Dulce et Decorum Est
How we cite our quotes:
"Bent double, like old beggars under sacks,
Knock-kneed, coughing like hags, we cursed through sludge," (1-2)
The bodies of the soldier are twisted and contorted, making their experience seem completely different from the sorts of marching that we usually see in military parades. Here they're like "beggars" and "hags" – cast-off elements of society.
Men marched asleep. (5)
Ok, maybe sleeping is the best thing that people can do in the midst of all this trudging through mud and bullets - but sleep deprivation can't be all that pleasant. Unfortunately, in this poem, it's the least of the speaker's worries.
"Many had lost their boots
But limped on, blood-shod. All went lame; all blind;
Drunk with fatigue; deaf even to the hoots
Of tired, outstripped Five-Nines that dropped behind." (5-8)
Words like "lame," "blind," "drunk" and "deaf" suggest that the soldiers have been stripped of their bodily integrity before they even enter into battle. They're almost zombie-men, stumbling through the dark with bodies that don't work anymore. And that's before the gas attack.