War-Dulce et Decorum Est by Wilfred Owen

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
Of tired, outstripped Five-Nines that dropped behind.

Gas! Gas! Quick, boys!- An ecstacy of fumbling,
Fitting the clumsy helmets just in time;
 But someone still was yelling out and stumbling
And flound'ring like a man in a fire or lime..
Dim, through the misty panes and thick green light,
As under a green sea, I saw him drowning.

In all my dreams, before my helpless sight,
He plunges at me, guttering, choking, drowning.

If in some smothering dreams you too could pace
Behind the wagon that we flung him in,
And watch the white eyes writhing in his face,
His hanging face, like a devils sick of sin;
If you could hear, at every jolt, the blood
Come gargling from the froth corrupted lungs,
Obscene as cancer, bitter as cud
Of vile, incurable sores on innocent tongues,-
My friend, you would not tell with such high zest
To the children ardent for some desperate glory,
The old Lie: Dulce et decorum est
Pro patria mori

The horror of war as can only be described by someone witnessing it.  These words deny the romantic stories told by those encouraging young men to fight in a war and sacrifice one's only life. Owen starts off by describing in painful detail the discomforts of the mission, "cursing through sludge", men "had lost their boots" but continued to march for the promise rest somewhere in the near future.  The promise was soon not certain as they were attacked and a gas bomb was dropped, panic ensued.  The writer describes what he witnesses as one of the men cannot get his mask on quickly enough and suffocates as he watches helplessly. He recognizes in this moment the lie about the honor of giving you life for your country. It's ugly and vile, he looks at the man's blank stare and hears the sounds in his lungs as the gas continues to poison them after his death. He decides that it is not, "sweet and fitting to die for one's country."