West Caddoa was a Design 1019 cargo ship built in 1919 by the Western Pipe & Steel Co of San Francisco.

[11] On June 17, 1922 while coming from Jacksonville, Florida through Bremen to Holtenau, she collided in Kiel Canal with a Swedish steamer.

She subsequently moved north and was scheduled to go to UK with a load of scrap iron with convoy HX 115 on March 17, 1941.

Empire Guillemot was chosen to participate in the Operation "Propeller", an attempt to supply Malta with single ships.

She hoisted a Vichy France flag on September 15 until her arrival off Bizerta, where she raised the Italian ensign and followed the route north toward Sicily.

Empire Guillemot was scheduled to return during Operation "Halberd" but could not sail as a result of engine defects she experienced again on October 17.

She eventually left Malta independently on 22 October 1941 at night, but the freighter was soon shadowed by the Italian naval trawler Corrispondente Beta,[17] which on October 24 vectored three SM-79 of 130 Group (two from 280 Squadron, Capitano Melley's 280-3, and Sototenente Caresio's 280-9, and one from 283 Squadron piloted by Tenente Guido Focacci) towards her west of the island of La Galite.

Empire Guillemot was hit at 14:00 by one torpedo launched by the aircraft of Tenente Focacci, and sank 30 miles off Las Rosas about 40 minutes later.