Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Admiral William S. Benson, Chief of Naval Operations
Subject Copy. File No. <1/9/1>
Cablegram Sent June 28 1918 TCM
To Opnav Washington Serial No. 258
Prep. by O-1 M.T. D.R.
S E C R E T
258 Your 7454. It is the practice to keep ships proceeding westward through submarine areas in organized convoys whether under destroyer escort or not, so that submarines will sight as few ships as possible and convoy can be manoeuvred away from reported position of submarines. In general convoys should be as compact as possible in order to minimise chance of being sighted. If convoys are spread over considerable area they are likely to be seen by submarines and successful attacks can easily be delivered against one or more vessels. For large convoys not under destroyer escort the present convoy formations are considered as suitable as any. With small convoys not under escort some variation may be made from usual line formation. It is advantageous to keep anti-submarine tactics as elastic as possible. Comparing column with line it is certain that a submarine attacking a column is sure to find a target either in the leading vessel or in some of those astern, regardless of the zigzag employed. Both ANTILLES and FINLAND are successfully attacked while zigzagging in column, despite the fact that the convoys were under escort at the time. Column formation should be avoided.
If vessels are in line with close intervals the convoy may zigzag away without giving submarine chance for a shot. If convoy zigzags directly towards submarine it requires careful handling of submarine in order to get successful show at convoy. In line formation there is greater concentration of lookouts in the dangerous sectors and most valuable ships are given some flank protection. There is very little evidence to indicate that submarines attempt to take advantage of unbroken target made by several ships in line. In nearly all cases the submarine selected one ship as target and delivers attack at close range.
Line of bearing not exceeding 4 points lessens the possibility of an unbroken target but in practice this formation tends to extend into column. A formation with ships in double line with rear line close up and following interval of ships ahead or line formation with flank ships dropped back and zigzagging at higher speed can also be used. Slightyly variant formations may by their novelty tend to disconcert submarines and from this point of view are favorably considered. 09328. 258.
Source Note: Cy, DNA, RG 45, Entry 517B.