Naval History and Heritage Command

Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to All Naval Forces Operating in European Waters

23 March, 1918.    

From:     Force Commander

To  :     All sea forces.

Subject: Tendencies of German Submarine in attack.

          The following figures from British Admiralty Reports are quoted for information:

          Although a total of only 110 Merchant Vessels, British Allied and Neutral, were sunk in February – the lowest figure of any month since July 1916 – the percentage of success in attack has increased from 53.4% for January to 58.3% for February. This increase was mianly <mainly> in the English Channel and on the West Coast,where the January percentages of successful attacks were 49% and 44.4% respectively.

          There was a decided increase in the proportion of attacks on vessel in convoy, the number in February representing 12% of the total attacks, compared with 5% in January.

          Of the total losses, 62.5% were in Home Waters, the increased percentage over January being due to heavier losses – 16 compared with 8 – in the Irish Sea. The Mediterranean losses represent 22.8% of the total, compared with 34.5% for January.

          But for the last 5 months, the percentage of losses to sailings for this Irish Sea is8% compared to 1.4% of the total sailing to and from all United Kingdom ports.

          Attacks during constant light and darkness have decreased; but as the days lengthen, a decided increase is shown in the number of attacks between the hours of 4.p.m. and 9 p.m.

          The number of attacks in Home Waters when the moon was up fell in February to 25% of the total attacks, the figures for January being 56%, but the percentage of success shows an increase, it being still well above that for daylight attacks. The losses of British vessels in United Kingdom overseas trades was 38%, double the January figures, but the same as those for December.

          There was a slight tendency to attack f<a>rther from shore than in January.

N. C. Twining 

By direction.