As February 1941 dawns over the scenic Schofield Barracks in Hawaii, Private Robert E. Lee Prewitt, affectionately referred to as "Prew", embarks on a new chapter in his military journey with G Company, a unit stationed in this tropical paradise. A seasoned soldier with an impressive six-year service record, Prew is a renowned bugler, having earned himself the nickname "thirty-year man" due to his unwavering commitment to his craft. However, his transfer from the Bugle Corps came at a steep price—a demotion—after he bravely challenged the promotion of a less capable bugler who had ingratiated himself with the Chief Bugler through various extracurricular activities.
Upon settling into his new unit, Prew quickly becomes the center of attention for Captain Dana "Dynamite" Holmes (Burt Lancaster), the commanding officer and ardent boxing coach of G Company. Holmes sees extraordinary potential in Prew's background as a talented welterweight boxer, pushing the young soldier towards achieving a championship title, something that could bolster the morale of his men and elevate his own career aspirations. To encourage his soldiers, Holmes offers promotions as incentives to excel in the ring—much to Prew's dismay, as he previously vowed to retire from boxing after a tragic incident where he accidentally blinded his sparring partner.
As the pressure mounts, Prew becomes the target of "The Treatment", a grueling series of hazing rituals designed to wear him down through humiliation and exhaustion. Under the command of Sergeant Galovitch, the rough-and-tumble members of the unit impose daily hardships on Prew, subjecting him to unwavering punishments to attempt to break his spirit. Nevertheless, his resolve remains impenetrable, as he steadfastly declines to yield to the demands of boxing or the whims of his superior.
Meanwhile, in the ranks, First Sergeant Milt Warden (Montgomery Clift) gradually takes the lead, demonstrating that his commitment to his troops surpasses mere military duty. While Holmes is preoccupied with climbing the ranks and engaging in extramarital affairs, Warden exhibits exceptional leadership—efficiency paired with compassion for his men. His relationship with Prew is particularly remarkable; he fosters a genuine concern for Prew's well-being and even shares a night filled with camaraderie, ensuring the young soldier returns home without incident.
In his personal life, Warden finds himself drawn into a complicated web when he discovers Holmes' wife, Karen, has been entangled in infidelity, leading to her hysterectomy. Gaining knowledge of this hidden affair, Warden gradually becomes involved with Karen, their clandestine relationship growing deeper as they grapple with the risks associated with their secret.
As Prew navigates his military life, he develops a unique friendship with Private Angelo Maggio, a hot-headed soldier with a penchant for reckless behavior. When Maggio encounters trouble after clashing with military police, Prew stands by his friend, offering wisdom as they face turbulent times together.
As Prew's nights out increase, he meets Lorene (also known as Alma Schmidt), a mesmerizing prostitute with dreams of rising above her current predicament. She hopes to find wealth through her work and eventually establish herself within respectable society, marrying a man whose integrity would render her past unimaginable. Yet, despite the allure of their bond, Lorene resolutely chooses not to marry Prew, feeling he does not meet her standards.
The anticipated boxing match looms large, leading Prew to unleash his frustrations in a violent brawl with Private First Class Isaac Bloom. The intensity of the fight leaves many questioning Bloom's capacity to compete, but he surprises everyone, defeating his opponent with a powerful knockout. This moment is soon overshadowed by a chilling confrontation between Prew and Sergeant Galovitch, who attacks him with a knife when Prew is left vulnerable. In his act of bravery, Prew fights back and defeats his assailant, though he chooses to withhold testimony regarding the weapon, resulting in a three-month sentence in the stockade.
Tragedy strikes as news breaks that Bloom has taken his own life, leaving those close to him in shock. While enduring his sentence in the stockade, Prew observes the cruel treatment meted out to inmates by Staff Sergeant "Fatso" Judson, the second-in-command at the prison. As he navigates this perilous environment, Prew reconnects with Maggio, who has become a shadow of his former self after enduring repeated beatings.
Prew devises a daring plan to transfer to the infamous "Number Two" barracks, purposely committing an infraction that leads to severe punishment. Emerging from this ordeal, he establishes connections with other inmates who inhabit this desolate space. Maggio, desperate to escape, feigns madness to secure his release, enduring brutal beatings from Judson, who suspects deception. Despite the horrors, he remains unwavering and ultimately sends a message to his friends, assuring them of his safety.
As weeks pass, Maggio's scheme succeeds, granting him a Section 8 dishonorable discharge. Although Prew never sees him again, he contemplates the profound impact their shared experiences have etched on his life.
In the Number Two barracks, Prew witnesses Judson's, brutal interrogation of Blues Berry, which culminates in a senseless tragedy—prompting Prew to vow revenge against Judson once he gains his release. Upon returning to Company G, he discovers a drastically changed environment: Holmes has been promoted and transferred, while Galovitch’s reduced rank serves as a reminder of the earlier confrontation. Days later, Prew confronts Judson in a fight that results in the latter's death, but at great personal cost to Prew.
Following this gritty escapade, Prew finds himself recuperating at Alma's home, wrestling with an existential crisis exacerbated by his growing disillusionment with military life. As their relationship begins to fray, he struggles to envision a future outside the Army, while Alma's plans to leave for Oregon without him deepen his sense of despair.
Unexpectedly, Warden emerges as a confidant for Prew, providing critical updates that alleviate his concerns about the repercussions of Judson's death. This brief period of reprieve is soon overshadowed by the looming threat of a month-long stockade sentence due to Prew's AWOL status, forcing him to hide yet again at Alma's.
Just when Prew feels he has hit rock bottom, the surprise attack on Pearl Harbor by Japanese forces serves as a stark reminder of the surrounding turmoil. With G Company preparing for deployment in World War II, Prew realizes he must return to duty and bid farewell to Alma permanently.
In the chaos that ensues, Prew's journey comes face-to-face with destiny as he is apprehended by guards for lacking identification, leading to a tragic confrontation that results in his demise. As Warden identifies Prew's remains and collects his belongings, he bids farewell to Karen, who departs for the mainland United States.
As she boards the ship home, Karen encounters a mysterious woman who reveals herself to be Lorene, a former prostitute whose fiancé, Robert E. Lee Prewitt, tragically fell in action. The coincidence resonates deeply; having been informed of Prew's fate by Warden, the realization that Lorene bears the same name as her late fiancé serves as a poignant reminder of the devastating consequences of war on those left behind.
