"Oops" we thought we were killing the enemies of the people.
"Oops" we thought all them were Viet Cong and could have killed us
"Oops" we were over-stressed, tired and and upset about our soldiers being tortured so we went all hog wild on them
That's really about it, believe it or not.
If you go into a field and there's a bunch of armed VC villagers who start shooting back at your then an air strike is militarily justified, until the defense ceases.
If you go into a field and there's a bunch of women and children (unarmed!, and I hate that I have to mention that...) then there is no valid military purpose to an air strike.
Now, from just the air if you have good intelligence that there is a grouping of enemy soldiers at a concentration point then even under Geneva that might be all the valid military purpose you need to approve dropping bombs at that location, even at risk of collateral damage.
A war crime would be a military action taken out of proportion to the valid military purpose that might justify it. E.g. if it was known that there were lots of civilians and just a few fighters at that location. Or if you shot a soldier in the act of surrendering (note how rarely U.S. soldiers are afforded even the opportunity to surrender in the few times Taliban managed to encircle a U.S. squad).
I, too, wish that we lived in that wonderful world where civilians are not used as human shields and that all intel is perfect (God knows NSA is trying!) but that's not the world we live in. The world we live in has both Geneva Conventions and the precedent of Nuremburg and does not simply define "war crime" as "things that happen which we don't like".
If you try to redefine "war crime" we'd simply have to come up with yet another definition to mean what it's supposed to mean for things like war crimes tribunals.
You were asked, if you accept "oops" as a valid excuse, is it possible to successfully prosecute any war crime? Can you think of any examples of war crimes where "oops" could not be used as a defense?
"If you go into a field and there's a bunch of women and children (unarmed!, and I hate that I have to mention that...) then there is no valid military purpose to an air strike."
If you accept "oops" as an excuse, then guess what? That air strike was an "oops".
Pretty sure there's something in there about destroying entire village(s) filled with people.
Destroying a civilian building being used as a military facility, on the other hand, is not a war crime, except if there was no valid military purpose to the strike or the strike was not proportional to the military value that might be gained (e.g. it would never be acceptable post-Geneva to kill 1000 civilians just to destroy an enemy soldier). That was one of the justifications the Germans used to sink Lusitania (which despite American and British protestations, it appears the Germans had actually been right in retrospect).
