Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Lindon W. Bates, Submarine Defense Association
January 30th, 1918.
My dear Bates,
Your letter of December 27th, with the enclosed memorandum and the three copies of “MANOEUVERING AS A DEFENSE” were received a few days ago only. I have gone over them very carefully, and I earnestly hope that the predictions you make will be realized. Not only that they will be realized but that they will be available for the submarine campaign at the earliest practicable moment. Time is everything in this particular war against the submarine and the protection of commerce.
There have been of course endless inventions or propositions of various kinds to oppose the submarine. Unfortunately, as you say, torpedo and submarine problems were not understood by 999 out of a 1000 of these people. There can be no doubt that Admiral Benson is correct in saying that your propositions are the most important of the war, provided they will realize your expectations.
We have been very bitterly disappointed in this respect. Implements that had promised to put an end to the submarine for all time as a military weapon have shown excellent results in the laboratory but have failed of success when placed on board ship in actual service, particularly when placed in the hands of men who must handle them, and who are necessarily not sufficiently expert to handle some of the very delicate instruments that have been invented.
There would be no difficulty whatever in putting down a submarine if we can only get the instrument which will fulfil the requirement stated in my last letter to you; that is, an instrument which will enable us to keep an antisubmarine vessel within easy gun fire of a submarine that is travelling under the water. We do not even require to get close enough to him to drop a depth bomb, because if we can keep him under the water until his batteries are exhausted he is bound to come up provided he is in water too deep for him to sit on the bottom. And even if he does go down on the bottom we have means by which he can easily be located and then destroy him by a depth bomb.
I do not attach as much importance as you seem to to the question of steering “S” courses. What you say is of course mathematically correct provided your premises is right. You seem to assume that the submarine fires a torpedo from a considerable distance. All experience has shown that this is not true. We have even ascertained the fact that submarine captains are ordered not to risk missing with a torpedo by firing outside of about 300 yards. Under these circumstances it does not make any particular difference how fast a ship is going or whether she is steering a curved course or not. He can guess her speed within a few knots and he can aim his torpedo so that it will surely hit her whether his guess is very wide of the mark or not.
As for the whole question of zigzagging or steering a curved course, the only utility of it is that it prevents the submarine doing what he used to do when vessels steamed on a steady course; that is, it prevents the submarine leisurely taking a position with the ship’s masts in line, submerging, and waiting patiently for the ship to pass by, taking a peep once in a while with a periscope.
The only difference the zigzagging makes is that instead of being able to do this the submarine takes a position on the supposed course the vessel is making good. Unfortunately, geographical conditions where the submarine operates are such that the submarine almost always knows approximately the standard course. He therefore takes up a position the same as before. If the vessel has the bad luck to zigzag close by him she is torpedoed. If she does not zigzag by him he misses that chance. Zigzagging, therefore, very considerably decreases the chances of a vessel being torpedoed, but the most scientific zigzagging possible, curved or otherwise, is no guarantee that she will not be torpedoed. All this results from the fact that torpedoes are not fired at any considerable range. They are too valuable to be wasted in this way.
Regarding the effect of steering a zigzag or an “S” course on gunfire, it would be very disconcerting indeed before we had developed the rapidity of fire which now exists. This has reached a point which makes it practically impossible for an enemy vessel to keep clear of her shots no matter how much she changes her course or changes her speed. An enemy vessel is a ponderous affair, and it takes her some time to change her course or change her speed. You can therefore readily see that if you can land a shot or a bunch of shots near her every two or three seconds, you do not care a rap what sort of course she is steering or what her speed is. It is analagous [i.e. analogous] to squirting a hose on her.
Referring to the memorandum for use in connection with the U.S.S.GEM. We now attach no importance at all to the question of the range of visibility. It has been found by very extended experience with different systems of camouflage that while it is very successful in reducing range of visibility under certain atmospheric conditions, it is ineffective in the great majority of conditions that exist at sea. This is particularly true with reference to the submarine, because he views the ship from a point so close to the water that he always has her entire profile outlined against the sky.
