Why couldn't Henry smile in chapters nine and ten?

The men are leaving the battle; blood is everywhere, and men are dying. The youth, unhurt, feels guilty and ashamed. He doesn't have the 'red badge of courage,' the other men have earned. He's devastated. He sees Jim suffering, and he experiences death. The 'tattered man,' continues talking to Henry even though Henry keeps trying to get out of the way, and is even able to find a bit of a smile as he speaks, "The youth glancing at his companion could see by the shadow of a smile that he was making some kind of fun." The youth has no reason to smile, he can walk with the wounded, but he isn't one of them.