Well Nazi Germany had a right to defend itself, too. Had it played by the rules there would have been no need for a Nuremburg.
Invading another country for a slight real or imagined ( a charge leveled against Germany) doesn’t seem to be war crime any more. Apparently lining people up and killing them, as Israel takes great pains NOT to do, is the bell whether of evil.
Decent war fighters would only do something like this ‘by accident’ or on grounds of humanitarianism, or in the heat of combat.