Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Captain William V. Pratt, Chief of Staff to Admiral William S. Benson, Chief of Naval Operations
My dear Pratt,
Your last letter reached me when I was at Queenstown arranging for the arrival of our boats. I was there nearly two weeks, and leave you to imagine how much I was occupied. It was not possible to write from there, and when I came back to London,of course, I found stacked up a lot of work which has kept me busy ever since, so you must excuse me for the delay in answering your very interesting letter.
All the reasoning that you do in reference to the submarine campaign is correct. I would not have expected anything else from you; but the difficulty is that I am afraid the reasoning is based upon one fundamentally defective basis.
You start off by saying that the object should be to draw the lines offensively as close to Germany as possible. Everybody will agree with this, providing it is practicable. Of cou<r>se in doing this the mine field is the main thing that will eventually get the submarine, and then you say “provided you have mines enough, and that you can support that line so that it cannot be swept too often”.
You have evidently assumed that they have mines enough and that they can support the line so that it cannot be swept too often, and upon this you base all of your reasoning.
In the first place, considering the military principle involved, what you are trying to do is really to fight a concentrated force with a dispersed one. Or, rather, you are looking for some scheme by which you can hold a very long line so strongly that the enemy cannot break it in any one point by a concentrated attack. Try and do this with troops on land, assuming no aeroplanes to do the scouting, and see how you come out.
There is another thought that runs all through your reasoning, and that is that if you can prevent enough submarines getting out, you will accomplish your object, and that in order to do this you would be justified in concentrating all of your anti-submarine craft on the necessarily long line drawn around the German ports from Zeebrugge to Kiel.
In connection with this I think you have lost sight of the fact that if the Germans can manage to get a very few submarines out through the line each day and a very few in through the line, she accomplishes all she wants. It is estimated that Germany has about 150 or 160 submarines: that not more than thirty or thirtyfive are ever out at the same time operating off the Channel in the British Islands. Others are on the way out, others on the way back. You can readily make a calculation as to how many would have to pass out through the lines and in through the lines each day in order to keep up the thirty or thirtyfive in active operation on what we might call the Western Front.
It has been found wholly impossible to hold thin interior line in such a manner as to keep holes from being made in the mine fields. Such a hole is known to the people who make it, but for quite a time it may not be known to exist by the people who planted the mines. There are not enough ships that are owned by Great Britain to hold the line that I have indicated in such strength that a concentrated attack cannot break it at any particular point. This has been tried by all types of vessels including submarines and the losses have been so severe and the successes so little that it had to be abandoned. In fact, it may be said that there was no element of success at all; that at all times the Germans had been able to get out all the submarines that were ready to go to sea and bring back all that were ready for refit. Of course, they have suffered in this operation to a certain extent. It is known that they lost some submarines by mines, but only a very few. It is assumed that they have lost some others that the British do not know about but probably not many. The fact remains that the ingress and egress of submarines into the North Sea has been practically unrestricted.
Of course there does not exist enough mines, hardly in the world, to make a continuous line across this great distance. The method adopted is to stagger mine-fields and to place them in such positions as to render the whole area from Horn Reef west and then South <to> Texal [i.e., Texel] Island very dangerous ground for those who do not know the position of the mines.
Assuming therefore that it is not practicable that the forces available could keep the submarines from coming out, it is wholly inevitable that the submarines must be attacked after they are out. The submarines are generally disposed before all passages leading into the North Sea, the Channel or the Irish Sea. They are now up against the proposition mentioned above, that is, of establishing a dispersed line sufficiently strong to resist the attack of their enemies – their enemies in this case being merchant ships which want to get into Port. If all merchant ships came in on the same track and the submarines could be concentrated thereon, the submarines would have a fine harvest. These ships are brought in first on one route, then on another according to the disposition of most of the submarines and where the submarines are congregated at the thickest they are attacked by patrol boats, destroyers, mystery ships and so forth and so forth, in the effort to make their attacks upon the commerce as ineffective as possible.
In this attack of anti-submarine craft upon a submarine, the various appliances of which you know are being used. Generally speaking, these are the ram, the gun, the depth charge and the mystery ship of various types. Other appliances are now under construction, the principle one of which is mortars all the way from 7.5 to 13" for throwing the depth charge when a periscope is observed within the range of the mortars.
In any particular area that they want to keep clear of submarines, it is found that this can be accomplished if there are enough boats to keep the submarines below the water most of the time during daylight. Added to this, valuable ships are escorted during daylight through the danger zone. In such areas the loss of shipping is light. This is the case in the area within which our destroyers are now operating. This has a singular effect on the relation between the disposition of the submarine and the traffic that is coming in on other routes. Of course the submarines know the areas that are most completely patrolled. They exchange signals every night and get word from Berlin every night. When they find that a certain area to the Westward is quite completely patrolled they form the conclusion that that area is being prepared for the entrance of merchant shipping and they naturally concentrate their submarines therein. This is the case at the present time, and there are other areas of entrance to the Southward in which many ships have been passing in and out without any casualties at all.
