James Cagney at one time was the highest ranking Caucasian black belt in judo, and displayed a little of his expertise in the early part of this movie. He demonstrated to the agents-in-training how to properly roll heels over head on a mat. He said to slap the ground to lessen the impact. This is probably the first lesson learned in judo training. Cagney had already shown his skill in another movie, "Blood on the Sun" (1945), in which he battled the villain in hand-to-hand combat in a wharf side warehouse. In the scene he does not use a stunt double.
James Cagney's character of Robert Emmett "Bob" Sharkey was originally based on the World War II director of the Office of Strategic Services (OSS), Bill Donovan (III) (Maj. Gen. William Joseph Donovan, USA, GCSS, KBE). Donovan objected to this, particularly the story element that had the OSS being been infiltrated by a Nazi spy. Therefore, the spy agency became the "077", and any of Cagney's character similarities with Donovan were removed.
Director Henry Hathaway once said of this movie, "I stole the plot of 'The Virginian' and used it. I'd always wanted to make that story anyway."
The story was based on Peter Ortiz's experiences as an OSS agent in World War II in France.
Due to military intelligence and secrecy reasons, Hollywood studios were prevented by the U.S. government from mentioning the OSS in movies during World War II, which is the case here.