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Captain Joel R. Poinsett Pringle, Chief of Staff, Destroyer Flotilla, to Commanding Officers, Destroyer Flotilla






26 June 1918.

From:  Chief of Staff, Destroyer Flotillas.

To:    Destroyer Flotillas.

Subject:  Offensive Action Against Submarines Attacking Convoy.

References: (a) Force Commander’s1 Letter of 14 June 1918.

(b) Report of Conference held at the Admiralty May 28, 1918.

     1.   References (a) and (b) are quoted herein for the information of the Flotillas.

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     1.   A conference was held at the Admiralty on May 28, attended by representatives from Queenstown, Buncrana, Devonport and Milford Haven.

     2.   The conference was called to bring about an interchange of opinions in the best methods of offensive against submarines attacking convoys.

     3.   No decisions were reached by the Conference, though Enclosure <Reference> (b) gives a brief of the subjects discussed.

     4.   It was decided that all forces should have a doctrine covering appropriate methods for launching an effective attack against a submarine proceeding to attack a convoy.

          The records show that it is very unlikely that submarines will operate within 10 miles of each other, and in general this distance is considerably greater. It was the sense of the conference, therefore, that the nearest half of the escort could be withdrawn to deliver an immediate attack, escorting forces to rejoin immediately on completion of the attack,with the exception of one or more destroyers left to keep the submarines submerged until the convoy was over the horizon.

     5.   The method in use by Devonport of delivering an attack was acknowledged to be superior to any used at the other stations. The method used is as follows:-

     The destroyer sighting positive evidence of the presence of a submarine immediately hoists a large black flag, and proceeds to the attack at 20 knots, taking a course that will permit the destroyer to arrive quickest at the probable position of the submarine. The compass course is hoisted, and the destroyer with the black flag is taken as the guide. Other destroyers run parallel courses to the course set by the guide. The guide begins to drop depth charges when in favorable position, and plants marker buoy at the most probable position of submarine. Other destroyers lay parallel lines separated approximately 200 yards, then turn on opposite course and complete the barrage. The standard of speed of all vessels is understood to be 20 knots.

     Devonport representatives stated that they had found it very necessary to have a compass signal so that other destroyers could operate freely.

     6.   There was a general opposition to attempting to lay a barrage by turning, as the chance of success in damaging the submarine depends on speed with which escort vessels reach last known position of submarine. The method of turning is not adapted for use when more than one or two destroyers are engaged in the attack, and it was considered that the method of laying a barrage in parallel lines offered the best chance for success.

     7.   It should be understood that this conference was called merely for an interchange of opinions, and that the points forwarded in Enclosure (a) have never been approved by the Admiralty, nor promulgated.

/s/ SIMS.

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     1.   A conference was held at the Admiralty on May 28th to discuss measures for increasing the efficiency of offensive action against a submarine attacking or attempting to attack a convoy.

     2.   General agreement was reached on the following points:-

(a) In open waters, if a submarine is sighted ahead of a convoy, i.e. inside the probable danger angle, at any distance up to about 4 miles, at least half the escort force (if composed of T.B.D’S) should immediately proceed to the attack. The number of depth charges to be expended should vary from a large proportion of those carried when submarine leaves any definite traces, to a small proportion if there is nothing to indicate the position of the submarine, the action in the latter case being a general deterrent as opposed to a vigorous attack.

(b)  The nearest destroyer, probably in most cases the destroyer which sights the submarine, should in addition to bombarding the probable area, drop a mark buoy to indicate where submarine was sighted. Other T.B.D’s as they arrive should bombard the “likely area”. This area can only be guessed, but the assumption can be made that the submarine, after being sighted or after firing her torpedo, will probably turn away from the convoy and will proceed at an average speed of about 200 yards a minute.

(c)  It was agreed that successful counter-attack on a submarine was almost entirely dependent on the early appreciation by the escort as to which ship had been fired at, and from which side the attack was made.

     It was not thought advisable at present to add to the lists of signals that were already imposed on merchant ships, but it was considered desirable to impress on them the necessity for a ship attacked or sighting a torpedo, immediately making, and continuing to make, the signals laid down. If the track only is seen, and it is not certain from which side the torpedo came, the siren signal only should be made. Signals should not be repeated by any ship which has not seen the submarine or torpedo track.

(d)  It was considered inadvisable that any ship of the convoy should use a gun as a means of drawing attention to the submarine, as this leads to much indiscriminate shooting, which may sometimes be dangerous to the escort, and in any case leads to confusion.

(e)  At night time when the first information of the presence of a submarine is the explosion of a torpedo, the general feeling of the conference was that some organized bombardment of an area astern of the position where steamer was torpedoed should be carried out.

(f)  Disposition of escorts. The general opinion of the conference was that on account of the great increase in the number of depth charges carried by the escort and the deterioration of the enemy’s morale, it was permissable to try the effect of modifying the disposition of the escorts in favour of the offensive positions. This was not taken to mean that the usual escorts ahead of the convoy should be reduced, but that the wing escorts might be stationed further aft. In cases where the strength of the escort permitted, one destroyer should be stationed astern zigzagging across the rear of the convoy.

     In the case of troop convoys, it was considered that the dispositions at present in use for troop convoys should be adhered to.

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     3.   In order further to develope offensive action by the escort when definite evidence is obtained of the presence of a submarine, it is considered desirable that possible improvements in the present procedure should be considered and tried in the various areas, (a) a further conference being held or (b) reports being forwarded at the end of 6 (?) weeks on the experience gained.

     4.   Some of the points which appear to require development and consideration are:-

I.   Methods of immediately informing all ships present that submarine has been sighted.

II.  Methods by which the ship struck can quickly inform the escort of the fact, and as to which side she was hit.

III. The proportion of the escort force that should take part in the offensive action.

IV.  Methods of proceedure of such a force.

V.   Length of time it is permissable for attacking force to be absent from the convoy.

VI.  Offensive action to be taken by escort when a ship is torpedoed at night.

VII. The relation to the ship struck of the area in which submarine is likely to be.

     5.   As regards dispositions of escorts, S.N.O.’s of escort forces have permission for the present to modify at their discretion the position of escorts (as laid down in C.B. 620) in the direction suggested in par. 2(e)

          Commodores of Mercantile convoys will be informed of the conclusions reached at the conference, and that approval has been given to more offensive dispositions of the escort being made tentatively.

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     2.   It is desired that Commanding Officers take this subject under consideration and be prepared to discuss same in conference. Such ideas and plans as Commanding Officers may have should be ready for presentation at this time.


Source Note: Cy, DNA, RG 45, Entry 517B. Identifiers “Refer to/No. 980-12.” and “(F-12)” appear at the top of the page.

Footnote 1: VAdm. William S. Sims, Commander, United States Naval Forces Operating in European Waters.