Picky and not terribly relevant tangent: the concept of war crimes is far from new. The Middle Ages developed a pretty sophisticated Just War theory, which dealt with not only who could declare a war and on what grounds (jus ad bellum), but also what they could and couldn’t do during it (jus in bello). For example, non-combatants, and especially clergy, were theoretically off-limits. Jurisdiction was universal: any potentate could convene a court-martial against any alleged offender who fell into their hands.
Of course, this was the Middle Ages, and enforcement was patchy: plus there were loopholes a-plenty. All bets were off during a siege, for example: sieges were almost as dangerous to the besiegers as the besieged (dysentery, anyone?), so if you were compelled to storm a castle or town (because the defenders refused to surrender) you were entitled to kill everyone inside it pour encourager les autres. And sheltering in a church seems logical (it was probably the largest and maybe the only stone building in the village, plus clerical immunity) – except that to facilitate this role, many churches had battlements, which in the eyes of attackers turned them from a church into a fortification and hence a legitimate target.
But the war crime is not, in itself, a new idea.
