Following mistreatment by Indian agency authorities, Ulzana, Joaquín Martínez, breaks out of the San Carlos Indian Reservation with a small Chiricahua war party. When news reaches Fort Lowell, the commanding officer sends riders out to alert the local settlers, but both troopers are ambushed separately; one is dragged away, while the other kills the European woman he is escorting and then himself. The Apaches play catch with his liver. The woman's husband, who stayed behind to protect his farm, is captured and tortured to death.
McIntosh, Burt Lancaster, an aging U.S. Army scout, is ordered to bring in Ulzana. Joining him will be a few dozen soldiers led by an inexperienced lieutenant, Garnett DeBuin, Bruce Davison, a veteran Cavalry sergeant, and Ke-Ni-Tay, Jorge Luke, an Apache scout. Ke-Ni-Tay knows Ulzana because their wives are sisters.
From the outset, the cavalry confronts the brutal reality of the Apache war party’s methods and their sharp local knowledge. The soldiers quicken their resolve as they witness acts that test their moral boundaries, and DeBuin’s rigid Christian morality clashes with the harshness he encounters. The mission quickly becomes a lesson in caution and strategy as McIntosh and Ke-Ni-Tay weigh how best to outmaneuver a wary foe who seems several steps ahead.
Ulzana and his warriors decide to press on on foot, hoping to wear the pursuing force down, while their horses are steered back along a circuitous, safer route. Ke-Ni-Tay notices the tracks are those of unladen ponies, and McIntosh seizes the opportunity to stage an ambush that kills the decoy animal herd and two Apache escorts, one of whom is Ulzana’s son. DeBuin protests the idea of mutilating the dead boy, underscoring his reluctance to cross certain humane lines.
The war party then attacks another farm, burning the homestead and seizing two horses. A woman at the burned site is left alive but seriously injured after a gang rape, forcing the cavalry to escort her back to the fort. This move illustrates Ulzana’s broader tactic: to create situations that compel the troops to split their forces and defend vulnerable targets in order to recover steeds and undermine the defenders’ morale.
To gain an advantage, Ulzana splits the force again, hoping to lure the escort into a trap and seize its horses. McIntosh suggests a decoy plan designed to mislead Ulzana into believing his tactics are succeeding, buying time for the cavalry to regroup and counter.
Ulzana’s party ambushes the small escort, killing the sergeant and several troopers before DeBuin can arrive with the rest of the column. McIntosh sustains mortal wounds, and the surviving woman remains alive but mentally scarred by her ordeal. Ke-Ni-Tay scatters the captured horses just as bugle calls ring out, signaling the approach of the rest of the cavalry and forcing the Apache to flee. Ulzana runs on foot as the remnants of his band are killed.
Ke-Ni-Tay confronts Ulzana and reveals the Army bugle taken from his son’s body. Ulzana surrenders his weapons and sings his death song before the Apache scout ends him. A corporal suggests taking Ulzana’s head back to the fort, but DeBuin orders a burial instead, a decision that underscores his changed perspective after witnessing the mission’s brutal costs. Ke-Ni-Tay insists on performing the burial himself.
The surviving troopers, led by DeBuin, begin to return to the fort, but McIntosh knows he won’t make the journey back. He chooses to stay behind and die alone, completing a hard-won transformation from hunter to reluctant witness to the costs of war.
