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Commander Walter G. Roper, Commander, Cythera, to Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters

U. S. S. Cythera

14 May 1918

From:     Commanding Officer.

To:       Force Commander, U. S. Naval Forces Operating in European Waters.

Via:      Commander, Patrol Squadrons Based on Gibraltar.1

Subject:  Organization of Hunting Squadrons to accompany convoys and escorts.

Reference: My letters of May 1, 1918, File 400 and May 2, 1918, File 400.2

          1.   The Convoy System as now in effect was adopted to deny the enemy the use of the gun. No one, of course, thought it would deny him the use of the torpedo. It was argued that sinkings would be reduced to a minimum, for the enemy would lack in sufficiency and accuracy of torpedoes. Now, after twelve months, we find the enemy with an abundance of torpedoes of deadly accuracy, and in <this zone> which is especially to his liking, he is doing tremendous execution with them. In other words – the individual submarine is probably sinking by torpedo to-day, as many or more ships than he sank a year ago, by the torpedo and gun-fire combined.

          2.   Convoying merchantmen is not a new solution of combatting raiders. Two hundred years ago, in the days of sail, convoys under protection of men-of-war were instituted to provide some measure of defense against raiding privateers and enemy vessels of war. But, then, as now, the plan was solely defensive, and then, as now, raiders took toll under cover of night and favorable weather conditions, often without the knowledge of the escorting men-of-war until the coming of daylight showed one or more of the convoy missing. Strange as it may seem, instances are by no means lacking for torpedoing of merchantmen to pass unknown by the escorting vessels until daylight or the wireless brings news that a submarine has come, taken its toll, and faded away into the darkness of the night and the sea. And, just as in the old days when convoying was in its youthful stages, it is recorded to-day that, like the swiftly sailing, daring privateer, who followed a convoy for days, awaiting his nightly chance for spoil, submarines have followed a convoy for two or three days and have exacted their nightly tax, in spite of every effort of the escort.

          3.   “Mystery” ships there were in the days of sail, too, but the convoy system and the herding of merchant ships together for the protection has sounded the death knell of the modern mystery ship as far as success is concerned. Submarines are to-day, chary of attacking single steamers proceeding alone and apparently inviting attack by gun-fire.

     4.   The foregoing is a necessary prelude to the proposal of a plan for minimization of submarine raiding and for the ultimate extinction of the evil. The “perfectly apparent way to rid the orchard of hornets, is to seek and destroy their nest,” but in the case of submarines, operating from what are believed to be impregnable bases, this is not altogether feasible at present. The plan is as follows:

     Organize hunting squadrons to consist of an armed yacht, as the “Killer,” and four 110 foot submarine chasers as the “Hunters.” The Chasers are the most ideal vessel known for this work and possess the following advantages:

     (a) Low original cost.

     (b) Light draft and consequently good insurance against torpedo attack.

     (c) Special type of three inch gun forward, depth charge projectors aft: ideal anti-submarine weapons.

     (d) Speed of eighteen knots and quick maneuvering abilities.

     (e) Equipped with wireless telegraphic and wireless telephone apparatus; and the latest type of listening devices.

     (f) Comparatively large cruising radius.

     (g) Marvelous sea-keeping qualities – the writer has witnessed their performance in three gales in the Atlantic.

     (h) Small crews.

     5.   One of these squadrons should accompany every convoy, not as escorts, but as hunters. The mission of the enemy submarine is to sink merchant ships and there are just two places now, where he can fulfill his mission:-

     (a) In the convoy area. (the spot where the convoy is)

     (b) In an unprotected harbor.

     6.   Hunting for the submarine on the high seas is more or less futile and might almost be compared to hunting for the needle in the haystack. The submarine must come to the convoy and since it is impossible to keep him out of the convoy, we must make sure that when once he announces himself in the convoy area, that he does not get away alive. A hunting squadron organized as above, and used as follows would, it is believed, accomplish this:

     (a) Hunting Squadron to join the convoy after it has left Gibraltar.

     (b) Hunters, (chasers) to be towed by merchant ships in middle of convoy; towed that they may have maximum cruising radius when cast off to hunt; placed in the middle of convoy to deny the enemy knowledge of their presence.

     (c) The Killer, (yacht or destroyer) to be any place about the convoy.

     7.   The formation for attack would be roughly as follows:

     (a) All hunters to be cast off when one of the convoy is attacked or a periscope is seen in the convoy area.

     (b) The killer proceeds to spot where periscope was seen or ship attacked and drop a calcium light3 and then gets clear – chasers take position as follows:

     No. 1, north of calcium light.

     No. 2, east of calcium light.

