if submerged, assist in the hunt.

  The many other duties which are carried out by aircraft, such as reprisals on enemt bases and reconnaissance, are not connected with the Barrage Orders.

  6. Motor Launches. Motor Launches will keep hydrophone watch on the flanks of the barrage and will at all times be ready to answer a call from the barrage to proceed at full speed to the position from which the submarine is reported, whether by hydrophone and ‘K”’ tube stations, barrage vessels or aircraft.

  7. Light Cruisers. British and Allied Light cruisers and Allied destroyers are held at instant readiness to proceed out and attack the enemy forces.

  8. “K” Tube, Hydrophone and Look-out Stations. These stations will conform to the instructions issued from time to time by the Commodore Commanding. They will pass information of any vessels sighted or heard, other than those known to belong to the barrage force working in the areas assigned to them. The necessary information as to the disposition of the barrahe craft and the times of silent intervals for hydrophone listening will be communicated to the stations. The position and course of any suspicious vessel heard or sighted should be given if possible.

  “K” tube and hydrophone stations should also be able to hear when mines are laid, and, by carefully plotting the submarine’s course, the exact position of each mine should be noted. It should also be possible, by carefully following the silent intervals, to obtain the relative position of submarine and hunting vessels, and to transmit to the latter the bearing and distance of the submarine from them.


  1. The northern limit of the barrage is latitude 41.14 north. To the south there is no limit, except that for the present French submarines are operating in the area bounded by the following:-

  Latitude 39.52 North       Longitude 18.22 East) See D.P.

           39.26   "                   18.22  "  ) Form No.19

           39.17   "                   19.14  "  ) Dated 21st

           39.07   "                   19.14  "  ) January 1918.


  1. The Commodore Commanding British Adriatic Force, is in general command of the whole Barrage force.

  2. The Senior Officer of destroyers, will be in immediate command of the advanced force of these vessels placed to the north of the barrage.

  3. The Captain Commanding Otranto Barrage Force, or his representative, will command all other vessels of the Barrage Force, and, under orders received from the Commodore commanding, will also control all traffic passing through the Barrage area. Should the Captain of the Barrage find it necessary to call on the Senior Officer of destroyers to re-inforce the supporting craft on the barrage, he may ask for his assistance, which should be rendered if possible.

  4. The Senior Officers of the Barrage Force are:-

                         ) ***  (Captain Gilbert O.Stephenson,

Captain Commanding       ) ***  (R.N., H.M.S. “Whitby Abbey.”

Otranto Barrage Force    ) ***  (Short title – Captain (B).

                           ***  (Commander Charles E.Turle,R.N.

Second in Command        ) ***  (H.M.S. “Hussar.” Short Title –

   of Barrage Force      ) ***  (Commander (B).

                         ) ***  (Lieutenant Commander John P.

Third in command         ) ***  (Farquharson,R.N.,H.M.Y. “Paulina”

    of Barrage Force     ) ***  (Short title –Lieut.Commander (B).

  5. In the absence of Captain (B) either Commander (B) or in the latter’s absence, Lieutenant Commander (B) will assume command of the Barrage Forces as his representative, conforming to the general instructions issued by Captain (B). This is not however to restrict their freedom of action should necessity arise. Either Commander (B) or Lieut. Commander (B), should always be on the Barrage, and the dates of coaling etc. of the vessels in which these officers are accommodated should be arraged accordingly. All movements on the barrage will be ordered by Captain (B), or his representative.

  6. The special nature of the methods employed in the detection and hunting of enemy submarines controlling the action of other units in the immediate vicinity, irrespective of the seniority of the Officers Commanding. Under these circumstances, it is confidently anticipated that officers will loyally co-operate with one another, keeping in mind that our one objective is the successful destruction of enemy submarines.


  1. Commander (B), Commander (B) will be responsible for the general supervision of all Trawlers and Drifters. He will arrange for the refits, coaling etc. of all trawler and drifter divisions, and submit the programme to the Captain (B) a fortnight in advance if possible, in order that the projected movements may be promulgated as necessary. He will deal direct with the Commanding Officer of H.M.S. “Queen” and another depot and repair ships concerning work required to be done on those vessels, in order that they may be able to perform the duties required of them. He will also deal direct with the Commanding Officers of Depot Ships on all questions concerning the personnel of trawlers and drifters, except with regard to questions arising out of orders issued by Captain (B) or concerning Commissioned Officers which should be referred to Captain (B) before action.

