Stand for the Dead by Dave Case

The stench of death hung in the air as John Altar studied the massacre and tried to convince himself that his younger brother, Bobby, couldn’t have been part of this. Torn apart by the Civil War, the two brothers had fought on opposite sides, and in defeat, Bobby had fallen in with a group of Confederate raiders when released from a prisoner of war camp. Their mother’s wish was for her wayward son to be brought back to her, and Altar has sworn to do it. But how much had the war changed his brother? Riding into the Dakotas, Altar must face an unsavory lawman with a rapacious posse, rampaging Indians, and finally battle the brutal renegades in a climactic showdown.