A Horseman in the Sky by Ambrose Bierce

Carter Druse is a Virginian boy during the Civil War. One morning he decides to tell his father that he wants to fight for the union army, instead of siding with the Confederates and his state. His father respects his decision to join the Union, however he is saddened that his son will be leaving. His father let him know that he was proud of him, telling him that he must always do his duty however, Carter was then now a traitor of Virginia and he leaves to join the army. A few weeks later, near his old home he was keeping watch for enemy soldiers when he fell asleep on duty. When he is jolted awake what he views on a cliff opposite him will change his life forever. A confederate soldier sits tall on his horse. He remembers the words of his father as he decides what he must do and how to deal with the repercussions.