Answer:
Before Henry joined the army, he envisages fighting in grand battles and being swept away by their "sweep and fire" and because of this he wants to become a Greek or "Homeric" figure. He is dissuaded by his mother from joining the army but he goes against her wishes and enlists.
When he leaves for war, his mother goes contrary to his expectations and instead of convincing him to be a war hero, she gives him a simple advice.
She asks him to take care of himself and be careful and not be a rebel and fall into the group of bad soldiers. She tells him, "<em> don't know what else to tell yeh, Henry, excepting that yeh must never do no shirking, child, on my account. If so be a time comes when yeh have to be kilt or do a mean thing, why, Henry, don't think of anything cept what's right."</em>
From the quote above, his mother implores him to always do the right thing when he is faced with the opportunity to do wrong.