It's just another day on the battlefields of World War I . As our speaker lets us know right away, however, "normal" isn't a word that has any meaning for the soldiers anymore. They're all mentally and physically ravaged by the exertions of battle.
And then it gets worse. Just as the men are heading home for the night, gas shells drop beside them. The soldiers scramble for their gas masks in a frantic attempt to save their own lives. Unfortunately, they don't all get to their masks in time. Our speaker watches as a member of his crew chokes and staggers in the toxic fumes, unable to save him from an excruciating certain death.
Now fast-forward. It's some time after the battle, but our speaker just can't get the sight of his dying comrade out of his head. The soldier's image is everywhere: in the speaker's thoughts, in his dreams, in his poetry. Worst of all, our speaker can't do anything to help the dying soldier.
Bitterly, the speaker finally addresses the people at home who rally around the youth of England, and urge them to fight for personal glory and national honor. He wonders how they can continue to call for war. If they could only witness the physical agony war creates – or even experience the emotional trauma that the speaker's going through now – the speaker thinks they might change their views. In the speaker's mind, there's noting glorious or honorable about death. Or, for that matter, war itself.