Kretschmer was the best German U-Boat Commander in World War II and is credited with having sunk more than 200,000 tons of Allied shipping between 1939 and 1941. In 1939 he commanded U.23, a small coastal submarine, which sunk the HMS Daring among others. After nine patrols in U.23 he was given command of the ocean-going submarine, this U-Boat Kretschmer perfected his technique of infiltrating convoys and then committing a surface attack. On one patrol alone he sunk seven ships. He was awarded the Knights Cross with Oak Leaves for his exploits. On 27 March 1941 U.99 and U.100 (the latter commanded by Schepke) were encircled by HMS Walker and HMS Vanos. Kretschmer and his crew scuttled their U- Boat and surrendered. Kretschmer was incarcerated in Britain and Canada for the duration of the war. He was regarded as outstanding by both sides.