On the evening of 21 September 1940, Schepke attacked the 41-ship Allied convoy HX.72 and succeeded in sinking 7 ships with a total of 50,340 gross register tons (grt) within only 4 hours, earning him the Knight's Cross. Schepke further distinguished himself in convoy battles against SC.7 and SC.11. From the latter convoy, he sank 7 ships within 13 hours. For his successes, he was awarded the Oak Leaves.
During a Wolf Pack night attack on 17 March 1941 comprising U-37, U-74, U-99 (Lieutenant Otto Kretschmer), U-100, and U-110 against convoy HX.112, Schepke's boat suffered depth charging by Royal Navy destroyers Walker and Vanoc. U-100 escaped, but Vanoc used her newly installed Type 286 M radar to detect the boat on the surface at a range of some 1,000 yards. The destroyer rammed and sank U-100, killing Schepke and most of his crew. It was the first recorded sinking of a U-boat attributed to radar detection. Schepke has been credited with sinking 37 ships totaling 145,842 grt.
Kurowski, Franz. Die Träger des Ritterkreuzes des Eisernen Kreuzes der U-Bootwaffe 1939–1945 [The U-boat arm's holders of the Knight's Cross of the Iron Cross 1939–1945]. Friedberg, Germany: Podzun-Pallas, 1987.; Rohwer, Jürgen, and G. Hümmelchen. Chronology of the War at Sea 1939–1945. Annapolis, MD: Naval Institute Press, 1992.