The speaker says he sees God in the cracked mud on the wretches' faces. He sees that war makes them more glorious than their lineage, and their laughs are more mirthful than a child's. It felt good to laugh there, when "death is absurd, and life absurder". They felt no remorse when they killed people.
The speaker says he left his fear behind him, as "dead as my platoon", and his spirit soars up away from the battlefield where hopes lie strewn about. He sees faces lifted in worship and praise even though they used to curse him.
He has made fellowships at war, but these are not the fellowships from old songs. Love is not "fair lips" and sweet eyes and ribbons, but thick wires bound around arms dripping blood knit together with the rifle's case. There is beauty in the oaths he hears and music in the quietness of duty, and peace even when the artillery is shelling.
However, unless you (reader) are in hell with these men, whose world is a trembling flare and for whom heaven is only a "highway for a shell", you do not hear their mirth and cannot know if they are content. The men deserve your tears, but you are "not worth their merriment".
The poem's Latin title means "In Defense of My Poetry." The poem is said to have been a response to Robert Graves's letter to Owen, which recommended that the young soldier poet "cheer up" and write more optimistic poetry. Not long after reading the letter, Owen wrote to his mother on October 31st, 1918, extolling the band of friends he had made: "Of this I am certain, you could not be visited by a band of friends half so fine as surround me here." These were the last words of his last letter.
Indeed, Owen's expression of the fellowship among soldiers is one of the salient aspects of the poem. He describes the mud on his companions' faces lovingly, and revels in their deep laughs. That laughter is one of the things that somewhat mitigates the difficulties of war. He sees his fellow soldiers' faces, "seraphic" and lifted up "with passion of oblation"; their bonds are clearly deep. He criticizes people who think that love is filled with the trappings of romance and sentiment, and says that for him he sees real love in the grime and viscera of the battlefield. It is not a ribbon but "war's hard wire" that ties the bond of love. He also discusses how he finds beauty in their experiences, insinuating that those who aren't soldiers could not understand.
Beneath the expression of friendship and fellowship lies a bit more perturbing element. The men are laughing in the trenches, and have come to feel that death and life are absurd. Furthermore, they are desensitized to killing – "For power was on us as we slashed bones bare / Not to feel sickness or remorse of murder". The speaker can no longer feel fear or hope, but to claim that soldiers feel no fear does not ring true in light of Owen's other writing. Several of his letters speak of his agony, his disillusionment, and his apprehension. However, a letter addressed to his brother in May 1917 spoke of how exultant he was to have survived an artillery barrage. Owen's thoughts on the subject are, then, contradictory.
The poem is full of contradictions. The soldiers are able to be real and human with each other, but set aside that humanity when killing the enemy. They are angelic in their fellowship but are killers. They are dirty and bloody but are depicted as saintly even under the muck. War is hell, but can bring with it some earthy joys.
The final theme of the poem is that the outside world cannot understand what soldiers experience. This is a direct response to Graves's ignorant comment. Owen specifically addresses the world removed from war – the "you" of the last stanza – and says that unless you are in this hell with the soldiers, you do not understand their situation. You should cry for them, but you should not think they will waste any time thinking of you and laughing for you.