  2. Lieutenant-Commander (B). Lieutenant-Commander (B) will be responsible for the general supervision of all Motor Launches attached to the Barrage force; he will arrange the dates of their refits, relief, etc., and will submit a programme of the projected movements to Captain (B) a fortnight in advance if possible, so that they can be promulgated. He will arrange direct with the Senior Naval Officer, Gallipoli, regarding all questions of repairs, personnel etc., except with regard to questions arising out of orders issued by Captain (B), or of Commissioned Officers, which should be referred to Captain (B), before action.


  1. Disciplinary offences on the Barrage will be dealt with by the Senior Officer of the division. Any infringement of orders issued by Captain (B), should be reported to Commander (B) by trawlers and drifters, and to Lieut.Commander (B), by Motor Launches, and these officers will report all offences of a serious nature to Captain (B).

  2. All other disciplinary offences should be referred when necessary to the Commanding Officer, H.M.S. “Queen”, or to the Senior Naval Officers at Corfu or Gallipoli.


  The general line of action to be taken by the Barrage forces on being attacked by enemy surface craft is as follows:-

  (i). On receipt of the information of the approach of enemy surface craft, all vessels except destroyers move to the south at full speed without closing in on one another, in order to give the enemy the greatest distance to go before he can make an attack and, by employing a smoke screen, force him to approach very close to any vessel before attack by gun-fire is practicable, thereby increasing the chances of Allied forces coming into action with the enemy.

  (ii). A smoke screen may be made by the vessels of the northern line, this action to be determined by the weather and other conditions at the time. If weather conditions are favourable for making a smoke screen, every vessel should be prepared to make one if so ordered, taking into consideration the necessity for preserving some smoke producing apparatus for the time when the enemt are actually in sight.

  (iii). Any vessel on the barrage hearing or sighting enemt surface craft is to report the fact without delay and proceed south or to the nearest shelter, making smoke screen or not according to circumstances. Should a vessel be near the land it may be possible that she has not been sighted, and therefore to make a smoke screen would only tend to give away her position. Under these circumstances she would close the land as much as possible with a view to escaping unnoticed.

  (vi). On information being received that enemy surface craft are approaching, the Captain of the Barrage or his representative will make a W/T message ordering barrage forces to proceed south. They may or may not be ordered to make a smoke screen according to circumstances. If this signal is not made during a “single operator” period, it will be repeated at the next “single operator” period. These messages will not be answered. Vessels already keeping continuous W/T watch should close other vessels in the line to which they are attached, choosing the vessels to windward first and repeating the signal by Long Distance code. After receipt of the signal, continuous W/T watch is to be kept by all W/T vessels until further orders are received from Captain (B).

  (v). The smoke cloud is better and spreads higher if the smoke boxes are thoroughly dry beforehand. If difficulty is experienced in igniting a red hot bar thrust into the smoke box will always succeed in igniting it.

  (vi). Special orders as to the action to be taken by destroyers will be issued to them according to their disposition.


  1. Routine Movements. The movements of vessels in or out of the barrage will be in accordance with pre-arranged orders, and the details of these movements will be promulgated. It is essential that these times shall be adhered to as far as possible, and W/T signals regarding movements should not be made unless absolutely necessary.

  2. Reporting of changes of disposition. Any changes in the disposition of the units of the Barrage Force other than those allowed for in the programme and occasions when the programme is not carried out are to be reported by the Senior Officer of the line in which they occur to Captain (B), or in his absence to Commander (B) or Lieut-Commander (B). If the message directing these changes have already been signalled by W/T, it must be assumed that they have been intercepted by all concerned.

  3. Readiness for Sea. Vessels are to prepare for sea as soon xxx after their arrival in harbour as possible Divisional leaders and Commanding Officers are to make arrangements to coal, water, provision, etc., accordingly. No leave is to be granted until such necessary work is completed, unless the granting of leave will not delay the work.

  4. Degrees of Preparedness. In order to meetthe varying requirements due to weather conditions, probable presence of otherwise of enemy submarines etc., the following degrees are laid down and may be applied to the whole or part of the barrage force:-

First Degree. To be assumed when submarine is known to be within  the Barrage or when the certainty of one passing through is practically established.Continuous W/T watch to be kept in vessels with two  or more telegraphists.

           Especially good look-out for signals to be kept.

           Best hydrophones watch-keeper to be on watch.

           Fish hydrophone to be streamed.

           Motor Launches and other small fast craft in shelter harbours to proceed to sea in accordance with operations orders.

          No routine movements of relief to be carried out xxx which could in any way interfere with hunting operations.

The Senior Officers of destroyer, sloop and Fish trawler units will use their discretion when “First Degree” is ordered as to whether on relief they return to harbour or remain at sea, bearing in mind the importance of adhering to programme, their reserve of fuel, and also the requirements of the  moment at sea.

