Using a sing-song tone and cadences with rhyming couplets that end entirely on one-syllable words (boy/joy, glum/rum, know/go), the three-stanza poem tells a three-part story. Its nursery-rhyme tone flies in the face of its grim theme. 

The first stanza introduces us to an innocent young man who "grinned," "slept soundly" and "whistled with the lark." But despite its simple words and cadence, this stanza also uses language that makes us uneasy and foreshadows what is to come, such as "empty joy" and "lonesome dark." Words such as "empty" and "lonesome" are not those we associate with happiness. Even seemingly innocent terms like "grinned" and "slept soundly" foreshadow death and conjure images of a corpse and "grinning" skull. 

In the second stanza we are told quite bluntly that this young man, in the winter trenches of a World War I battlefield, "put a bullet through his brain." His surroundings are miserable, and he is without rum to dull his awareness. We learn in the last line of the stanza that nobody speaks of him again after his suicide.

In the third stanza, the poet addresses the people back home, calling them "smug faced" as they cheer parading soldiers. He implies that by treating war as heroic, ordinary people are complicit with the death and destruction it brings. He advises people to "sneak" home and pray they never have to experience the hell that young soldiers face. 

Sassoon uses the simplest possible language to make entirely clear how horrible war is. He is not trying to be subtle but seeks to make a point: pretending that war is a heroic business contributes to its horror because young men go in not knowing what to expect. Sassoon's title flies in the face of heroic war poems by stating starkly that his is about a suicide. Sassoon wants people to stop cheering on this terrible war and to remember how it has destroyed people. He wants people to remember not just the parading "heroes" but the forgotten casualties. 

In 'Suicide in the Trenches', Sigfried Sassoon uses three quatrains of iambic tetrameter, each consisting of two couplets, to give a jaunty cheerful rhythm that emphasizes the disconnect between the popular sense of war as thrilling and glorious and the grim realities of trench warfare.

The first stanza shows how a naive new soldier takes the popular enthusiasm for war into the trenches with him, and makes the reader start to feel cheerful about war. The second stanza marks a major transition to the reality of winter trench warfare and the boy`s suicide, in a twist that shocks the reader. The third stanza rebukes the reader for cheering young boys onto their deaths and invokes guilt.