The Fighting Ground is written in the third person. You can tell because the narrator is referred to as “Jonathan” and does not refer to himself as “I.”
A third person narrator uses names and third person pronouns to follow the main character. The pronouns like he and they are used to refer to the narrator, not I or me. This limited narrator can follow one character, and an omniscient narrator can follow other characters as well and give a more developed picture of the other characters’ actions.
Jonathan could hear the breathing of all men about, quick and agitated. Beyond that, he heard the tap-tapping of the drum, the nagging, relentless curl of the fire. (2:30, p. 37)
The book focuses on telling events from Jonathan’s point of view of one day. Yet Avi does not choose a first person narrator. This distances the reader from the narrator somewhat. The novel uses realism like Crane's The Red Badge of Courage, which is also about a young soldier. In each case, no one is named or close to the narrator.