It's obvious straightaway that Wilfred Owen wrote "Dulce et Decorum est" to deglamourise war. When the First World War broke out the youth of Britain very enthusiastically volunteered to join the army. They were inspired by the ideals of patriotism, glory and honour and martyrdom. But once they set foot on European soil and directly engaged with the enemy, the horrors of war literally shell shocked them. The thing they dreaded most was death by the odourless and colourless 'mustard gas.' Although they were provided gas masks the fatal effects of the gas were subtle and swift-millions died even before they could put on their masks.
The opening stanza describes the battle weary soldiers "drunk with fatigue" returning,
"towards our distant rest began to trudge.
Men marched asleep."
just before a gas attack.
The rhyme scheme of the first stanza is ababcdcd. Except for 'behind' in the last line of the first stanza which has two syllables all the other rhyming words are single syllables.
The rhyme scheme of any poem serves two important purposes:
1. Organisation of content: In the first four lines, the poet ignominiously compares the weary soldiers to beggars returning at the end of the day with their sacks full and bent double. The next four lines describes how tired they were. They were so exhausted that they marched in their sleep and were completely oblivious to the sound of the deadly gas shells dropping.
2. Euphony: The sound of the rhyming words echoes aptly the horrors of the war. Each rhyming word harshly emphasizes the savagery of the war and the ghastly conditions of the actual battlefield, most strikingly the rhyming words 'trudge' and 'sludge:' The rains in Europe often converted the battle fields into huge swamps in which many soldiers drowned and fighting in such conditions was next to impossible.