Jonathan is the central character in The Fighting Ground and the only one whose name is mentioned. At the story's start, he is thrilled by the church bell's ringing while working with his father. Although he notices fear in his father's eyes, he yearns to join the fight. His mother instructs him to find out what the bell's message is and insists he return home with the information. However, Jonathan decides to join a small group attempting to halt the advance of Hessian soldiers. Over the next day, he learns much about the realities of battle, the nature of soldiers, and his own identity. He must determine who the true enemies are and his feelings toward them.

The Corporal, who leads a small group from Jonathan's town, commands his men to confront a significantly larger force of Hessian soldiers. Jonathan feels both fear and admiration for the Corporal before the battle begins. The Corporal plays a crucial role by prompting Jonathan to rethink his understanding of who the enemy is.

During the battle, Jonathan becomes separated from the other Americans and encounters three Hessian soldiers conversing in German. Having heard terrible tales of their brutality and knowing they fight for money rather than principle, he expects them to be dreadful. However, when they don't harm him and seem to trust him, Jonathan becomes confused. The youngest Hessian even attempts to bridge the language gap and be friendly.

Jonathan finds himself in a situation where he must trust the Hessians after discovering a young boy whose parents have been killed. The Hessians prove to be trustworthy, as the young soldier aids Jonathan in burying the boy's parents and offers a prayer in German. This experience further confounds Jonathan, as he begins to see these men as people rather than just enemy soldiers.

After escaping and rejoining the Corporal's group, Jonathan, who initially suspects the Hessians of killing the boy's parents, realizes that the Corporal is actually responsible. When the Corporal demands Jonathan lead them back to the Hessians, Jonathan hesitates and questions his true allegiance. He returns with the Corporal, reenters the house where the Hessians are sleeping, and attempts to warn them. Unfortunately, they cannot understand him, and the Corporal's troops end up killing them.

Jonathan still needs to confront his motivations for wanting to save the Hessian soldiers. When he returns home, he faces his father and uncovers the true nature of his father's fears. Jonathan realizes that war isn't simply a battle between good and evil. He discovers a shared humanity with the Hessians he encounters; they seem to be decent people rather than the ruthless enemies he once thought. Despite the language barrier, Jonathan doesn't see them as much different from himself. Additionally, the most horrific act of war he witnesses—the murder of the young boy's parents—was committed by his fellow Americans, not the supposed enemy. In just one day, Jonathan gains a more mature understanding of war than many of the adults in his town.