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Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Secretary of the Navy Josephus Daniels

30 April 1918.          

From:     Commander, U.S. Naval Forces in European Waters.

To:       Secretary of the Navy (Operations)

Subject:       Areas of Operations of Enemy submarines.

Reference:     (a) My cable #6352 of 11 April.1

     1.   Submarines along Atlantic Seaboard.

          Since the beginning of submarine warfare, it has been possible for the enemy to send a submarine to the Atlantic seaboard to operate against Allied shipping. The danger to be anticipated in such a diversion is not in the number of ships that would be sunk but in the interruption and delays of shipping due to the presence of a submarine unless plans are ready in advance to meet such a contingency.

          A more serious feature is the department might be led to reconsider its policy of sending anti-submarine craft abroad. It is quite possible for the enemy to send one or more submarines to the Atlantic seaboard at any time. The most likely type of submarine to be used for such operations would be the cruiser submarine.

     2.   Cruiser Submarines.

          At the present time there are only 7 cruiser submarines completed. All of these are of the ex-Deutschland type, designed originally as cargo cruisers and now used to assist in the submarine campaign. Then others of greater speed have been projected, but none have been completed, and the latest information indicates that the work on these vessels is not being pushed. This is rather to be expected owing to the small amount of damage done thus far by cruiser submarines. These submarines sink only 30,000 -40,000 tons of shipping in a four months’ cruise.

     3.   Cruiser submarines now in service make only about 11-1/2 knots on the surface, with perhaps a maximum of 7 knots submerged. They handle poorly under water and probably cannot submerge to any considerable depth. On account of their large size, they are particularly vulnerable to attack by enemy submarines. It is probably for this reason that the cruiser submarine has always operated in areas well clear of anti-submarine craft. If this type of vessel proceeded to the Atlantic seaboard it would undoubtedly operate well off shore and shift its areas of operations frequently. Thus far, with one exception, which occurred a few days ago, the cruiser submarine has never attacked convoys and has never fired torpedoes in the open sea, although vessels of this type have been operating for ten months. All attacks have been by gunfire, and as these cruiser submarines are slow, they can attack with success only small, slow, poorly armed ships.

     4.   If cruiser submarines are sent to the North Atlantic seaboard, no great damage to shipping is to be anticipated. Nearly all shipping eastbound is in convoy and it is unlikely that any appreciable number of convoys will be sighted, and if sighted will probably not be attacked. The shipping westbound is independent, butis scattered over such a wide area that the success of the cruiser submarine would not be large, and warwarnings would soon indicate areasto be avoided.

     5.   As there are only 7 cruiser submarines built, we are able to keep very close track of these ships. At the present time one of these vessels is operating off the west coast of Spain, en route home, two are in the vicinity of the Canaries, one is in the North Sea bound out and three are in Germany overhauling. I have the positions of all of these cruiser submarines checked regularly, with the idea of anticipating a cruise of any of these vessels to America. These vessels are frequently in wireless communication with one another, as well as with the smaller submarine, and they received messages regularly from Nauen.2 Their attacks against ships furnish an additional method of checking their positions, and I hope that we will be able to keep and accurate chart of all the cruiser submarines so as to be able to warn the Department considerably in advance of any probable cruise of these vessels out of European waters. At the moment the only one that might cross the ocean is the one now coming out of the North Sea, asthe other three have been out too long to make a long cruise likely.

     6.   Small Submarines.

          There is greater danger to be anticipated from the small submarine – that is, submarines of a surface displacement not exceeding about 800 tons. These vessels can approach focal areas with a fair degree of immunity, and can attack convoys or single ships under most circumstances. The number of torpedoes carried by these vessels is small, however, not exceeding 10 or 12, and the damage by gunfire would not be serious except to slow, poorly armed ships.

     7.   There seems little likelihood, however, that small submarines will be sent to the Atlantic seaboard. These vessels would have to steam nearly 6,000 miles additional before arriving at their hunting ground. This would mean a strain on the crew, difficulty of supplies and fuel (although their cruising radius is sufficient), absence from wireless information, liability to engine breakdown, unfamiliarity with American coast, and so forth, all for a small result on arriving on the Atlantic seaboard.

     8.   The small submarines at present operating around the United Kingdom can discharge their torpedoes and start home after about 10 days’ operation. In one case, U-53, which is considered a remarkably efficient submarine, exhausted all torpedoes after 4 days’ operations in the English Channel.

     9.   It is certain that if the enemy transfers his submarine attack in any strength to America, the submarine campaign will be quickly defeated. The enemy is having difficulty in maintaining in operation under present conditions any considerable number of small submarines. The average number around the United States3 at any time does not exceed about 10. The number is not constant but seems to be greater during periods of full moon.

     10.  Declared Zones.

          If submarines are to operate regularly on the Atlantic seaboard, it is quite probable that the enemy will make a public declaration extending the present barred zones. Public declarations were made January 31, 1917, setting limits to the barred zone and these were extended by proclamation on:

November 22, 1917.

January 8, 1918.

January 11, 1918.4

          The barred zone around the Azores was declared in November, 1917, but a cruiser submarine operated in the vicinity during June, July and August, 1917. The barred zone around the Cape Le Verde Islands was declared January 8, 1918, but a cruiser submarine was operating off Dakar and in the Cape De Verde Islands in October and November 1917.

          It is evident that the enemy might at any time, without warning, send a submarine to the Atlantic seaboard, but for repeated operations there he would probably declare a barred zone. The declaring of such a zone open to ruthless warfare would weaken all the arguments used to justify the declaring of zones in European waters. We know that the enemy would produce arguments if the military advantage warranted, but the advantage of operations in America should prove so small as not to justify the embarrassment in extending the barred zone.

