During World War II, he commanded U-boat and received the Knight's Cross of the Iron Cross (German: Ritterkreuz des Eisernen Kreuzes); during the post-war years, he pursued a career in art history and archeology.

[citation needed] Schroeteler had been transferred to the U-boat service in September 1941 and went on patrol from 23 April 1942 to 15 July 1942 on U-96 as a Kommandantenschüler (commander-in-training) under the command of Hans-Jürgen Hellriegel.

Dönitz was the former Commander-in-Chief of the Kriegsmarine, Adolf Hitler's successor as the head of state of Nazi Germany and convicted war criminal at the Nuremberg trials.

There, Schroeteler was one of the six pallbearers who carried Dönitz to his grave, all six wearing their wartime Knight's Crosses.

[7] Finally, Schroeteler allowed himself to be photographed wearing his uniform and Knight's Cross and sent signature postcards to interested people.