It is April 1941 at Schofield Barracks, Hawaii and Pvt. Robert E. Lee Prewitt is new to G Company. He is a skilled boxer who unintentionally severely injured a fellow soldier in an exhibition boxing match. As a result he refuses to be a boxer anymore. This places him at odds with his company’s commanding officer, Captain Holmes, who uses the reputation of many of the sergeants in his company as skilled boxers to further his military career. Facing pressure from the fascist Gen. Barney Slater, Captain Holmes has many of his sergeants harass and abuse Prewitt in an attempt to pressure him to join the company's boxing team. Prewitt is tough and refuses to bend to the pressure. The company's First Sergeant, Milt Warden, attempts to help Prewitt, but there is only so much he can do. Prewitt becomes involved with Lorene Rogers, a local prostitute. Prewitt's friend, Private Angelo Maggio, is sent to the stockade after being court martialed for getting drunk and fighting with MPs. Things take a turn for the worse when Pvt. Prewitt is sent to the stockade for a few months of what turns out to brutal mistreatment at the hands of the Sergeant of the Guard at the stockade, Sgt. Fatso Judson, a bully and a sadist. While in the stockade, Prewitt reunites with Maggio and finds that he has been nearly beaten to death by Judson. Maggio dies after panicking and falling out of the ambulance on his way to the hospital. After Prewitt is released from the stockade he tracks downs Judson and kills him in a knife fight. Prewitt is wounded in the fight and he takes refuge at Lorene's house while he heals. Captain Holmes is promoted to major and leaves the company. The new company commander does not care about the boxing team. On December 7, 1941, the Japanese attack Pearl Harbor and Schofield Barracks. First Sergeant Warden organizes the men of his company. He and the other sergeants of the company go to the armory and get Browning Automatic Rifles (B.A.R.s) and .30 caliber Model 1919 machine guns and return fire to the attacking Japanese warplanes. Warden and his men shoot down one of the Japanese "Zeros". Wanting to join in on the upcoming war, and with Warden promising to help smooth things over regarding Fatso's murder if he reports back, Prewitt attempts to rejoin the company but is mortally wounded by a nervous sentry that same evening. As he lays dying, he says he knows that Sgt. Warden will take care of his body (make sure his death is marked "line of duty") and makes sure that it gets a military burial. After he dies, Warden assures the guilt-ridden sentry that Prewitt's death was going to happen one way or another. When asked by the other soldiers if Prewitt was a good soldier in his company, Warden replies, "Hell, he was the only soldier."