Drums in the Deep South - William Cameron Menzies

Best friends Clay Clayburn and Will Denning graduate from West Point only to soon find themselves fighting on opposite sides of the Civil War. When the two men meet each other in combat, neither knows it as each is in an artillery position hundreds of yards from the other. However, the love of Clay's life, Kathy Summers, does know and tries desperately to save her two good friends from killing each other.