     11.  Future Submarine Operations.

          The enemy is working on a new type of cruiser submarine with a speed of about 17 knots and the same battery as the DEUTCHLAND type. It is doubtful if this type of vessel will be handy under water and it is assumed that the bulk of her work will be done by gunfire.

          Convoys escorted by cruisers would have little to fear from this type of submarine; but slow vessels poorly armed would be at a disadvantage. There is some doubt, however, as to whether a convoy of vessels, even without a cruiser escort, would not make it interesting for the submarine. Altogether the type is not greatly to be feared; but it is realized that this type of vessel would have considerable advantage over the present DEUTCHLAND type of cruiser submarine.

     12.  Around the United Kingdom the small submarine seems to be committed, for the present at least, to inshore operations.

          In February of 1917 there were 30 sinkings to the westward of the 10th meridian extending as far as the 16th meridian; but in February of this year there were no sinkings west of the 8th meridian. In March, 1917 there were 40 sinkings west of the 10th meridian extending as far as the 18th meridian, but in March 1918 there were no sinkings west of the 8th meridian. In April 1917 there were 82 sinkings west of the 10th meridian extending to the 19th meridian, while in April 1918 practically all the sinkings have been east of the 8th meridian, there being only 4 sinkings west of this meridian, operations not extending beyound the 12th meridian. So far as can be ascertained, the enemy are concentrating efforts on building submarines of about 550 tons surface displacement.

     13.  The changes of areas in which submarines operate have undoubtedly been brought about by the introduction of the convoy system. Submarines operating well to the westward have small chances of finding convoys, and have the disadvantage of having to attack convoys under escort if found. By confining their operations to areas near shore, submarines enjoy the advantage of always having a considerable quantity of shipping in sight, as well as of finding many opportunities either by day or night to attack ships that are not under escort or in convoy. This is necessarily so, as there is a considerable coasting trade, cross Channel trade, and numbers of ships proceeding to assembly ports, all of which sailings are either unescorted or poorly escorted, and the submarine finds many opportunitiesfor attack without subjecting himself to the danger that he would encounter in attacking escorted convoys.

     14.  It is hoped during summer weather to make a wider use of aircraft and small surface craft to protect coastal waters. Whether results will be successful enough to drive the submarine further off shore remains to be seen. Every indication at present seems to point to the submarines continuing their operations near the coast.

     15.  The convoy system has given us a double advantage:-

(a) It has brought the submarine closer in shore where more means are available for attacking it.

(b) It has given protection and confidence to shipping at sea, and made the submarine expose himself to considerable risk of destruction in case he elects to attack a convoy.

          There are many indications that the submarines to <do> not relish the idea of attacking convoys unless the escort is a weak one or a favourable opportunity presents itself through straggling ships or otherwise. About 90 per cent of the attacks delivered by submarines are delivered against ships that are not in convoy.

     16.  Department’s Policy.

          I fully concur in the department’s present policy – namely, retaining on the Atlantic seaboard only the older and less effective destroyers, together with a number of submarine chasers and the bulk of our submarines. The submarine campaign will be defeated when we minimize the losses in European Waters. If the enemy voluntarily assists us by transferring his operations to the Atlantic seaboard, his defeat will come the sooner.

     17.  There is always a likelihood that a submarine may appear off the American coast. In the same manner, and this would be fully as embarrassing, submarines may begin operationswest of the 20th meridian. The losses from all such operations must be accepted. We are certain that they will be small, and will not, for many reasons be regularly carried on.

     18.  I see nothing in the submarine situation today to warrant any change in the present policy of the Department. The situation is not as serious as it was a year ago at this time. The Allies are getting better defensive measures against the submarine, many of which are meeting with success. The help of the U.S. Navy has materially helped in defeating the submarine campaign. Present information indicates that we are at least holding our own with the submarine, and that submarine construction is slowing down rather than speeding up. During the first quarter of 1918, we sank 21 enemy submarines, and the best information indicates that not more than 17 new boats are commissioned.5 With the coming of better weatherit is hoped that the situation will further improve.

     19.  There seems no sound reason for assuming that the enemy will transfer operations to the Atlantic seaboard, except possibly in the case of the cruiser submarines. These vessels have thus far done little damage to shipping, and it might prove good strategy to send them to our coast. In any event no great danger is to be anticipated from the present type of cruiser submarine, and adequate steps can be taken to deal with these vessels if they arrive on the Atlantic seaboard.6

     20.  This letter was prepared prior to the dispatch of my cable No.   7289 of May 1.6

/s/William S. Sims.     

Source Note: Cy, DNA, RG 45, Entry 517B. Document identifiers: in top left-hand corner “Si. 16406.”; and in top right-hand corner in columnar fashion: “1/3/4/5/J/H.”

Footnote 1: The cable Sims’ referring to has not been found.

Footnote 2: Nauen, in Brandenburg, Germany, was the German Admiralty’s largest radio transmitting installation.

Footnote 3: A typographical error that should read "United Kingdom" instead.

Footnote 4: The main idea of those proclamations is discussed in the following paragraph.

Footnote 5: The Germans lost between seventeen and twenty submarines in the first three months of 1918; Kemp, U-Boats Destroyed: 42-45; Stevenson, With Our Backs to the Wall: 323. Stevenson agrees with Sims’ tally of U-boats commissioned. Ibid.

Footnote 6: Three of the four German U-boats that invaded American waters in August 1918 were of the Deutschland class; Clark, U-Boats to America: 6.

Footnote 7: See: Sims to Benson, 1 May 1918.