The Last Rebel (1971)

It's 1865 in Missouri, and the Civil War has just ended. Rebel soldiers Hollis and Matt flee from Union soldiers that want to imprison them. Hollis then frees a black man named Duncan from a lynching, and they become a trio. Later, when Hollis wins a lot of money at the pool table and Matt doesn't get any, the two soldiers become enemies. This leads to a showdown between Hollis and Duncan against Matt and the men he has brought in to get that money.