High Quality Content by WIKIPEDIA articles! Captain Karl-Friedrich Merten (15 August 1905 – 2 May 1993) was a German U-boat commander during World War II. He is credited with the sinking of 27 ships for a total of 170,151 gross register tons (GRT) of allied shipping. For this achievement he was awarded the Knight`s Cross with Oak Leaves (Ritterkreuz des Eisernen Kreuzes mit Eichenlaub). The Knight`s Cross of the Iron Cross and its higher grade Oak Leaves was awarded to recognise extreme battlefield bravery or successful military leadership.