He is not fighting the enemy men so much as the swirling battle phantoms that surround him. He hears men speak around him as if he were sleeping. No one has a heroic pose. They are moving as fast as they can, reloading and then firing almost at random in the smoke in front of them. The lieutenant of the company encounters a soldier fleeing in terror and beats him back into the ranks.
Men occasionally drop from being hit.
Eventually the firing recedes, and the men begin to rejoice. They have driven back the enemy. They attempt to recollect themselves. It takes Henry some moment to come back to his senses. He realizes the grime and smoke makes him choke.