Kill Them All and Come Back Alone
Ammazzali tutti e torna solo (original)
During the American Civil War, a Confederate prisoner, Clyde McKay, attempts to steal a box of gold from a Union prison camp. He is aided by a group of prisoners and a prison guard but he is double-crossed along the way.
Starring Chuck Connors, Frank Wolff, Franco Citti, Leo Anchóriz, Giovanni Cianfriglia, Alberto Dell'Acqua, Hércules Cortés, Emilio Cigoli, Furio Meniconi
Watch "Kill Them All and Come Back Alone" on Kanopy released in 1968. It's a action & adventure and war movie, and has a rating of 6.2 out of 10 from Imdb which is usually fine for this kind of movie.