Adolf Piening Adolf Cornelius Piening ( 16 September 1910 in Süderende on Föhr – 15 May 1984 in Kiel ) was a " Kapitänleutnant " with the " Kriegsmarine " during World War II . He commanded the Type IXC U - boat , sinking twenty - six ships on nine patrols , for a total of of Allied shipping , to become the nineteenth highest scoring U - Boat ace of World War II , and receiving the Knight ' s Cross of the Iron Cross . The Knight ' s Cross of the Iron Cross was awarded to recognise extreme battlefield bravery or successful military leadership . Career . Piening joined the " Reichsmarine " in 1930 . His first assignment was to the armoured cruiser , after which he served on torpedo boats and minesweepers , reaching the rank of " Kapitänleutnant " by April 1939 . In October 1940 he moved from the surface fleet to the submarine arm or " U - Bootwaffe " . In May – June 1941 he carried out a single patrol out of Saint - Nazaire aboard ( commanded by Herbert Schultze ) as " Kommandantenschüler " or " Commander - in - Training " . Following this , he was appointed commander of the newly built Type IX submarine on 23 August 1941 . After training the boat ' s crew for several month , Piening set out from Kiel on his first patrol in command of " U - 155 " in February 1942 , with the intention of attacking shipping in American waters . On the journey across the Atlantic , " U - 155 " encountered the westbound convoy ON 67 , and after sending out a contact report that allowed several more U - boats to be to directed against the convoy , carried out an attack that sank an 8 , 000 ton tanker and a 1 , 800 ton freighter . " U - 155 " sank another ship off the coast of the United States re - crossing the Atlantic to the submarine ' s new base at Lorient , as part of the 10th U - boat Flotilla . Piening carried out a further seven patrols in command of " U - 155 " , sinking 26 ships for a total of 140 , 449 GRT , including the escort carrier , and also badly damaged the attack cargo ship . He also became well known for developing the " Piening Route " in 1943 , hugging the coast of France and northern Spain , to evade Allied patrol aircraft in the Bay of Biscay . In March 1944 Piening left " U - 155 " and was appointed commander of the 7th U - boat Flotilla at Saint - Nazaire . In April 1945 Piening made one last patrol , laying mines off Saint - Nazaire in . Piening spent more than two years as a Prisoner of war following the end of the war . In 1956 , West Germany re - established its Navy , the " Bundesmarine " , and Piening joined the new Navy . In 1959 he was appointed commanding officer of the 1 . Geleitgeschwader ( 1st Escort Squadron ) . He then held the position of Planning officer on the staff of COMNAVNORCENT ( Commander Allied Naval Forces North Norway ) and Chief of the Operations Division on the staff of COMNAVBALTAP ( Commander of Allied Forces Baltic Approaches ) . On 1 October 1965 he became team leader at the Führungsakademie der Bundeswehr , serving until 1969 , retiring with the rank of " Kapitän zur See " . He died in 1984 . Summary of career . Ships attacked . As a U - boat commander of Adolf Piening is credited with the sinking of 25 ships for a total of , one warship , the HMS " Avenger " , of and damaging one auxiliary warship , the USS " Almaack " , of .