The order to give the air strike was a war crime.

Another very obvious example was the My Lai massacre itself. It's really hard to find a valid military purpose for either carrying out the order to bayonet a child, or giving the order to kill a child.

But the fog of war is not as hazy on the ground. During WWII (which was admittedly a total war) you could drop all the bombs you wanted at a tank factory and still manage to hit the school a kilometer away. That wouldn't have made dropping the bombs a war crime by any stretch of the imagination though; the raid itself had a valid military purpose.