In the year 1945, amidst the turbulent backdrop of World War II, a group of recruits boards a train bound for Biloxi, Mississippi for their boot camp training. The eclectic mix of draftees includes Private Eugene Jerome, an aspiring writer who meticulously documents his observations in a private journal; Arnold Epstein, an intellectual from New York; Joseph Wykowski, a towering figure likely to be their unit's best soldier; Roy Selridge, a boastful sycophant; Don Carney, who dreams of a singing career; and the mostly soft-spoken James Hennesey.
Upon arrival at the training camp, Jerome comments on the sweltering heat. The recruits quickly meet their drill sergeant, Merwin Toomey, who bears the scars of war, including a steel plate in his skull. Despite Toomey's jovial demeanor, his tough edge soon reveals itself when Epstein challenges his orders during muster, prompting Jerome to stumble through his response and face penalties. However, by chance, Jerome escapes punishment while the rest follow Toomey's strict commands.
Meal times prove uncomfortable, with the recruits finding the food near inedible. Toomey stops to inform them they will march 15 miles at 5 AM the next day. Epstein's objection leads to a grueling latrine duty for him, while the looming punishment for Wykowski and Selridge hangs over the other recruits. Later, Toomey’s overwhelming presence causes unrest among the recruits, who must finish their meals under his watchful eye.
On a long march through the swampy Mississippi, Toomey challenges the platoon to think on their feet when they encounter a pond obstacle. Jerome is tasked with choosing a volunteer to wade through, but finds himself at a loss until he reluctantly selects Wykowski—a decision that leads to comic misfortune when Wykowski struggles to stay afloat. As night falls, Jerome proposes a contest to share their final fantasies, igniting a spirited competition among the recruits about their wildest dreams if they had only one week to live.
The weekend brings a leave that sees Jerome and Carney planning to visit a local prostitute with Selridge and Wykowski. When a theft occurs, Toomey’s stern approach to discipline becomes evident. Tensions flare as Epstein bravely confronts Toomey, unveiling the sergeant's hypocrisy when he admits to stealing the money meant for Wykowski.
In Biloxi, the recruits encounter a reality of young women eager for dances and conversation. Their experiences starkly contrast back at the barracks, where Wykowski discovers Jerome's diary, igniting anger among the platoon as it reveals their private thoughts. Conflict arises, showcasing simmering resentments and tensions within the unit, especially when Epstein confronts the implications of being perceived as gay.
As their training nears completion, a series of events—including an unexpected confrontation involving Toomey and a gun—culminate in a dramatic moment of vulnerability and courage. Toomey’s admission of guilt before the platoon changes the dynamic between them, prompting a surprising act of unity when they collectively decide on a fitting punishment.
Eventually, when the recruits board another train for the Pacific, Jerome reflects on the camaraderie formed through adversity, recognizing the strength and dignity of his fellow soldiers. Each recruits' life trajectories unfold, revealing their aspirations beyond the Army: Selridge stays enlisted but remains a private, Wykowski returns to family life, Carney takes to teaching, Epstein emerges as a prominent District Attorney, and Jerome fulfills his dream of becoming a successful writer, weaving a tapestry of their intertwined destinies in a world forever changed by war.
