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Commander Dudley W. Knox, Planning Section, United States Naval Forces Operating in European Waters, to Commander Thomas C. Hart, Commander, Division Five, Submarine Force, Atlantic Fleet

31 March 1918.

My dear Hart:-

     Before I forget it, Yarnell asked me to say to you that he has gotten your letter and is endeavoring to get the publications your asked for. He will send them along as soon as received.1

     I am enclosing some papers that more or less speak for themselves. The original suggestion came from Lt-Comdr Carter2 who has had six years experience in submarines.

     The Planning Section had been thinking along similar lines and put Carter’s suggestion in the enclosed form. What the British Planning Division thinks of the matter you can see from the remarks of Commander Taylor –- which are in turn replied to by Carter.3

     Meantime we have gone ahead and played some tactical games with one destroyer, carrying a kite balloon, and three submarines, one one side, opposed to a singly<e> submarine on the other side.

     The value of the games has been limited by our own small knowledge and imperfect conceptions of what submarines can and cannot do, as well as by doubt with respect to the efficiency of listening devices under the conditions of the problem. After we get into sound contact the game board fails us for the above reasons.

     While theoretically the combination of types in this way seems sound, the practical difficulties may render it inefficient.

     We therefore turn to you and request an opinion; knowing that you will not see only difficulties when it may be practicable to overcome them satisfactorily.

     From our game board work we deduced the following:

          1. Upon receipt of information of enemy position (which is frequently known with great accuracy), hunting submarines should remain under main engines and close distance as much as possible before meeting curve is reached. (So as to gain a greater arc on the meeting curve).

          2. The initial deployment of hunting submarines on the meeting curve should be at the maximum interval permitted by sound devices, and still maintain a sound barrage.

          3. The destroyer should proceed at full speed in advance of his own submarines; so as to get sight contact, or else surely to force the enemy to submerge promptly.

          4. In order to facilitate coordination --- when sound contact is made by one hunting submarine, the other two should come to the surface and deploy on either side of the submerged boat; ready to relieve her should batteries become exhausted or other necessity arise.

          This seems very little to learn I admit. But it seems to us that the scheme must be proved by experience before anything conclusive can be assumed.

          Do you believe it to be sufficiently promising to warrant a practical trial? If so when would you want the destroyer to start drilling?4

          Another point. The best hunting field is along the route the enemy must take to go to and from his operating grounds; because then you know hiw<s> general intentions and what general direction he may be expected to take. Would it be practicable, without radical logistical difficulties for you to base in the Hebrides or west Scotland?

          With many regards and best wishes for a successful campaign


Source Note: LTS, DNA, RG 45, Entry 520, Box 414.

Footnote 1: Cmdr. Harry E. Yarnell, another member of the Planning Section on Sims' staff.

Footnote 2: Lt. Cmdr. Worrall R. Carter, Commander, Aylwin.

Footnote 3: See: Suggestions for Use of American Submarines, 27 March 1918. Comments by Cmdr. Alfred H. Taylor, Royal Australian Navy, are included in the document.

Footnote 4: For Hart’s response, see: Hart to Knox, 5 April 1918.

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