Fish hydrophone trawlers who are at six hour’s notice or less are to prepare for sea and remain at five minutes notice.

Second Degree. To be assumed when enemy submarines are expected to pass or when doubtful reports of their presence have been received. Normal W/T watch to be kept.

 Fish to be streamed or not, according to operation orders in force.

       Motor Launches and small fast craft to proceed to sea.

       Usual reliefs to take place.

       Vessels not toshelter for weather unless sea is very heavy.

Third Degree. This represents the ordinary degree of preparedness.

5. Necessity for maintaining correct position on the chart as assigned in the Operation Orders. In the operations connected with the Barrage it is very necessary that the several units maintain the positions assigned to them. This will be especially so after the installation of the “K” tube Stations. Officers in charge of units are to make every endeavour to maintain their units in the correct position.

  Shore Navigational Lights. In order to assist in maintaining position during the night, without aiding the enemy by the employment of fixed navigational lights, moveable searchlights will be employed, and also the usual navigational lights will be lit at varying times. Every vessel will be supplied with memoranda stating the positions and times of lighting of the various searchlights, the manner in which they will be shown, and also the times at which the ordinary shore navigational lights will be lit. Reports from all Officers as to the value and the desirability of these lights, together with any suggestions for increasing their efficiency, should be furnished to Captain (B) at the earliest opportunity.

  6. Silent intervald for Hydrophone Listening. Certain intervals will be laid down during which all machinery is to be stopped and vessels kept as silent as possible while hydrophone listening is in force. The general principal of this listening periods will be that all vessels of each section or line will have the same listening periods, but that different lines or sections on the same day shall have different listening periods, in order that he sall [i.e., it shall] be impossible for a submarine, by observing the listening periods of one section or line, to that advantage of this to slip through and repeat the same tactics through the next line.

  Should a submarine be discovered in the Barrage and parts of different lines or sections become merged,. it will probably be necessary to bring the whole barrage to the same listening periods in order to avoid interference. This will be done by Wireless signal. These listening periods will not necessarily be conformed to by vessels in contact with the submarine, but should be strictly conformed to by all others. This is especially important in order to get the full use out of the “K” tubestations, which otherwise would not know whether they were listening to our vessels or those of the enemy.

  Destroyers and other vessels, unable to maintain their machinery stopped for so long a period, are to stop everything for as long as possible without endangering the machinery, and are then to start up only those engines necessary, which should be run as slowly as possible.

  The signal that all vessels except those attacking a submarine are to remain stopped during the next listening period is to be promptly carried out.

  The signal to- “Listen on by hydrophones between the times indicated in the two following groups” is to be rigidly carried out by everyone without exception, including vessels actually in touch with submarines.

  7. Duties of Officers. Officers must realise that not only are they required to give orders as necessary to their subordinates, but they must also be able to instruct them as to how to carrythem out. This applies to all but the most technical work.

  In this connection, the attention of all officers is srawn [i.e., drawn] to the necessity for the making themselves acquainted with the following:-

  (a). Control of gun-fire, gun drill, miss-fires, accidents to guns etc.

  (b). Signalling by morose [i.e., morse code] and semaphore, including a knowledge of procedure.

  (c). Use of wireless codes.

  (d). Maintenance of special gear such as hydrophone, Aldis lamps etc.1

  (e). Details and appearance of enemy vessels likely to be met with.

  8. Possible Destruction of Submarine. In any encounter with a submarine in which it is thought probable that a submarine has been sunk, every effort is to be made to obtain definite evidence the spot being buoyed if the depth of water is less than 200 fathoms, and any oil or flotsam should be recovered after an explosion.

  9. Attack. Every reasonable chance of damaging a submarine is to be acted on without delay, and every effort made to render this damage absolutely decisive. The weapons to be used are the ram, depth charges, and the gun and, in vessels so fitted, paravanes and towed charges, as many weapons as possible being employed at the same time.

 10. Whenever a vessel is able to reach a spot close to where a submarine is known to have dived not more than three minutes previously, all depth charges are to be dropped in the vicinity. If more than three minutes have elapsed, it may stilll be worth while dropping depth charges under certain conditions, such as when the submarine is believed to be damaged or going slow, if any disturbance in the water is seen, or if aircraft report submarine is directly underneath.

