¹ See McMahan, J., ‘Innocence, Self-Defense and Killing in War’, Journal of Political Philosophy 2 (1994), pp. 193–221CrossRefGoogle Scholar; McMahan, J., ‘The Ethics of Killing in War’, Ethics 114 (2004), pp. 693–733CrossRefGoogle Scholar; McMahan, J., ‘War as Self-Defense’, Ethics & International Affairs 18 (2004), pp. 75–80CrossRefGoogle Scholar; McMahan, J., ‘Just Cause for War’, Ethics & International Affairs 19 (2005), pp. 1–21CrossRefGoogle Scholar; McMahan, J., ‘The Morality of War and the Law of War’, Just and Unjust Warriors, ed. Rodin, David and Shue, Henry (Oxford, 2008), pp. 19–43Google Scholar; McMahan, J., Killing in War (Oxford, 2009)CrossRefGoogle Scholar. For another and well-known attempt at reviving that classical account, see Rodin, D., War and Self-Defence (Oxford, 2002)CrossRefGoogle Scholar. For a useful collection of essays by proponents and opponents of McMahan's account, see Just and Unjust Warriors, ed. Rodin and Shue.

My main point of disagreement with McMahan pertains to the grounds upon which civilians who contribute to an unjust war are liable to attack. See Fabre, C., ‘Guns, Food, and Liability to Attack’, Ethics 120 (2009), 36–63CrossRefGoogle Scholar, to which McMahan responded on the Philosophy blog Peasoup, at <http://peasoup.typepad.com/peasoup/2010/01/ethics-discussions-at-pea-soup-c%C3%A9cile-fabres-guns-food-and-liability-to-attack-in-war-with-commentar.html#more> (accessed on 21 May 2010).

² To frag someone – typically a fellow soldier – is to injure or kill him or her with a grenade fragment. The term is widely used in the context of the Vietnam War. For cases of fragging during that war, see e.g. Moser, R. R., The New Winter Soldiers: GI and Veteran Dissent During the Vietnam Era (New Brunswick, NJ, 1996), pp. 48–50Google Scholar, and Westheider, J. E., The Vietnam War: American Soldiers’ Lives (Santa Barbara, 2007), pp. 187–8Google Scholar. Some authors claim that roughly 20 per cent of the officers who died during the Vietnam War did so as a result of fragging. See e.g. Regan, G., Backfire: A History of Friendly Fire from Ancient Warfare to the Present Day (London, 2002), p. 260Google Scholar. There are few documented cases of fragging in the British Army, but for one such case (which took place during the First World War), see Graves, R., Goodbye to All That (Harmondsworth, 1960)Google Scholar. See also Watson, A., Enduring the Great War: Combat, Morale and Collapse in the German and British Armies, 1914–1918 (Cambridge, 2008), p. 111CrossRefGoogle Scholar.

³ The US Army faced a similar situation earlier in the spring of 2009, when one of its soldiers opened fire on some of his comrades in a clinic for combat stress, killing five and injuring several. See The Washington Post, 12 May 2009.

⁴ On 26 February 1991, in one of the most widely reported incidents of the first Gulf War, American pilots attacked two British infantry vehicles in the Iraqi desert, killing nine British soldiers. For a book-length treatment of friendly fire, which also discusses this case, see Regan, Backfire.

⁵ Two points. First, although soldiers have sometimes killed commanding officers for the sake of fellow soldiers who were themselves subject to lethal threats at the hands of the former, I shall focus on self-defensive internecine killings: whether or not an agent has the right to kill an attacker in defence of a third party is a difficult issue which I lack the space to tackle in this article. Second, lack of space prevents me from scrutinizing cases where O exposes S to a lethal attack at the hands of the enemy – cases, in other words, where the presence of an intervening agency might be thought to weaken S's claim legitimately to kill O in self-defence.

⁶ It pays to note that according to art. 90 of the US Uniform Code of Military Justice, exercising violence against an officer and disobeying a lawful order are criminal offences which, if committed in wartime, are punishable by death. In Britain, the 2006 Armed Forces Act, which supersedes the 1955 Army Act, the 1955 Air Force Act and the 1957 Naval Discipline Act, similarly treats as criminal offences violent conduct towards an officer and refusal to obey a lawful order – offences for which soldiers are liable to imprisonment (for up to ten years). In both jurisdictions a soldier is under a duty to disobey an unlawful order. But neither law explicitly permits a soldier who is ordered at gunpoint to kill defenceless civilians to shoot his officer in self-defence or defence of others. Nor does either law readily lend itself to interpreting as unlawful a reckless or incompetent order.