From all of the above I think you will see that the necessities of the PRESENT- note that I spell this word in capitals – are a multiplication of patrol craft as rapidly as possible. To build a hundred thousand mines would take a long while. To lay them down would take a long while, and in the meantime if effort were concentrated upon this instead of upon building patrol boats (and labour is excessively scarce) the submarines would have a harvest.
Do not forget in all this business the extreme value of the element of time. Whatever is done must be done as soon as possible against the submarine. The presence of our flotillas on this side is of more value than five hundred thousand mines four months from now.
I do not know whether or not you have seen all my cables. I hope that you have. If so, my last cables in reference to your being assigned as Chief of Staff should have impressed somebody with my necessities. I think they should realize that my estimate of the situation over here in respect of the kind of man I need should be taken.
It would take a long while to explain how very difficult and delicate was the situation that I had to handle, due to the peculiarities of certain of the officers with whom I had to deal. Before I had anything to do with them I was warned by the Admiralty of this probable difficulty and the opinion was expressed that we would not be able to get along with them. I have been able to smooth over these difficulties, at least, temporarily. Moreover, I believe that I have removed certain frictions between officers of the Admiralty and those in the field who are concerned in this anti-submarine campaign. Of course it is my desire to keep these relations as they are now and that is why I wanted a man to work with me who knew me and my methods and whose methods, temperament, training, culture and character were known to me.
I have only Babcock and Daniels to help me, and to say that their assistance is inadequate to handle all that I would like to be able to handle is putting it very mildly.
With reference to your idea of the non-sinkable vessel, that has long since been realized and put into practice on this side. The monitors with whose design you are acquainted, were the first vessels of this kind. There are others that are entirely filled with wood with the exception of space enough to carry their fuel and their provisions. Some of these have been torpedoed in the engine room and have still remained afloat. There are many of these nowoperating against submarines, and they are more effective than any other type. These are the famous “Q” ships, usually called “Mystery” ships. When this war is over and I have an opportunity I will spin you some yarns about them which will give you a profound respect for the qualities of the Anglo-Saxon race and British seamen in particular.
I have not heard of any difficulties arising from mines getting adrift. An anchored mine that gets adrift and floats on the surface is a disagreeable object but not a very dangerous one; the mine must be submerged in order to get in effective work. The British drag out on an average fifteen to twenty mines a day. These are laid by submarines within restricted areas. That is, they are laid within sight of navigation marks so that the submarines can keep clear of them subsequently.
Submarines are used quite effectively in opposition to submarines. There are whole areas of entrance toward the British Isles that are patrolled exclusively by submarines. It would be very advantageous to use both submarines and destroyers and patrol boats in the same area, and it would be done if they could devise a system of recognition signals that would be certain in operation both day and night and that could not be imitated by the enemy submarines. The recognition signal must be sufficiently continuous to remove the danger of the loss of the submarine. British submarines have, upon occasions, been fired upon by British patrol vessels and very seriously injured and they have been forced to send them into separate areas. They have developed on this side Hydrophones that are very reasonably efficient. They also act as Direction finders, but their inherent defect is that the ship using them must be stopped, or going very slowly, in order to hear the sounds of the submarine. This immediately places the ship using it in great danger of being torpedoed. No destroyer that is operating in a submarine area ever stops or goes slower than 15 knots, because she never knows that there is not a periscope looking at her within torpedo range and at a distance which a periscope is wholly invisible.
A favorite trick of the submarine is to hide behind an abandoned boat in the hope that some patrol vessel will come up to see if there is anybody remaining alive in it. They have learned better than to do so. They always put the sun at their back and approach it on full speed and with frequent changes of course. Some vessels are fitted with a net projecting over the side so they can run by a boat that has survivors in it and let a few jump for the net as she passes by. This to illustrate the necessity of keeping under way.
The Secret Service of the British Admiralty is really very extraordinary. There is little they do not know of what is taking place in enemy countries. All the coast where submarines might get supplies, is under close watch, and I have been informed that there is no record whatever of any submarine ever having obtained any such supplies. Moreover, the evidence is entirely complete that none of the submarines ever need an extra supply of oil, and this for the simple reason that their endurance in oil is greatly superior to their endurance in offensive weapons and in personnel. They start out from their bases in an awash condition with their immersion tanks filled with oil and these are not emptied by the time they arrive at their hunting ground. The larger boats remain out a month, if they can stand it. If the weather is particularly bad they sometimes have to put in long before that. They have been known to go into bights and coves where the water is deep and lie on the bottom for a rest, but this can only be done where there is no ocean swell. It may be possible that on a friendly coast, like Ireland, they may have been able to get a chicken or a piece of fresh meat, but I think you can safely dismiss from your mind any idea that submarines are operating from any of the bases except those that are well known.
I am very much disappointed that the Navy Department will not send you over and I am very much flattered that you consider my asking for you such a compliment. I have been very much afraid that they might send me some other Captain whom I could not use in the delicate situations where I wanted to use you.
Up to the present time everything has gone well, and my relations with the British officials, both civil and military, and both at the Admiralty and in the “field,” are everything that could be desired. This applies equally to the French.
We are remaining as cheerful as possible under the circumstances:
Always sincerely yours,