The Siege at Red River (1954)

Rudolph Maté's lavish, Technicolor Civil War action film stars Van Johnson as Confederate agent James Faraday who steals a Gatling gun prototype from the Yankees easily enough. But smuggling it South through enemy territory proves decidedly tricky, especially with detective Frank Kelso on his back, treacherous scout Brett Manning double-crossing him, and nurse Nora Curtis to protect.