HMS Venturer sank U-864 off Norway in 1945 in the first successful submerged submarine-versus-submarine attack.
The British submarine fired four torpedoes at the German U-boat on 9 February 1945. Venturer’s commander, Lieutenant James “Jimmy” Launders, estimated U-864’s course and speed from its underwater sound and plotted an interception without using sonar to guide the torpedoes directly.
All four torpedoes were launched in a spread, and one struck U-864. The German submarine sank with all 73 people aboard. The engagement is famous because both submarines were submerged, making it an exceptionally rare underwater duel.
The action is sometimes confused with earlier attacks in which a submarine destroyed another vessel while one was surfaced. Venturer’s victory is specifically remembered as the first successful attack of one submerged submarine against another submerged submarine.