Here Owen introduces the caesura, a break or pause in a line. Owen deploys the medial (meaning 'in the middle') caesura, a use derived from Old English or Anglo-Saxon poetry (c. 500 CE to 1100 CE).

According to Paul Fussell, in Poetic Meter and Poetic Form, "Caesuras, which are often marked with punctuation, can be said to correspond to breath pauses between musical phrases; in verse, their slight interruption of the propulsive metrical pattern can provide a kind of expressive counterpoint or opposition..." (p. 23)

In this, and the next two lines, Owen deploys the caesura to pile detail upon detail, each of the six short phrases a sharper and sharper declination into deprivation. The first three describe the men's physical appearance, the last three a total destruction of physical propulsion and perception: lame, blind, drunk and deaf. This structure, an accumulation of specific details, rather than a shaped narrative, also recalls Anglo-Saxon poetry. (p. 63)

It is as if the speaker is deliberately smashing the lyrical music of the full line to catalogue the death of the body, sense by sense. Yet the regularity of the placing of the caesura, in the middle of each line, also drives home the formality of the men's marching, the plodding regularity of left after right, left after right.