It seems you inwardly grin as you pass
Strong eyes, fine limbs, haughty athletes,
Less chanced than you for life,
Bonds to the whims of murder,
Sprawled in the bowels of the earth,
The torn fields of France.
What do you see in our eyes
At the shrieking iron and flame
Hurled through still heavens?
What quaver—what heart aghast?
Poppies whose roots are in man's veins
Drop, and are ever dropping;
But mine in my ear is safe—
Just a little white with the dust.
In a quiet, understated conclusion Rosenberg takes us back to the earlier line when he ‘stuck’ the poppy behind his ear. He claims that his poppy is safe and so is he. 
 Note the dash that ends the line, forming a thoughtful  caesura , a pause in which the reader knows that he is either fooling himself or being ironic.
Break of Day in the Trenches