The idea that warfare ought to be subject to restraint is probably as old as war itself. The restraints morality and law place on war fall under two heads: those concerning resort to war (
jus ad bellum
) and those concerning the ways war is fought (
jus in bello
). One of the rules comprising
jus in bello
– on most accounts, its centerpiece – is that of discrimination (or, in legal parlance, distinction). It enjoins us to discriminate between legitimate and illegitimate targets in war and to restrict our attacks to the former. That means, roughly, that our acts of war may be directed only at enemy soldiers or combatants and military facilities, and that we must not attack civilians or noncombatants. Civilians (noncombatants) enjoy immunity against deliberately inflicted harm to life, limb, or property.