From September 1939 until retiring from front line service in December 1940, he sank 19 ships for a total of 78,853 gross register tons (GRT), and damaged two others.

He entered the navy and spent his initial training on the cadet ship Schleswig-Holstein, followed by a period on the light cruiser Karlsruhe.

He was transferred to the U-boat force in January 1936 and rose quickly through the ranks and on 1 April 1939 he was promoted to Kapitänleutnant.

He went on to hold a number of staff positions, before taking command of 23rd U-boat Flotilla in the Mediterranean in September 1941.

[1] For almost 20 years until his death, Frauenheim worked at the Mobil Oil AG in the Federal Republic of Germany.