⁷ See e.g. Rosen, D. M., Armies of the Young: Child Soldiers in War and Terrorism (New Brunswick, NJ, 2005)Google Scholar; Singer, P. W., Children at War (New York, 2005)Google Scholar. The case of Erdemovic is discussed by May, Larry in his War Crimes and Just War (Cambridge, 2007), pp. 285–8CrossRefGoogle Scholar.

⁸ Earlier versions of the article did not distinguish between those various senses of ‘threat’. I am grateful to Lazar for prompting me to do so here. McMahan is not alone in using ‘threat’ to mean ‘attack’. The confusion between those different senses of ‘threat’ in the literature on killing largely arises as a result of the standard labelling of innocent individuals whose mere presence or movements endanger our life as ‘innocent threats’. See, in addition to McMahan's own writings, Otsuka, M., ‘Killing the Innocent in Self-Defence’, Philosophy and Public Affairs 23 (1994), pp. 74–94CrossRefGoogle Scholar; Quong, J., ‘Killing in Self-Defence’, Ethics 119 (2009), pp. 507–37CrossRefGoogle Scholar.

⁹ See e.g. McMahan, ‘War as Self-Defense’. Note that I distinguish being permitted to do x (by which I mean that one is morally allowed to do so) and having the right to do x (by which I mean that third parties are under a duty not to interfere with our doing x). Analytically speaking, the claim that one may do x neither implies nor entails that one has the right to do so: for the latter claim to be true, one must show that third parties are under a duty to let us do that which we have a permission (or justification) to do. Conversely, one may lack permission for doing something which one nevertheless has the right to do – in other words, there can be such a thing as a right to do wrong. On the right to do wrong, see e.g. Waldron, J., ‘A Right to Do Wrong’, Ethics 92 (1981), pp. 21–39CrossRefGoogle Scholar. Note, incidentally, that being subject to a wrongful and serious attack is not a necessary condition for being permitted to kill one's attacker: if I could rescue millions of people from certain death by killing the man who is punching me in the stomach, I may do so (indeed, one might think that I am under a duty to do so). I am grateful to McMahan for pointing this out.

¹⁰ See Killing in War, pp. 183–4, and his ‘Preventive War and the Killing of the Innocent’, The Ethics of War – Shared Problems in Different Traditions, ed. D. Rodin and R. Sorabji (Aldershot, 2006), pp. 169–90.

¹¹ See McMahan, Killing in War, pp. 38–42, for this particular example. I say ‘at least against each other’ because this reading of the conflict between the strategic bomber and the civilians is compatible with both the view that third parties may take sides (in which case the bomber and the civilians lack a right against the world at large to kill each other) and the view that third parties must remain neutral (in which case the bomber and the civilians have the right against the world at large – though not against each other – to kill each other).

¹² McMahan, ‘The Morality of War and the Law of War’. I explore some of those complexities in relation to the liabilities of civilians in Fabre, ‘Guns, Food, and Liability to Attack’, sect. V.

¹³ See e.g. Shue, H., ‘Do We Need a ‘Morality of War’?’, Just and Unjust Warriors, ed. Rodin, and Shue, , pp. 87–111Google Scholar.

¹⁴ I am not aware that McMahan explicitly discusses this. But his pithy remarks on the First World War as an exercise in pointless butchery suggest that he would support that assertion. See Killing in War, p. 2.

¹⁵ The thought, here, is not that S is under a duty to obey O's order qua order; rather, the thought is that he is under a duty to obey that order because failing to do so would put others at risk. For the view that soldiers are (sometimes) under a duty to obey unjust orders, see Estlund, D., ‘On Following Orders in an Unjust War’, Journal of Political Philosophy 15 (2007), pp. 213–34CrossRefGoogle Scholar. McMahan rejects Estlund's argument in Killing in War, pp. 68–70.

