Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to the Office of the Chief of Naval Operations
Subject Copy. File No. <16-5-7>
Cablegram Sent May
20 <21> 1918. RLM.
To Opnav, Washington. Serial No. 8198
Prep. by N-3 SX D.R.
8198. Following being sent by Admiralty to its intelligence centers Quote Warn all ships crossing North Atlantic that large enemy submarines may be encountered west of 40 degrees west and on American Coast. Use otters when in 90 fathoms or less. Masthead lookouts to be stationed during daylight when north of 15 degrees N. Unquote. <00221> 8198
Source Note: Cy, DNA, RG 45, Entry 517B.