Just war theory is a difficult, even paradoxical, philosophical topic. It is not just that warfare involves large-scale, organised, deliberate killing, and hence might seem the very paradigm of immorality. The just war tradition sharply divorces the question of whether or not it is permissible to resort to war – the question of jus ad bellum – from the question of how and against whom one may inflict harm once at war – the question of jus in bello. As Michael Walzer notes,1 this separation of jus in bello from jus ad bellum means that we can meaningfully talk of an unjust war being fought justly, and vice versa: soldiers defending against aggression might nevertheless be criminals for the way in which they do it; while soldiers prosecuting an aggressive war, provided they fight it in the right way, are without culpability. This paper will draw upon the morality of individual self-defence to explain certain important features of the traditional jus in bello: the permissibility of killing, even by soldiers who lack justice on their side; the principles that govern surrender and the taking of prisoners of war; and the principle of discrimination between soldiers and civilians. Our explanation will not leave all aspects of the jus in bello undisturbed: it has consequences that are revisionary in at least some respects, this being the upshot of trying to explain the jus in bello in individualist terms. Partly because of such consequences, approaching the morality of war in individualist terms is neither straightforward nor uncontroversial.2 But we are prepared to accept..