What is the theme in Soldier's Heart by Gary Paulsen?

One major theme in the novel, Soldier's Heart, is inner struggle. Throughout the novel, Charley struggles with decisions he has to make, as well as actions that he has commited to make. He struggles with his decision to join the army, he is torn by the army's pillaging of farms along the way, he fights to overcome his fear, and he struggles to control the violence that becomes habit.