 11. When depth charges are dropped ahead of a wake or of a recently sighted periscope, the tendency is always to drop them too far astern of the submarine. Officers should make a point of dropping their charges well ahead. For instance, a submarine’s periscope is sighted by a vessel who then takes one minute before she is in position ahead of a submarine. If the submarine was going five knots and the depth charge was set to 150 feet, the dropping position should be 700 feet ahead of the position where the periscope was last sighted.

 12. Depth Charges are on no account to be saved for future use, and every charge available is to be dropped on any occasion of probable value.

 13. Unless local conditions indicate otherwise, charges should be dropped in accordance with the following rules:-

  (a). Set to a depth of at least 150 feet by day and 100 feet by night. Until Mark IV pistols are received, pistols are to be set at maximum depth.

  (b). Dropped at 20 second intervals by an 8 knot vessel, at 17-second intervals by a 10-knot vessel and at 10-second intervals by a 15-knot vessel.

  (c). If other vessels are in company, the ground covered by the charges is to be marked with a Calcium or other float at each end.

  (d). Charges must not be dropped within 100 feet of one another as they are liable to be countermined if less than 100 feet apart.

  14. Attacks by gun-fire against a submarine are to be carried out with the heaviest hitting gun on board, firing as fast as possible whilst the vessel closes the submarine at full speed.

  15. After dropping depth charges, ramming, blowing up sweeps etc., an early opportunity is to be taken of listening on hydrophones.

  16. Preparedness Whilst on Passage. Whilst on passage, vessels are to consider themselves as searching the area passed through. When approaching the Barrage they must conform carefully to the listening periods in force.

  17. Action on Sighting Suspicious Object at Night. When approaching a suspicious object at night, the following points are to be observed:-

  (a). Do not challenge too soon, and take great care that your challenge is correct.

  (b). Keep as nearly bow-on as possible. This renders you much less visible and almost inaudible on hydrophones.

  (c). Depth Charges and gun are to be ready at a second’s notice.

  (d). If object sighted uses the wrong challenge or answers incorrectly, assume that she is an enemy and open fire without hesitation.

  (e). If she merely delays in answering your challenge, you have to consider that she may be unable to answer or is slack in doing so.

  (f). Keep watch on your Sentry Fish or Shark Fins, in order that if suspicious object is a submarine, you will hear her immediately she starts going ahead.

  18. Danger of Capture by the Enemy. Under no circumstances should one H.M. Vessels be allowed to fall into the hands of the enemy. Before capture becomes imminent, the Commanding Officer is to cause all Confidential Books and Official documents to be destroyed. Every man on board should be made to realise the importance of this, and should know where all the papers etc., are kept and how to destroy them.

  16. Time. Greenwich Mean Time will be used by all vessels and shore stations attached to the Barrage Force. All clocks and watches are to be sent to G.M.T., and no other time is ever to be used.

  20. Bearings and Courses. All bearings and courses will be true unless otherwise stated.


  1. The Shore Office of the Captain of the Barrahe is situated at Otranto, where all reports except those of an immediate nature should be forwarded.

  2. Barrage Force. The following reports are required to be forwarded to Captain (B) from the Barrage Force:-

Copy of Hydrophone Log for period out on barrage. To be forwarded immediately on return to harbour. These are to be collected by leaders of divisions or units, who should scrutinise them and forward any remarks which it may be necessary to make.

Report of Proceedings for period out on barrage. To be forwarded by divisional leader immediately on return to harbour. If nothing of interest has occurred, there reports need not be furnished. Officers are invited to offer any suggestions for the more efficient working of the Barrage Force. These suggestions will be particularly valuable during the initial stages of the re-inforced barrage.

3. Shore Stations. Any reports which Captain (B) may call for from hydrophone, “K” Tube and look-out stations are to be sent to Captain (B’s) office at Otranto.

4. Destroyers. Captain (D) is requested to furnish Captain (B) as far in advance as possible with the names of destroyers available, proposed times of reliefs and any changes in the numbers available for the Barrage Force.

5. Aircraft. The Wing Commander will keep Captain (B) generally informed of the numbers of craft he has in readiness to answer calls from the Barrage. Such planes will be kept in constant readiness to co-operate with surface craft in hunting submarines.

Source Note: Cy, DNA, RG 45, Entry 520, Box 415. Identifier in columnar fashion at top of each of the document’s twelve pages: “1/6/D/H/J/Q.” A British officer remained in command at the Otranto Barrage until war’s end. In June 1918, thirty-six American submarine chasers joined the Allied force patrolling the barrage and would have been subject to these instructions. Halpern, Naval War in the Mediterranean, 333, 503.

Footnote 1: Aldis lamps, named after their inventor Arthur C.W. Aldis, were signal lamps typically used to send Morse code.