Bent double, like old beggars under sacks,
Knock-kneed, coughing like hags, we cursed through sludge,
Till on the haunting flares we turned our backs
And towards our distant rest began to trudge.
Men marched asleep. Many had lost their boots
But limped on, blood-shod. All went lame; all blind;
Drunk with fatigue; deaf even to the hoots
Owen uses the onomatopoeic verb “trudge” to  emphasise the difficulty of marching through mud. 
 
 The “distant rest” is ambiguous, referring to their camp, but also oblivion — a reference to the likely deaths of these soldiers which, no doubt would be a relief from the misery of the trenches.