At 06.33 hours on 10 Feb, 1941, U-37 fired two G7e torpedoes at a big tanker in convoy HG-53 west of Gibraltar but missed and heard later two detonations. Clausen thought that he had hit two other ships in the convoy. In fact, the Brandenburg (Master William Henderson) was hit by both torpedoes and sank immediately. The master and 22 crew members were lost. The day before, the ship had picked up 27 survivors from Courland and all except one were lost in the second sinking. The sole survivor was picked up by HMS Velox (D 34) and landed at Gibraltar.