What happens to make it possible for Henry to carry the flag?

Three men in front of the flag begin to yell to move. The flag sways proudly in the breeze. With a lunge, the men go forward and over the small field. They run and duck as they go. As he runs, Henry is filled with a fondness for the flag, marveling at its beauty and invulnerability. Because it still swayed proudly, he endows the flag with power. In the rush, the color sergeant is hit. He sways where he stands. Both Henry and Wilson jump for the flagpole. The dead man will not let go, still doing his job. Soon the two have wrenched the flag from the corpse's control.

(Chapter 19)