36 Hours (1964)

36 Hours (1964), directed by George Seaton, stars James Garner as an American intelligence officer captured by German forces during World War II. He is subjected to an elaborate deception in which he is led to believe the war has already ended in order to extract military information. The film focuses on psychological manipulation, strategy, and deception rather than action.

Från IMDB:
Germans kidnap an American Major and try to convince him that World War II is over so they can get details about the Allied invasion of Europe out of him.