The same man who, met in normal, everyday circumstances, might be a man you would have a drink with or loan a buck to, when met during wartime, is a man you kill. And there's no ideology in the poem. The two men facing each other on opposing sides do not have different opinions on vital issues, and are not fighting for any ideologies. They joined up because they needed money, or for some such trivial reason. They have nothing against each other. - See more at: http://www.enotes.com/homework-help/what-kind-litarary-device-were-used-man-he-killed-155023#sthash.fQBa85yq.dpuf