The Bravos (1972)

Major John Harkness is the commander of Fort Bravo, a small outpost established after the Civil War to protect the settlers. Although permanently lacking in troops and provisions, he has always managed to avoid any incident with the Indians. Unfortunately, this delicate balance is undermined one day by a tragic error committed by Buckley, a wagon driver. The latter has indeed killed a group of young Indians he had mistaken for rebels whereas they were only in search of horses. All that could degenerate into a war but Harkness will not let it happen, whatever the price to pay...