The Red Badge of Courage takes place over the course of a four-day battle during the U.S. Civil War. The novel is famous for its portrayal of war from a single perspective, that of a young, inexperienced soldier, rather than from a broader vantage point. Stephen Crane explores the psychological battles faced by an individual, which are ultimately more important than the physical battles fought in the field. Crane took a hard, realistic look at war, sparing us neither the gore nor the horror in his descriptions of fighting, injury, and death. His portrayal is so graphic that the novel is considered by most to be anti-war.
Henry’s anger at the injustice of the world cause him to be without feeling. This is the only way he can battle "courageously" at the end of the novel. This sort of emotionless stupor is what makes war possible in the novel.