I think this is the song about soldiers in war. Someone was in war, and they are describing what it was like and how he will never forget the bodies, remembering being commanded "March on, March on", shooting whatever feels like a threat, knowing that when you shoot them you shoot to kill and they are gone forever, and basically just regretting all of it and feeling guilty wondering how many of them died for nothing and how no one may remember them.
I think this is the song about soldiers in war. Someone was in war, and they are describing what it was like and how he will never forget the bodies, remembering being commanded "March on, March on", shooting whatever feels like a threat, knowing that when you shoot them you shoot to kill and they are gone forever, and basically just regretting all of it and feeling guilty wondering how many of them died for nothing and how no one may remember them.