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Battlefield Mercy: Unpacking the Nature and Significance of Supererogation in War

  • Neil C. Renic


Debates over how best to ensure appropriate conduct in battle typically draw a binary distinction between rule compliance and rule violation. This framing is problematic, excluding a critical third element of battlefield conduct, supererogation—that is, positive acts that go beyond what is demanded by the explicit rules of war. This article investigates this moral category of action; specifically, situations in which combatants refrain from taking the life of an enemy despite their moral and legal license to do so. It first considers the moral tension between the duty of combatants to kill and battlefield mercy, and goes on to explore the factors that motivate the latter. The article then shifts to consider the significance of supererogation to the ongoing efforts to moderate the conduct of contemporary war. As the article illustrates, supererogatory restraint is constituted by values that when cultivated also incentivize adherence to the more explicit rules and standards of the battlefield. This is demonstrated through analysis of the conduct of Western special forces. The concept of supererogation is of further use when evaluating the origins and implications of “moral injury.” This is verified empirically in the context of armed unmanned aerial vehicles.



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I would like to thank Andrew Dougall, Andrew Flescher, Josie Hornung, Sebastian Kaempf, Jacinta O'Hagan, Sarah Percy, Megan Price, Melinda Rankin, Christian Reus-Smit, Ryan Smith, Stan Steindl, Mark Timmons, and the four anonymous reviewers of this article for their insightful comments.



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2 See, for example, Bassiouni, M. Cherif, “The New Wars and the Crisis of Compliance with the Law of Armed Conflict by Non-State Actors,” Journal of Criminal Law and Criminology 98, no. 3 (March 2008), pp. 711810; Búzás, Zoltán I., “Evading International Law: How Agents Comply with the Letter of the Law but Violate Its Purpose,” European Journal of International Relations 23, no. 4 (November 2016), pp. 857–83; Cassese, Antonio, “Current Challenges to International Humanitarian Law,” in Clapham, Andrew and Gaeta, Paola, eds., The Oxford Handbook of International Law in Armed Conflict (Oxford: Oxford University Press, 2014); and Cogan, Jacob Katz, “Noncompliance and the International Rule of Law,” Yale Journal of International Law 31 (2004), pp. 189210.

3 Horgan, Terry and Timmons, Mark, “Untying the Knot from the Inside Out: Reflections on the ‘Paradox’ of Supererogation,” Social Philosophy and Policy 27, no. 2 (2010), p. 32.

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5 Lussu, Emilio, quoted in Walzer, Michael, Just and Unjust Wars: A Moral Argument with Historical Illustrations (New York: Basic Books, 2006), p. 141.

6 Ibid., p. 143.

7 Dinstein, Yoram, “The System of Status Groups in International Humanitarian Law,” in von Heinegg, Wolff Heintschel and Epping, Volker, eds., International Humanitarian Law Facing New Challenges: Symposium in the Honour of Knut Ipsen (Berlin: Springer, 2007), p. 144.

8 Army Doctrine Publication, cited in Taylor, Claire, Armed Forces Covenant (London: House of Commons, June 9, 2011), p. 2 (emphasis added),

9 Uniform Code of Military Justice, 10 U.S.C. §§ 801–940 (1964),

10 Emilio Lussu, quoted in Walzer, Just and Unjust Wars, p. 142.

11 Hare, Richard Mervyn, Moral Thinking: Its Levels, Method, and Point (Oxford: Oxford University Press, 1981); and Heyd, David, Supererogation: Its Status in Ethical Theory (Cambridge, U.K.: Cambridge University Press, 1982).

12 Kamm, Frances Myrna, “Supererogation and Obligation,” Journal of Philosophy 82, no. 3 (March 1985), p. 118.

13 Ibid., pp. 119–20.

14 Eisenberg, Theodore and Garvey, Stephen P., “The Merciful Capital Juror,” Ohio State Journal of Criminal Law 2, no. 1 (Fall 2004), p. 165; and Rainbolt, George, “Mercy: In Defence of Caprice,” Noûs 31, no. 2 (June 1997), pp. 235–36.

15 Benbaji, Yitzhak, “A Defense of the Traditional War Convention,” Ethics 118, no. 3 (April 2008), p. 466; and Gross, Michael L., “Assassination and Targeted Killing: Law Enforcement, Execution or Self-Defence?,” Journal of Applied Philosophy 23, no. 3 (August 2006), p. 329.

16 Morkevičius, Valerie, “Tin Men: Ethics, Cybernetics and the Importance of Soul,” Journal of Military Ethics 13, no. 1 (May 2014), pp. 57.

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18 Dinstein, Yoram, “Legal and Ethical Lessons of NATO's Kosovo Campaign,” in Wall, Andru E., ed., International Law Studies 78 (2002), p. 153.

