You know this one. 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 ecstasy of fumbling,
Fitting the clumsy helmets just in time;
But someone still was yelling out and stumbling,
And flound’ring like a man in 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 devil’s sick of sin;
If you could hear, at every jolt, the blood
Come gargling from the froth-corrupted lungs,
Obscene as cancer, bitter as the cud
Of vile, incurable sores on innocent tongues,
My friend, you would not tell with such high zest
To children ardent for some desperate glory,
The old Lie; Dulce et Decorum est
Pro patria mori.
So many boys, sent to their deaths for so little. And what’s more, we learned nothing from it—not in 1919, not in 1939 or 1945, not now. Certainly not now, in the last decadent days of the withering western empire.
Emily Rutherford 
And in answer to this I give you one of Sassoon’s lesser-known poems, The Dug-Out:
Why do you lie with your legs ungainly huddled,
And one arm bent across your sullen, cold,
Exhausted face? It hurts my heart to watch you,
Deep-shadowed from the candle’s guttering gold;
And you wonder why I shake you by the shoulder;
Drowsy, you mumble and sigh and turn your head…
You are too young to fall asleep for ever;
And when you sleep you remind me of the dead.
Wonderful. Thank you.
I know. Sassoon’s always such an angry, bitter man: his poetry’s often sharper and more acrid, with less of the gravitas and weight of the best of Owen, but this one has always held me by the heart and twisted – it’s a gesture filled with such pathos, the fear that strikes you when you’re caught by the sudden notion that your lover and your heart is dead, and you have to wake them up to know, made all the more poignant by the fact that Sassoon wrote this for the boys he knew in war…