how do you get battle fatigue

Gene Kelly directs and stars in this wartime naval "training" film. Kelly plays the role of Seaman Bob Lucas, a troubled and angry "fireman" whose ship was sunk in battle. Many sailors died at sea, but Lucas lived through it and suffers from what now might be termed "post-traumatic stress disorder." After lashing out at everyone around him, Lucas comes to understand his emotions, and moves from illness to wellness, with the help of a wise psychiatrist. Kelly considered his performance in Combat Fatigue Irritability one of his very best. But no filmography lists it.