Background
Lassen was born in Steglitz, a Berlin suburb.
Lassen was born in Steglitz, a Berlin suburb.
He sank 26 ships for a total of 156,082 gross register tons (GRT) during 4 patrols, leading to a remarkable average of 39,020 GRT per patrol. His total tonnage made him the 10th most successful U-boat ace of the war. He joined the Kriegsmarine as Seekadett on 25 September 1935.
When World World War II started, Lassen was an Oberleutnant zur See and serving as I. Wachoffizier (1st Watch Officer) on U-29 under Kapitänleutnant Otto Schuhart.
While serving with U-29 Schuhart sank 13 ships, including the aircraft carrier HMS Courageous. On 3 January 1941 Lassen assumed command over the U-29, which served as a training boat in 24th U-boat Flotilla by this time.
He ended his command on 14 September. On 16 October 1941 Lassen commissioned the Type IXC U-Uboat U-160.
Lassen spent about four months training the crew and testing the boat with 4th U-boat Flotilla, before U-160 became operational and was transferred to 10th U-boat Flotilla on 1 March 1942.
U-160 left on her first patrol in early March 1942. During this patrol Lassen sank or damaged six ships for a total of 43,560 GRT. On 10 August 1942 he received the Ritterkreuz. On 1 September he was promoted to Kapitänleutnant.
On his fourth and final patrol to South African waters in March 1943 he sank or damaged six ships in less than 5 hours for a total of 41,076 GRT during the night between 3 March and 4 March.
On 14 June 1943 Lassen was transferred away from U-160 to take up duties as a tactics instructor and commander of the "Offiziers-kompanie" in 1. U-Boot-Lehrdivision, a training unit for future U-boat commanders.
On 1 April 1945 he was promoted to Korvettenkapitän. On 15 April 1945, Lassen took command of the Pretoria, then a converted hospital ship.
Ships attacked As a U-boat commander of U-160 Lassen is credited with the sinking of 26 ships for a total of 156,082 gross register tons (GRT) and further damaging five ships of 34,419 GRT. Wehrmachtbericht reference Bibliography.