In the period between the two world wars, the US Army still relied on cavalry to help in battles and to quell minor disturbances. The aging Colonel Owen Stuart (Rod Steiger) is replaced by Colonel John Hardesty (Bob Gunton), who makes no secret of his ambitions for the modernization of the U.S. Army, but that includes the destruction of most (about 500) of the Army's horses. A newly commissioned Lieutenant Marshall Buxton (Craig Sheffer), who met Stuart's daughter Jessica on the way to the base, is ordered to command the operation to his dismay, but along with his subordinates Sergeant Jack Libbey (Don Johnson), Sergeant Thomas Mulcahey (John Dennis Johnston), Sergeant James Shattuck (Robert Colleby), and Sergeant Sean Quinlain (Neil Melville), after witnessing the massacre of the first hundred horses (who were machine-gunned and slowly dying in a mass grave), rebel and decide to rescue the remaining 400 horses, claiming that they did not receive written orders. They ignore Major Forest's orders and drive the herd away.Major Forrest and Sergeant Gruber are ordered by Colonel Hardesty to capture the traitors and bring them back. Buxton and his men drive the herd from the Mexican border to the Canadian border, where they plan to hide from the army and donate the horses to the Sioux who live on the reservation. They are pursued by Colonel Hardesty's motorized force, but Buxton's sabotage (such as cutting a bridge) makes conditions difficult, and by several riders under Sergeant Gruber, who try to cut off the fugitives and bring them to Hardesty, who has cannons at his disposal.Buxton's men are soon overcome with despair at so great an action, and the lieutenant decides to go to Tucson for help to Colonel Stewart, who gives him a map and some advice. Jessica is touched by the lieutenant's efforts to save the horses and decides to write a newspaper article about their heroism, though she can hardly find anyone in the country to publish it due to Hardesty's influence. Meanwhile, Buxton's group continues on, overcoming the difficulties of winter and food shortages in the process. Several horses have to be put down due to injuries and exhaustion, and Lieutenant Shattuck in particular becomes increasingly vocal in his disapproval of the action, which he calls "hopeless". Despite his misgivings, however, he continues with the others. They soon run into trouble, however, when they see Hardesty's camp right in front of them. Lieutenant Libbey proposes a night breakthrough through the camp, which succeeds, and although Libbey is shot in the leg, the group continues on without loss. Meanwhile, Colonel Douglas MacArthur meets with Owen Stuart, whom he blames for the media pressure he is facing after Jessica wrote her article.He admits that he has nothing against horses, but is concerned about the impending world war and the uselessness of cavalry against modern German and Japanese tanks. Because of the shooting while killing wounded and exhausted horses, Major Forrest gets on the trail of Buxton's group. During one of the reconnaissances, Sergeant Mulcahay clashes with Forrest's cavalry unit and is shot while escaping. Sergeant Gruber orders him buried with dignity despite the disapproval of his subordinates, giving Buxton the upper hand. Meanwhile, he and the rest of his men and horses arrive at the Canadian border, only to find Hardesty already waiting for them there. Lieutenant Forrest gives them one last chance to surrender and stand trial, to which Buxton replies: "We're not surrounding the horses. You do whatever you have to do." Buxton separates his men and slowly, so as not to raise dust, makes his way to Milk River, which forms the Canadian border. As they flee across the open plain, Hardesty's men open fire on them, but they fire high and to the side, causing no damage to the horses. In fact, Jessica's article catches the attention of President Roosevelt, who decides to pardon the rebels. Buxton and the others cross the river and the Canadian soldiers, after assuring them that they have broken no law in Canada and that all they want is to keep the horses alive, let them go. Lieutenant Buxton decides to turn around and stand trial. For the night before the horses were to be shot, a drunken Libbey, smashing furniture and about to shoot him, told him that he hated what the world was becoming.Buxton agreed and said, "So do I, Sergeant." Libbey saluted his superior, but Buxton offered his hand. He then turned his mare around and headed back while Libbey, Shattuck and Quinlain, along with several Canadian soldiers, led the rescued horses away.