The 1981 film Das Boot cemented an image of the U-boat war as doomed, claustrophobic tragedy, ending with a crew wiped out in an air raid the moment they reach port. The real submarine that inspired it, U-96, tells a different story: across its active combat patrols it never lost a single crew member while sinking 27 ships. This episode traces the life cycle of a Type VIIC U-boat commissioned at Kiel in September 1940, from its lethal early patrols under Heinrich Lehmann-Willenbrock to its retirement as a training vessel at Königsberg and its inglorious end under American bombs in a Wilhelmshaven basin in March 1945.

Along the way, the episode digs into the messy mechanics of 1940s submarine warfare: temperamental magnetic torpedo detonators, a Dutch freighter that survived two torpedoes and had to be finished with the deck gun, an attack abandoned in violent Atlantic swells, a stray torpedo that sank the wrong ship, and the misidentified troopship Anselm that went down with 254 people. It also covers the seventh patrol of October 1941, when war correspondent Lothar-Günther Buchheim came aboard and shot more than 5,000 photographs, a patrol that included a secret night resupply in neutral Vigo, a bombing by a Swordfish aircraft, and a surreal encounter with a Spanish ship carrying Jewish refugees that a missed torpedo spared.

• How the diesel-electric hybrid design forced U-boats to surface to breathe and recharge their batteries
• Why commanders surfaced to use the 8.8 cm deck gun instead of spending one of only 14 torpedoes
• Wolf pack attacks, 45,000 tons sunk in a single patrol, and the Knight’s Cross for Lehmann-Willenbrock
• Corvettes, depth charges, and 32 bombs from a Sunderland: how the hunter became the hunted
• Why Buchheim’s novel and Wolfgang Petersen’s film chose a fictional tragic ending over the real survival story