German submarine U - 402 German submarine " U - 402 " was a Type VIIC U - boat built for the Nazi German Kriegsmarine for service during World War II . She was laid down at the Danziger Werft in the city of the same name on 22 April 1940 as ' werk ' 103 , launched on 28 December 1940 and was commissioned on 21 May 1941 , with " Kapitänleutnant " Freiherr Siegfried von Forstner in command . The boat commenced her career with the 3rd U - boat Flotilla on 21 May 1941 carrying - out training before moving on to operations on 1 October 1941 . " U - 402 " carried out eight combat patrols , sinking 14 merchantmen and one warship for a total of over 70 , 000 GRT during the Second World War . She also damaged three other ships . The submarine was a member of 12 wolfpacks . For his numerous successes , von Forstner received the Knight ' s Cross . Operational history . 1st and 2nd patrols . No ships were sunk during the first patrol which lasted from 26 October to 9 December 1941 . " U - 402 " followed the Norwegian coast from Kiel before heading west towards the Atlantic . The submarine sailed into St . Nazaire in France , after 45 uneventful days . On her second patrol , " U - 402 " damaged the 12 , 000 - ton troopship off the Bay of Biscay on 16 January 1942 , but the troopship was able to make repairs in the Azores . " U - 402 " returned to St . Nazaire on 11 February 1942 . 3rd and 4th patrols . For her third sortie , " U - 402 " headed for the US east coast , sinking a total of three ships , two of which were the 5 , 300 ton Soviet tanker " Ashkhabad " and her escort , the 1 , 000 - ton converted yacht USS Cythera ( PY - 26 ) off Cape Hatteras on 2 May 1942 . The U - boat had been unsuccessfully attacked by a US Navy PBY Catalina in mid - Atlantic on 29 April 1942 . The boat returned to the US eastern seaboard for her fourth patrol , but success eluded her . She returned to France , having been depth charged by patrol bombers off Cape Hatteras in mid - July and suffering a battery explosion . " U - 402 " limped back to France , but this time to La Pallice , on 5 August 1942 . 5th and 6th patrols . It was a different story on her fifth patrol ; the boat attacked over 20 , 000 tons of shipping , including the torpedoing of five ships from convoy SC 107 which involved the sinking of the British 4 , 753 ton on 2 November 1942 and a sister , " Empire Sunrise " , a few hours earlier . She also had plenty of success when she attacked seven ships from convoy SC 118 on her sixth patrol . 7th and 8th patrols . Her seventh outing saw her sinking two ships from convoy SC 129 . Retribution was swift ; one of the escorts , HMS HMS " Gentian " depth charged and damaged the U - boat sufficiently to force her return to La Pallice on 26 May . Her eighth and final patrol was marked with a paucity of targets and an ever increasing frequency of air attacks ; one of which involved a Wellington of 612 Squadron , RAF on 8 September . " U - 402 " was not hit , but the aircraft sustained enough damage to make a safe return to its base questionable . Loss . " U - 402 " had departed La Pallice on 4 September 1943 . On the 13 October she was sunk by a Mark 24 FIDO Torpedo dropped by TBF Avenger aircraft from the escort carrier USS " Card " .