A Bullet For the General (1967)

At the height of the Mexican revolution, a mysterious young American joins a gang of marauders led by El Chucho on a series of savage raids to steal guns for a powerful rebel general. But when the Gringo brings his own cold-blooded ideals to the bandits, El Chucho discovers that the real weapons of war belong to no army. In a land ravaged by violence, can true freedom be bought with a bullet.