19 Glover, Michael, Humanity: A Moral History of the Twentieth Century (London: Pimlico, 2001), p. 53.

20 Quoted in ibid., p. 53.

21 Eisenberg and Garvey, “Merciful Capital Juror,” p. 169.

22 Lieber, Francis, Manual of Political Ethics, Part 2: Political Ethics Proper (for the use of colleges and students in law) (Boston, USA: Charles C Little and James Brown, 1876), p. 660.

23 This ambiguity can also be found at the level of jus ad bellum in the disagreement over what exactly constitutes an “imminent threat.” The United States is among those that have sought to reinterpret and expand the concept of imminence to include less immediate and pressing threats. Critics fear that such efforts stretch the concept “beyond recognition.” See Michael W. Lewis, “Elongated Imminence and Operational Realities,” Opinio Juris, January 29, 2013,; and U.S. Department of Justice, “Lawfulness of a Lethal Operation Directed against a U.S. Citizen Who Is a Senior Operational Leader of Al-Qa'ida or an Associated Force” (white paper, U.S. Department of Justice, November 8, 2011),

24 Lamm, Claus, Batson, C. Daniel, and Decety, Jean, “The Neural Substrate of Human Empathy: Effects of Perspective-Taking and Cognitive Appraisal,” Journal of Cognitive Neuroscience 19, no. 1 (February 2007), p. 42.

25 Thompson, Evan, Mind in Life: Biology, Phenomenology and the Sciences of the Mind (Cambridge, Mass.: Belknap Press of Harvard University Press, 2007), p. 388.

26 Gray, Jesse Glenn, The Warriors: Reflections on Men in Battle (Lincoln: University of Nebraska Press, 1998), p. 159.

27 Grossman, Dave, On Killing: The Psychological Cost of Learning to Kill in War and Society (New York: Back Bay Books, 2009).

28 Crozier, F. P., A Brass Hat in No Man's Land (London: C. Chivers, 1950), p. 42.

29 Dara Kay Cohen explores the process of combatant socialization in relation to the war crime of gang rape. Multiple perpetrator rape, Cohen argues, may function as a tool for armed group cohesion, communicating norms of virility, masculinity, brutality, and loyalty. See Cohen, Dara Kay, “The Ties that Bind: How Armed Groups Use Violence to Socialize Fighters,” Journal of Peace Research 54, no. 5 (September 2017), p. 701.

30 Jünger, Ernst, Storm of Steel, trans. Hofmann, Michael (New York: Penguin Books, 2004), p. 234.

31 Bloom, Paul, Against Empathy: The Case for Rational Compassion (London: Bodley Head, 2016).

32 Bloche, M. Gregg and Marks, Jonathan H., “When Doctors Go to War,” New England Journal of Medicine 352, no. 1 (January 2005), pp. 36.

33 Quoted in Glover, Humanity, pp. 54–55.

34 Bourke, Joanna, An Intimate History of Killing: Face-to-Face Killing in Twentieth-Century Warfare (London: Granta Books, 1999).

35 Babchenko, Arkady, One Soldier's War in Chechnya (New York: Routledge, 2007), p. x.

36 Arendt, Hannah, “Personal Responsibility under Dictatorship,” Listener 72, no. 1845 (1964), p. 44 (emphasis in original).

37 Ibid., p. 44.

38 Morkevičius, “Tin Men,” p. 4.

39 Gray, The Warriors, p. 186.

40 Waldman, Thomas, “Vicarious Warfare: The Counterproductive Consequences of Modern American Military Practice,” Contemporary Security Policy 39, no. 2 (April 2018), pp. 192–95. Waldman also highlights a third approach—delegation—which involves shifting the burden of risk to proxy forces, including private military and security companies, irregular militias, and other indigenous forces.

41 Enemark, Christian, “Drones, Risk, and Moral Injury,” Critical Military Studies 5, no. 2 (October 2017), p. 155.

42 Ministry of Defence, quoted in Ben Quinn, “MoD Study Sets Out How to Sell Wars to the Public,” Guardian, September 26, 2013,

43 Nick Turse, “US Special Operations Forces Are in More Countries than You Can Imagine,” Nation, January 20, 2015,

44 William McRaven, quoted in Dan Lamothe, “Retiring Top Navy SEAL: ‘We Are in the Golden Age of Special Operations,’” Washington Post, August 29, 2014,

45 Moran, Jon, “Time to Move Out of the Shadows? Special Operations Forces and Accountability in Counter-Terrorism and Counter-Insurgency Operations,” University of New South Wales Law Journal 39, no. 3 (2016), pp. 1241–42.

46 Richard Norton-Taylor, “Talking about Taliban Killers Is Taboo in the UK,” Guardian, December 7, 2011,

47 “Australian Special Forces Veteran Breaks Silence on ‘Insidious, Infectious’ Culture,” ABC (Australian Broadcasting Corporation), July 9, 2017,

48 Masters, Chris, No Front Line: Australian Special Forces at War in Afghanistan (Sydney: Allen & Unwin, 2017), p. 490.

49 Chris Masters and Nick McKenzie, “Standing Up, Not Shooting: The ‘Compassionate Psychopaths’ of the SAS,” Sydney Morning Herald, August 4, 2018,

50 Daniel Muñoz-Rojas, Jean-Jacques Frésard, and International Committee of the Red Cross, The Roots of Behaviour in War: Understanding and Preventing IHL Violations (Geneva: International Committee of the Red Cross, 2005), pp. 196–97.

