 Just war theory has meaning only if we can explain why killing some combatants in war is allowed, but we are not thereby licensed to kill everyone in the enemy state. Here the competing forces of realism and pacifism are at their most compelling. It is unsurprising, therefore, that so much recent work has focused on this topic. We cannot do justice to all the arguments here, but will instead consider three kinds of response: all-out revisionist; moderate traditionalist; and all-out traditionalist.