Captain Theodor Detmers was born on 22 August 1902 at Witten in the Ruhr. He entered the Reichsmarine, the navy of the Weimar Republic, on l April 1921. After service in the battleships Hanover and Elsass, the sail training ship Niobe and the cruiser Berlin, in October 1925 he was appointed as a sub-lieutenant to the cruiser Emden, named for the cruiser forced ashore at the Cocos (Keeling) Islands by the first HMAS Sydney in 1914.
A year in the Emden was followed by two years service ashore before being posted to the torpedo boat Albatros in October 1928. He had been promoted to lieutenant in July 1927. Between October 1930 and October 1932 he was posted to the naval staff and then appointed to the cruiser Köln. During his two years aboard the cruiser he was promoted to lieutenant commander and visited Australia in the course of a training cruise in 1933.
From 1934 until his appointment to the Kormoran, Detmers' service was mostly involved with the torpedo boat and destroyer arm of the Kriegsmarine, the navy of the Third Reich. The exception was a two-year posting to the Personnel Division of the Naval staff immediately following his promotion to junior commander in October 1937. In October 1938 he was appointed to command the destroyer Hermann Schoemann, and in June 1940 took part in the Norwegian campaign.
In July 1940 Detmers assumed command of the auxiliary cruiser Kormoran. During the Kormoran's cruise he was promoted senior commander. After the Kormoran's loss, Detmers became a prisoner of war in Australia He was awarded the Knight's Cross on 4 December 1941 and promoted captain in April 1943. He was repatriated after the war, but, having been rendered unsuitable for further naval service by a stroke while in captivity, he did not join the post-war German navy. He died on 4 November 1976.