There are three time periods referred to in the poem. You could ask pupils to shade in a different colour references to; 1. His youth, before he joined the army 2. When he was injured 3. The present, disabled and in hospital. Quite often these are used as contrasts - the smear of blood on his leg after football compared with the 'purple' blood spurting on the battlefield, or feeling how slim girls' waists were compared with now, when the women touch him like some queer disease. Alternatively, split the poem up yourself and ask pupils to sort the lines into three piles in the same way, then find pairs that deal with the same theme. I think it is important that the poem ends with a return to the reality of the present.