Physical pain and psychological trauma blur in this searing description of a World War I battleground. Caught in the memory of a gas-attack, the poem's speaker oscillates between the pain of the past (the actual experience of battle) and the pain of the present (he can't get the image of his dying comrade out of his head). As Owen argues, war is so painful that it becomes surreal.
By drawing readers directly into the action of battle, Owen's speaker manipulates us into assuming the anti-war stance that results from his own experiences of the war.