Stephen Crane wrote The Red Badge of Courage without ever having witnessed combat. However, his use of vivid imagery, color motifs, and his ability to describe the emotional highs and lows of an insecure soldier have earned the novel many accolades.
The flag suddenly sank down as if dying. Its motion as it fell was a gesture of despair.
The passage is written in quick, staccato-like sentences, like the orders given by a commander or a newspaper reporter writing about his observations. The imagery is vivid and gives a picture of men swarming about through the smoke with the flag being the only observable figure in the melee.
The action of the battle is coupled with the struggle of the flag which highlights the struggle of the men below it. The flag itself becomes a soldier struggling in the battle, and signals the loss of the men as it sinks.