that’s a very manichean view. War ist all shades of (horrible) gray and you can have rules, a lot, none, everything is possible. Don’t know what you mean with “Geneva Convention notwithstanding” here, it’s exactly the kind of rules that _can_ exist in times of war – or be completely ignored on both sides.

It’s not because it’s war time that one should just resign, shrug and accept any atrocities. The less atrocities during war time, that more chances for a stable peace afterward.