¹⁶ See Coady, C. A. J., ‘Escaping from the Bomb: Immoral Deterrence and the Problem of Extrication’, Nuclear Deterrence and Moral Restraint, ed. Shue, H. (Cambridge, 1989), pp. 163–226CrossRefGoogle Scholar. Thus, it does not follow from the fact that one's war is unjust that one should end it immediately. For an interesting defence of this claim, see, Moellendorf, D., ‘Jus Ex Bello’, Journal of Political Philosophy 16 (2008), pp. 123–36CrossRefGoogle Scholar.

¹⁷ I am grateful to Zofia Stemplowska for bringing this issue to my attention.

¹⁸ For McMahan's explicit endorsement of the doctrine of acts and omissions, see his ‘Killing, Letting Die, and Withdrawing Aid’, Ethics 103 (1993), pp. 250–79. For some of his thoughts on soldiers’ contractual, professional duties, see his ‘The Just Distribution of Harm between Combatants and Noncombatants’, Philosophy and Public Affairs 38 (2010), pp. 342–79.

¹⁹ See Killing in War, pp. 48–9, for points in support of that view. Note that the view I defend here, as endorsed (I believe) by McMahan, is compatible with the claim that our obligations to those with whom we stand in a special relationship (such as a contractual or restitutive relationship) can sometimes override general obligations we may have to the world at large. For the view that S does have a special obligation to fellow citizens to kill SB, see Lazar, S., ‘Debate: Do Associative Duties Really Not Matter?’, Journal of Political Philosophy 17 (2009), pp. 90–101, at 101CrossRefGoogle Scholar.

²⁰ Both imperatives, of not exposing fellow soldiers to danger through one's refusal to fight, and the necessity of ‘holding the line’, are recurrent themes of writings on wartime military justice, mutiny and punishment. See works cited in n. 2.

²¹ Note that the wide instrumentality requirement is assumed only to be a necessary condition for permissible killing, and not a sufficient condition as well (in which latter case it would be too wide, since it would licence the killing of bystanders if such an act were to get soldiers to obey orders). I am grateful to Matt Kramer for this point.

²² See Crozier, F. P., The Men I Killed (London, 1937)Google Scholar. The French case is at the heart of Stanley Kubrick's compelling movie Paths of Glory. For similar cases during the American Civil War, see McPherson, J., For Cause and Comrades: Why Men Fought in the Civil War (Oxford, 1997), pp. 51ffGoogle Scholar.

²³ See Killing in War, pp. 170–3. The locus classicus for the distinction between eliminative and opportunistic agency is Quinn, W. S., ‘Actions, Intentions, and Consequences: The Doctrine of Double Effect’, Philosophy and Public Affairs 18 (1989), pp. 334–51Google ScholarPubMed. Quinn's focus is on the modes of agency by which one inflicts harms on others. For a thoughtful defence of the distinction in the context of killing, see Quong, ‘Killing in Self-Defence’, p. 525.

²⁴ Support for this view can be found in McMahan's discussion of the tactical bomber, in Killing in War, pp. 38–42. At p. 41, however, he writes: ‘[just combatants] could be liable either for attacking innocent civilians intentionally in the absence of a lesser-evil justification or for inflicting unnecessary or disproportionate harm on innocent civilians as a foreseeable side effect of action intended to destroy military targets’ (my emphasis). The italicized text suggests, by implication, that just combatants sometimes have a lesser-evil justification for targeting civilians.

²⁵ See e.g. Pedroncini, G., Les mutineries de 1917 (Paris, 1967)Google Scholar; Moser, The New Winter Soldiers; Westheider, The Vietnam War. Crozier claims, on the contrary, that ‘Men will not, as a rule, risk their lives unnecessarily unless they know that they will be shot down by their own officers if they fail to do or if they waver’ (Crozier, The Men I Killed, p. 68).

²⁶ The seeds for this article were planted in my mind by my former student Drew Flight, who wrote his Masters dissertation on fragging – though Flight does not avail himself of McMahan's account of the right to kill in war as a way to frame the issue. I am grateful to Seth Lazar, Alex Leveringhaus and Jonathan Quong for written comments on the first draft, as well as to participants at the 2010 UK Analytical Political and Legal Philosophy Conference and the Oxford Moral Philosophy Seminar, where I presented the second draft, for stimulating discussions. Jeff McMahan provided a raft of characteristically penetrating comments on the penultimate draft.