What is really behind the atrocities committed by invading soldiers?
The real source is the old Adam. When invading soldiers are cut off from home and familiar surroundings, where no one knows them, the old Adam has free course. That explains pillaging and rape done seemingly without bother, and every unsaved person is capable of the same.
Les explains that the old Adam is really behind it. He illustrates from basic training: young men did things away from home they never did in their hometown, because “nobody knows me.” Even an unbeliever can be inhibited by surroundings, circumstances, parental influence, and community; but in a totally strange environment away from home, the old Adam has free course. That is exactly what happens when soldiers of an invading army pillage a community and rape women, seemingly without being bothered. It is the old Adam. Every person, before salvation, would have been capable of the same things, because that is where the human race is coming from. Paul is showing that the old Adam abounds with sin, but where sin abounds, God’s grace is always greater. Verse 21 then presents the old Adam reigning like a king, and grace reigning like a king—two alternatives.