What do the officers say about the men in the 304th and explain why it upsets Henry in "Red Badge of Courage".
The officers know that a ferocious battle is about to begin, and one of them says to the other, "It'll be hell t'pay stoppin' them...what troops can you spare?" The second officer replies, "there's the 304th. They fight like a lot 'a mule drivers. I can spare them best of any". The first officer then notes, as he rides away, "I don't believe many of your mule drivers will get back".
Henry is astonished when he hears this exchange. The news that the 304th, basically expendable because they are not considered to be good fighters, is about to be sent into a skirmish which most of its members will not survive, makes him feel numb and "aged", but
"the most startling thing (is) to learn suddenly that he (is) very insignificant. The officer spoke of the regiment as if he referred to a broom. Some part of the woods needed sweeping, perhaps, and he merely indicated a broom in a tone properly indifferent to its fate. It was war, no doubt, but it appreared strange".
Henry truly understands at this point that he, as an individual, does not matter. He has discovered the true nature of war, in which regiments are just parts of a great machine, important only for their functionality, and made up of men whose humanity in the greater scheme of things makes no difference (Chapter XVIII).