As a result of this experience on this side, the whole system of camouflage has been abandoned. That is, they have abandoned all attempts to render the vessel less visible, and they have concentrated their attention upon what you have justly characterized “the greatest possible embarrassment to correct aiming...... from a submarine”. This is done by means of what is called the Dazzle system of painting. Generally speaking but two colors are now advocated – a very dark one and a very light one, and the ship is so painted by very large irregular patches of color, concentrated on a certain part of the ship, that it is very difficult to tell how she is heading. The effect is really most extraordinary. I have seen estimates made that were from four to eight points wrong, both in viewing the models in the laboratory and our actual vessels operating in these waters. The man who is most responsible for this system is now on his way to America to instruct our people therein.
There seems to be a more or less general opinion that if the people on board of a ship have sufficient experience and are sufficiently vigilant they can see a submarine periscope far enough away to take some action to avoid the torpedo that is fired. This single idea has been responsible for the loss of at least a million tons of shipping. It became so thoroughly lodged in the heads of some of the “principal dignitaries” that they resisted means of opposition which are now in operation.
The trouble is that this judgment was formed from the photographs or actual observation of the former type of periscope while the submarine was travelling through the water at a speed of not less than four knots. Under these circumstances you can see a periscope a very considerable distance by the wake it leaves, particularly as the periscope in question was over 4" in diameter.
The modern periscope is less than 2" in diameter and is nickel plated so that it reflects back the color of the water. Moreover, the appliances for handling the submarines are now so perfected that she can steam under the surface at a speed of not over one knot an hour and still maintain her horizontal position. In making an approach she habitually steams at a very slow speed with her periscopes completely housed. Knowing the approximate bearing of her prey she can set the line of sight of the periscope nearly thereon and by sticking it up for a very few seconds can take a bearing, then haul it down again.
In order to illustrate this feature of the practical invisibility of the periscope I looked up the records of the destruction of merchant ships for a period of about six weeks and I found that of thirty vessels destroyed off a certain port, only one had seen the periscope of the submarine before she was struck by the torpedo, and none had seen the torpedo until within two or three seconds of striking.
You will be glad to know that of the numerous instruments that have been built and installed for the purpose of detecting the presence of submarines under water, a number of those devised by the French and by the British and by the United States are now in comparatively successful operation. I am inclined to believe that the ones we have sent over here with the personnel to operate them, are somewhat superior to those of our Allies. At all events we hope that when more hunting squadrons fitted with these instruments are in operation we can make it exceedingly difficult for the submarines to operate.
This does not mean however, that the ideal instrument has been devised. While some of these will operate with the vessel going at considerable speed, there are none that are successful on a powerful vessel like a destroyer going at full speed. Of course you know a destroyer is an exceedingly noisy machine when going at full speed, both on account of the vibration of her main and auxiliary machinery, by the noise of her blowers and the vibration of her thin hull.
There is one other item that you mention which is of interest, and that is the depth shells to be fired from 5" and 6" guns. This is a matter which has been very extensively gone into on this side. Guns have been specially built for throwing depth shells. The following calibres have been built and tried out, viz:- 7 1/2", 11" and 13". These throw non-richochet depth shells having bursting charges of from 43 to 150 lbs. They have not proved successful and this for the simple reason that the amount of explosive in the shell is not sufficient to injure a submarine unless we get it very close to her. There used to be an impression that the submarine was a very delicate machine, but the experience of this war has shown the contrary to be true. I have read over the reports of a large number of British submarines that had been menaced by gun fire, depth shells, depth charges, and so forth, and it is very astonishing how much they will stand without being sufficiently injured to keep them from getting back into port. Even the very large depth charges of 300 lbs. of high explosive must be dropped quite close to them to have the desired effect. I should say roughly speaking that the 5" and 6" depth shell would not be of any use. You practically never get an opportunity of shooting at a submarine when she is on the surface. She cannot afford to compete in gun fire with any vessel having guns of sufficient range to reach her. She will use her battery to tackle a vessel that has no guns, or that has guns of less range than her own, but as soon as you succeed in landing a shell on the other side of her she invariably dives. And once she has gotten her back below the surface it is almost a physical impossibility to hit her with any type of shell.
I shall be glad to hear from you the results of any of your experiments or an account of any appliances that may be devised by your Association.
Very sincerely yours,