What are themes in the red badge of courage?

The red Badge of Courage is a war novel written by Stephen Crane. The primary theme of the book is, as the name implies, the search of "courage" and heroism of the principal character, which starts as a "coward" character and grows.

So the principal theme may be that, the growth of a coward character into a heroic one.

There are other themes, like the view of war and how it contrasts with nature, where the wark is very dark and chaotic, and nature is colorful and organic.

Masculinity is something that is on Henry's mind a lot in The Red Badge of Courage. Like courage, Henry's idea of masculinity changes as the novel progresses. At the beginning of the story, Henry sees manliness as a brave soldier who rushes headlong into battle.