Commander Thomas C. Hart, Commander, Flotilla Two, Submarine Force, Atlantic Fleet, to Commander Dudley M. Knox, Planning Section, United States Naval Forces Operating in European Wates
U S S Bushnell, <Bantry Bay Ireland>
5 April 1918
My dear Knox;
Referring to your letter. In such practical work as we have had with listening devices, the split comes right where yours did with your “game-board”, -we can’t hear well enough! The record to date is:-
Before leaving the States, two of these Submarines did considerable practicing at “trailing” each other. The listeners in part at least, had been previously trained in the art. It was then found necessary to make the hunted one go at least four knots otherwise, they heard nothing and got away from the hunter whenever she wished.
Since then and since we began work on this side, we have continued using the devices. In fact they have been manned most all the time while submerged and no doubt our men are far more proficient than they were. I have even [been] somewhat critisised, in some instances, for relying too much upon them. We usually hear a surface craft, (relatively a very noisy affair), sometime before we see him through periscopes. We certainly consider listening to be an importan[t] auxiliary, But, the two crucial experiences were unfavorable:-
On two occasions, our patrolling submarine has “sighted”, with enemy also on surface. In both cases, we were seen at same time, enemy dived and our boat dived on top of him to keep touch with listeners. Upon submerging, we have each time heard him at first and then lost him,--in one case fairly soon, on the other after keeping touch three quarters of an hour.
The circumstances are that while Fritsy--or any other sub--is getting down he runs hard and makes a noise but as soon as he is leveled up andadjusted, he goes very slowly, stops for as much as five minutes whenever he likes, and makes almost no noise. (With our small hydroplanes, we can be running at only two knots and can stop from that for several minutes without getting out of hand.)
Now, on the otherhand, there is no kind of craft that in any way approaches a submarine for following Fritsy with listeners. If surface craft can really do it, we certainly can. And if we can’t -- with the best gear and the best people--it may as well be given up by all. Just now we all think that if Fritsy is in [good] co[n]dition and keeps his wits, he will always get away from listeners.
But we would like very much to see that disporved. We are here, can probably be spared from patrol, are running well enough, are in advance of the British in only this one respect, (of listeners and devices) and are apparently the logical candidates for taking it in hand. We only need to be put at it AND to have your best listening experts and gear sent over to help.
No use moving our base until we are entirely ready to take up the new method. This is a good drill ground, there is a near by hunting ground sufficiently good for war experience in the matter and pulling up all stakes for a relocation might turn out wasted labor if the project didn’t pan out. Strategists must not “throw the Fleet” unnecessarily--they'll break it.
If we develop to a point where we can be fairly sure of following Fritsy, the tactics of the problem can likewise be worked up while operating from here. Its
s looking rather far ahead, but I incline to think th[e]re should not be more than two submarines in the unit. Yet I have no opinion as regards including a destroyer but think his main mission might be to keep Fritz from running away on surface before our Subs could also get up and after him. We can account for him with torpedoes if he only wont be a coward and run n away!
Now in short--and its hight time I became so) I think that with present development our present employments of boats acting independently is best. Question is--can we develope to the point of following Fritz for 24 hours when he knows we are after him. If so, the rest is easy.
/s/ THOS C HART
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