[4] Thorndike began working for the Supreme Command of the German Army and Navy beginning in 1941, where his job was to produce military training films.
He also directed a documentary for Ufa, Die Herrin des Hofes (Mistress of the Farm), in 1942.
[5] He was forced into the German army and sent to the Eastern Front, where he was captured and taken to Russia as a prisoner of war in 1945.
[4] East German master spy Markus Wolf claims that until the time of his arrest in Berlin, Thorndike was an operative for the East German Foreign Intelligence Service and that the agency was trying to create inroads in Hamburg's economic and political spheres through him.
[8] An East German newspaper claimed that the Thorndikes' 1956 documentary, Du und mancher Kamerad (You and Some Comrades), was positively received in the UK.
During this time he founded the East German Film and Television Workers Guild which he remained in charge of until his death.