How successful were Captain Hardengen and his fellow U-boat commanders in destroying cargo tonnage along the East Coast?

Korvettenkapitän Reinhard was a German U-boat commander during World War II. He was the 24th-most-successful German submarine commander of the war, credited with the having sunk 115,656 gross register tons. After the war, he spent a year and a half in British captivity before starting a successful oil trading business and serving as a member of Bremen's city council for over 32 years.