Blood on the Sun was filmed in 1945 and based on a true story.
Here's a snippet from TCM:
"The fight scenes in Blood on the Sun all involve judo. Cagney trained in the art extensively and even kept it up in his private life, writing in his memoirs, "I grew so fond of judo I used to keep in shape with it until a back injury I picked up doing something else put me on the sidelines." Cagney's judo instructor was a former L.A. cop named John Halloran, who in the film has a small role as Japanese "Captain Oshima." (In a sign of the paranoia of wartime America, Halloran resigned from the LAPD after the police commission sent FBI agents to investigate him because his favorite sport was judo.)"
Cagney was apparently a 1st Dan when he stopped training.
