U-864 was carrying German technology and material toward Japan under Operation Caesar when its damaged engine and snorkel exposed clues to Venturer's crew. A hydrophone operator heard the diesel, and an officer sighted what was probably the snorkel above the surface. Lieutenant James Launders and his officers had to estimate an unseen target's course, range, depth, and likely evasion without a fire-control system designed for this problem. They fired four torpedoes at different depths and intervals; U-864 evaded the first three but maneuvered into the fourth, producing the only acknowledged sinking by one submerged submarine of another.
Notable Point · 1:17:47-1:25:40
HMS Venturer's submerged attack on U-864
Venturer tracked U-864 by sound and snorkel clues, then solved a rare three-dimensional torpedo problem by calculation.
British SubmarinesFedjeGerman Japanese Technology TransferGerman NavyHMS VenturerHydrophonesJames LaundersJapanese NavyMilitary Technology TransferNorwayOperation CaesarRoyal NavySnorkelsSubmarine AcousticsSubmarine On Submarine CombatSubmarine WarfareThree Dimensional TargetingTorpedo Fire ControlTorpedoesType IX U-BoatU-864World War II