Arrow in the Dust (1954)

Army deserter Bart Laish decides that the best way for him to get away is to join a wagon train headed for Oregon. They're about a week ahead of him and on the trail Bart comes across an old friend, Major Andy Pepperis who is dying from wounds received in an Indian attack. He warns Bart that the Indians will next attack the wagon train and afterward finds the army station, Camp Taylor, destroyed. He assumes Pepperis' identity and catches up to the wagon train taking command of the soldiers escorting it. He proves to be a capable leader and quickly gains everyone's respect. As they get closer to their destination, Bart is closer to being caught and has to decide if and when he will leave them.