Kirby Frye, a former Confederate officer but now a Union Cavalry scout, is sent into Montana territory to locate and retrieve three Gatling Guns stolen from the U.S. Arsenal by outlaws believed to have taken them west to sell to the Soiux and Cheyenne. The trail leads him to Red Bluff where, aided by Claire Corville, he and the audience discover together and real quick like that Martin Gavin, a supposedly-honest operator of a freight line, has the guns and intends to exchange them to the Indians for furs.

While crossing the desert, a frontier scout, Jess Remsberg (Garner), rescues Ellen Grange (Andersson) from a pursuing band of Apaches, and returns her to her husband, Willard Grange (Weaver). He is contracted to act as a scout for an Army cavalry unit. Willard, Ellen, and her infant son are along for the ride, as is horse trader Toller (Poitier), a veteran of the 10th Cavalry (the “Buffalo Soldiers”). The party is trapped in a canyon by Chata, an Apache chief and grandfather of Ellen’s baby. Willard is captured and tortured. Jess sneaks away and brings reinforcements just in time to save the day. Jess learns that the man he has been hunting is none other than Willard Grange.

During the last winter of the Civil War, cavalry officer Amos Dundee leads a contentious troop of Army regulars, Confederate prisoners and scouts on an expedition into Mexico to destroy a band of Apaches who have been raiding U.S. bases in Texas.

Three trappers become scouts for a cavalry captain (Guy Madison) who loses his fort to a hated colonel (Robert Preston).