Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Admiral William S. Benson, Chief of Naval Operations
16th October 1917.
FROM: Force Commander.
To : Chief of Operations.
SUBJECT: Confidential report concerning enemy submarine campaign.
This report is not included this week in the Force Commander’s General Report because he is particularly desirous that the information be held confidential in Operations and, in fact, not given general circulation in the Department.
During the week ending October 8, evidence indicates that a larger number of submarines – that is, large sea-going submarines – have been operating away from their base than at any previous time during the war.
Evidence indicates that a total number of twenty-seven on certain days were actually at sea from their base. The number varied from a minimum of twenty-two to a maximum of twenty-seven. Of these it is believed that a maximum of twenty-two at any one time were actually engaged in offensive operations, the others being in transit from their base to operating grounds outside of the North Sea.
With due consideration of the explanations given below, it is believed that the above number of submarines away from their bases constitutes at least 50% of the total number available for Atlantic work. This is a larger percentage of boats out than at any previous time during the war, and manifestly it cannot be continued by the enemy. The underlying reasons for trying to keep so many boats in the field at one time, and the fact that they have accomplished proportionately such small results is difficult, if not impossible,to explain. The only explanation which sounds reasonable is that the lack of results is due to a combination of the convoy system and a state of morale and efficiency with which we are unfamiliar.
It is desired to explain that a statement of the number of submarines out at any time, and the numbers actually in existence both at sea and at bases, is one very difficult to substantiate. There is every reason to believe that the Secret Intelligence Service of the Admiralty is unusually efficient – much more so even that is general believed even in official circles in England itself. It is, of course, of vital importance to keep the means and sources of such information very secret, and I am naturally not aware myself of these extremely secret sources. I can state, however, that reliable information is received each time a submarine leaves its base and returns.
Of course, once the submarines have left their base, it becomes quite a different problem to keep track of them. It then becomes necessary to draw conclusions from experience in the past as theamount of time they take before reaching their operating ground, and to carefully weigh all evidence which comes in, such as interceiption [i.e., interception] of wireless, either by vessels who overhear the enemy close aboard, or by radio direction finders, sighting of submarines, ships sunk by submarines, and other evidence based upon past experience.
It is desired to point out that it is practically impossible to obtain what might be called an opinion of the Admiralty on these questions. Each official of the Admiralty who is cognizant of the above evidence forms his own conclusions and these cannot always be reconciled.
Throughout the war the Admiralty has been, in my opinion, ultra conservative in its conclusions as to destruction or damage to enemy submarines. It is their constant aim not to call a submarine destroyed without definite and actual evidence supported beyond doubt[.] I feel sure that more submarines have been destroyed than the Admiralty claim as “certainties”. This assumption is borne out of the experience of their own submarines. Different officials of the Admiralty, as stated above, hold different conclusions and they are reluctant individually to stress their individual views.
The estimates given in paragraph 1 above are based on conversations with more than once official.
During the week ending 8 October several boats seem to have been working on the approach routes to the westward of the Bay of Biscay, but little damage was done except to sailing vessels. No convoys were here attacked. The greatest amount of damage was experienced to the westward of the Straits of Gibraltar.
A large submarine of the Deutschland type is still working in the general vicinity of Madeira and the Azores, although few reports have been received. The large area here involved and the small number of craft available, renders it practically impossible to put into force any effective offensive measures against a single submarine.
With reference to the various reports received by the Department as to enemy plans to initiate over-sea operations by a number of large enemy cruiser submarines, and with reference to the dispatches exchanged with this office on the subject, and also my report dated 9 October, further information is to hand as follows:-
Steps have been taken to ascertain the source of the information given to the Department from the French Ministry of Marine, via our Attache in Paris, which indicate that the news was received from the French Naval Attache at Copenhagen.
For reasons previously given, and which are based on past experience of the war, it is considered that this information which came from so many quarters is a deliberate piece of enemy propaganda designed to affect the disposition of forces.
The British Naval Attache at Christiania, who is reported to be an excellent officer of good judgment, has reported to the above effect. In formation is also to hand that the German Naval Attache at Copenhagen, in conversation with an allied agent, stated that his Government had not desire to irritate the Americans, as they did not think that America is very vigorously interested in the war as yet. He is also quoted recently as saying that submarines would only be used deliberately against U.S. for the purpose of attacking her troop ships when such attacks promised to be profitable.
It is the opinion of the Admiralty Intelligence Division based on careful compilations that enemy submarines never remain out from their base for more than 28 days (this being an absolute maximum) and that the usual period is eighteen to twenty-one days.
It is also their conviction that any extensive enemy submarine activity ‘en force’ in our Atlantic waters is a physical impossibility due to the necessity of supply transport and docking etc.
It is unknown whether the reports which have been submitted furnish the information desired by the Department, and it is hoped that the Department will ask specifically for any information desired.
Without officers constantly on duty in the Admiralty to see all information which flows through, it is difficult to collect all information of possible interest or value. All officials are constantly extremely busy and it is undesirable to unnecessarily take up their time. There is every disposition, however, on the part of the Admiralty to furnish us with any information desired which may be in their ability to give, but, owing to the circumstances existing and the organization of the Admiralty, it is necessary in a large measure for us to indicate what we desire to know.
WM. S. SIMS.