Charley is a fifteen-year-old boy from a farming family who assumes the role of the man of the house after his father is killed by a horse. Strong and tall with large hands, he lies about his age to join the Union Army, driven by a desire to prove his manhood and a fear of missing out on the excitement. He is religious and tries to maintain clean thoughts and behavior, abstaining from the heavy profanity used by other men in the camp.

Nelson is a volunteer soldier who arrives lacking combat experience but maintaining a highly confident attitude about the Union's prospects. He expects the regiment to have an easy time defeating the Rebel forces. He represents the eager optimism common among new recruits who have not yet seen the reality of war.

Charley's Mother is a widow living in Winona, Minnesota, raising her two sons alone. She initially permits her underage son to volunteer for the army because he is highly persuasive and the local consensus suggests the conflict will be brief. As the weeks pass and she reads news of the actual fighting, she grows increasingly worried about his safety.

Orren is Charley's younger brother who stays behind in Minnesota. He is a primary recipient of Charley's letters detailing the poor food and boring drills during early army training, representing the civilian family life Charley leaves behind.

Lieutenant Olafson is an officer commanding the troops in Charley's unit. He is responsible for directing the men during the chaos of early battles, attempting to maintain military order and discipline when the soldiers are terrified and overwhelmed.

The Confederate Guard is a young Southern soldier stationed across the river from the Union camp. Like Charley, he is a young farmer in civilian life. The two youths briefly communicate across the water during duty, finding common ground despite wearing opposing uniforms.