(Irony)
The irony is that the way they are killing the louse is the way they are killing people.
p 86-88 "But what will really happen when we go back?"... We believe in such things no longer we believe in the war.
(Destructivness of war the lost generation)
They don't know what they will do after the war. Albert expresses it: "The war has ruined us for everything."
p 99-100 There are rumors of an offensive... To-night, two men are wounded by them
(Irony/Foreshadowing)
The Irony is that the English are getting more new guns while their own are worn out and bombarding their own lines.
p 103-104 During the day we loaf about... and what's more the blade often gets broken off.
(Irony, Understatement)
The irony is that when they are killing someone with their bayonet they may get killed by one themselves.
p 108-114 The night is unbearable... they did not count on so much resistance.
(Atmosphere, Irony)