     No. 3, south of calcium light.

     No. 4, west of calcium light.

     All chasers equi-distant, one, two, three, four, etc., miles from light. All chasers to stop dead and listen – meantime convoy and escorts have proceeded on pre-arranged course.

     No. 1 chaser makes signal she hears a submarine on a certain bearing – all hunters and killer plot.

     No. 2 chaser makes signal she hears submarine on a certain bearing, all plot.

     No. 3 does likewise, all plot.

     No. 4 does likewise, all plot.

     The submarine is tracked on the plotting boards of each ship in this manner to one side of the square, where it is apparent he is going to pass out of it. If it is on the south side of the square, for example – two hunters on the north side get underway and proceed to the southward of the square and take up new listening positions, and stop; meantime the other two hunters are dead in the water, signaling the bearing of the submarine, and plotting his position. This goes on until the square draws close about the submarine, when depth charges may be dropped, or the hunters may keep hovering over the submarine until he has to come to the top, when he will be attacked by all, and captured or destroyed.

     8.   This plan is especially adaptable to the Mediterranean as the depth of water forces the submarine to keep moving and make known its whereabouts to the listeners; and in most places the clearness of the water makes possible the use of water telescope to locate the enemy in case he seeks refuge from the hunters by resting on the bottom. In sixty fathoms of water off Bizerte a scouting aeroplane plainly located an enemy submarine [sitting?] on the <bottom>. Attached to this squadron a Kite balloon vessel would make efficient service in case submarines, after attacking, sought the bottom to avoid detection.

     9.   The convoy is the best bait afloat for the submarine, and it is believed that the hunting squadron, operating with the bait, will assure his death, and in a short time exterminate the submarines.

     10.  The project briefly sketched in the foregoing has been built around the vessel under my command, the U. S. S. Cythera, a 900 ton converted yacht. Five months in the war zone, engaged almost wholly upon convoy and escort duty, has given opportunity to consider convoying from every standpoint, as well as to consider critically, the good points of the vessel and submarine chasers. Under present convoy conditions and duty, there is hardly a more poignant feeling of impotency to be gained than to stand on the bridge of an escort vessel, at night, while escorting, and to rehearse the opportunities enjoyed by submarines, and to weigh against these, the chances offered for successfully destroying the submarine. It is then, if ever, that the need of some definite offensive measure becomes apparent.

     11.  Submarine chasers have been selected in this plan because the writer has witnessed through a period of about two months cruising in their company, their excellent sea-going and sea-keeping qualities, and the opportunity that they present for more profitable action than can come from utilizing them for patrol work. The same may be said of the U. S. S. Cythera which, since being assigned to Base Nine has, roughly speaking, cruised 15,000 miles, without visible deterioration and which now is in better condition than when sheleft the navy yard. This vessel has 15-1/2 knots speed, and can sustain a speed of 13 knots until her coal is exhausted. It may be pointed out that as far as an escort ship is concerned, her loss could be easily replaced by another vessel of similar type, of perhaps less speed, but all the speed required for convoy duty, and sea-keeping facilities less pronounced than the Cythera. This vessel has, furthermore, 1500 horsepower, and is equipped with towing gear, which gave evidence of its worth when, for a considerable period, she towed at onetime three submarine chasers and a yacht.

     12.  The writer requests that he be given command of a squadron organized as above. If he is given this command, he will almost guarantee (after reasonable time for indoctrination and team work) to get every submarine that attacks his convoy.

     13.  At present writing there are thirty submarine chasers in Gibraltar, and if the project is to be put into execution, it would seem altogether profitable to divert four of these from their present assignment and permit the immediate try out of this project.4

     14.  The increasing audacity of the enemy in this area as demonstrated by his success on the 8th instant, in getting away scott-free, after sinking one of a convoy of three ships guarded by four excorting men-of-war – one a torpedo boat, demands immediate change in tactics against the submarine.


Source Note: Cy, DNA, RG 45, Entry 520, Box 387. Document: “File.....400.”

Footnote 1: RAdm. Albert P. Niblack.

Footnote 2: Roper’s letters to Sims have not been found.

Footnote 3: A calcium light is a device that creates bright illumination from the chemical reaction resulting from heating oxide of calcium to the point of incandescence.

Footnote 4: Niblack attached an endorsement of Roper's report, but noted that paragraph 13 should be changed to read, "it is evident from the sinkings no going on in the Mediterranean that some new tactics should be adopted to prevent the submarines from attacking Convoys at will. Present escort ships, it is true, can drop depth charges and keep the submarine down that is only defensive.” DNA, RG 45, Entry 520, Box 387.