As the movie begins, ex-boxer, current bugler, and career soldier Robert E. Lee Prewitt arrives at Schofield Barracks in Oahu, Hawaii. As soon as he gets there, he starts to face serious challenges. His captain, Dana Holmes, wants him to fight in a boxing tournament. Prewitt won't do it—he gave up boxing after blinding a friend in the ring. Holmes decides to bring the pain, forcing his sergeants and other soldiers to bully Prewitt, inflicting all sorts of unnecessary abuse on him. Prewitt's friend Angelo Maggio is pretty much the only guy on his side.
Meanwhile, Sgt. Milton Warden pursues an affair with Captain Holmes' wife, Karen. (While Warden goes along with the official abuse of Prewitt, he seems pretty disapproving of Captain Holmes.) After sharing a hot beach-based make out sesh, Karen tells Holmes about her horrible marriage to Holmes—marked by his constant affairs, and his irresponsibility. One time he passed out drunk and couldn't get Karen medical attention, causing her to have a miscarriage and lose the ability to have children.
At the same time, Prewitt and Maggio go to a somewhat brothel-ish club called The New Congress Club, where Prewitt starts to fall in love with a girl named Lorene (real name Alma). These two budding couples get closer.
After stupidly skipping out on his duties in order to go on a bender in town, Maggio gets sent to the stockade—run by a personal enemy, Sgt. Judson. Shortly thereafter, Prewitt manages to end the abuse: he stands up for himself, fighting and beating one of the sergeants, Ike Galovitch. The base commander witnesses this, discovers what's happening and forces Captain Holmes to resign.
Unfortunately, Sgt. Judson has been severely beating Maggio, who escapes and dies in Prewitt' s arms. Prewitt seeks revenge, challenging Judson to a fight, which quickly turns into a knife-fight. Prewitt kills Judson, but gets wounded himself. Meanwhile, Karen has been trying to convince Warden to apply to become an officer, so she can divorce Holmes and marry him.
Prewitt seeks shelter with Lorene/Alma to recover from his wound. But then the attack on Pearl Harbor happens, helping to decide everyone's fate for them. Warden courageously leads the other soldiers, directing them in shooting down Japanese planes. Prewitt leaves, against Alma's wishes, and tries to rejoin his unit. But his own men shoot him when he's mistaken for an invader. In the end, Warden and Karen can't stay together either, and she leaves Hawaii on the same ship as Alma, where they chat and remember.