51 International Committee of the Red Cross, The Roots of Restraint in War (Geneva: International Committee of the Red Cross, 2018), p. 9.

52 Ibid., pp. 32–33.

53 Renic, Neil C., “Justified Killing in an Age of Radically Asymmetric Warfare,” European Journal of International Relations 25, no. 2 (June 2019), pp. 408–30.

54 Keegan, John, “If You Won't, We Won't: Honour and the Decencies of Battle,” Times Literary Supplement, no. 4834 (November 24, 1995), p. 11.

55 Moran, “Time to Move Out of the Shadows?,” p. 1240.

56 Heyd, Supererogation, p. 10.

57 Morison, Elting E., Men, Machines, and Modern Times (Cambridge, Mass.: MIT Press, 1966), p. 34.

58 Manion, Jennifer C., “The Moral Relevance of Shame,” American Philosophical Quarterly 39, no. 1 (January 2002), p. 77.

59 Diane Silver, “Beyond PTSD: Soldiers Have Injured Souls,” Pacific Standard, January 22, 2015,

60 Shira Maguen and Brett Litz, “Moral Injury in the Context of War,” National Center for PTSD, n.d.,

61 “What Is Moral Injury,” Moral Injury Project, Syracuse University, n.d.,

62 Jesse Kirkpatrick, “Military Drone Operators Risk a Serious Injury: And It's One You Might Not Expect,” Slate, January 26, 2016,; Maguen, Shira and Litz, Brett, “Moral Injury in Veterans of War,” PTSD Research Quarterly 23, no. 1 (January 2012), p. 1; and Maguen and Litz, “Moral Injury in the Context of War.”

63 Frankfurt, Sheila B., Frazier, Patricia, and Engdahl, Brian, “Indirect Relations between Transgressive Acts and General Combat Exposure and Moral Injury,” Military Medicine 182, nos. 11/12 (November/December 2017), p. 1950.

64 Drescher, Kent D., Foy, David W., Kelly, Caroline, Leshner, Anna, Schutz, Kerrie, and Litz, Brett, “An Exploration of the Viability and Usefulness of the Construct of Moral Injury in War Veterans,” Traumatology 17, no.1 (March 2011), pp. 2, 813.

65 Wayne Chappelle, quoted in Eyal Press, “The Wounds of the Drone Warrior,” New York Times, June 13, 2018, The definition of moral injury remains contested and has yet to be fully accepted by the military and psychological community.

66 David Wood, “The Grunts: Damned If They Kill, Damned If They Don't,” Huffington Post, March 18, 2014,

67 “Drones are Ethical and Effective,” YouTube video, 8:42, from a speech given by Kenneth Anderson, posted by Oxford Union, May 3, 2013,; “The Efficacy and Ethics of U.S. Counterterrorism Strategy,” webcast, 1:09, from a speech given by John Brennan at the Woodrow Wilson Center, May 1, 2012,; Brunstetter, Daniel and Braun, Megan, “The Implications of Drones on the Just War Tradition,” Ethics and International Affairs 25, no. 3 (Fall 2011), pp. 337–58, 348; Fricker, Matthew, Plaw, Avery, and Williams, Brian Glyn, “New Light on the Accuracy of the CIA's Predator Drone Campaign in Pakistan,” Terrorism Monitor 8, no. 41 (November 2010), p. 8; and Strawser, Bradley Jay, “Moral Predators: The Duty to Employ Uninhabited Aerial Vehicles,” Journal of Military Ethics 9, no. 4 (2010), pp. 342–68.

68 Rise of the Drones: Unmanned Systems and the Future of War, 111th Cong., 2nd sess. 201 (March 23, 2010) (written testimony of Kenneth Anderson, Professor of Law, American University Washington College of Law), p. 12,

69 Micah Zenko and Amelia Mae Wolf, “Drones Kill More Civilians than Pilots Do,” Foreign Policy, April 25, 2016,

70 United Nations General Assembly, “Report of the Special Rapporteur on Extrajudicial, Summary or Arbitrary Executions, Philip Alston,” A/HRC/14/24/Add.6, May 28, 2010, p. 25,; Claire Finkelstein, “Targeted Killing as Pre-Emptive Action,” in Claire Finkelstein, Jens David Ohlin, and Andrew Altman, eds., Targeted Killings: Law and Morality in an Asymmetrical World (Oxford: Oxford University Press, 2011), p. 174; Chris Cole, Convenient Killing: Armed Drones and the “PlayStation” Mentality (Oxford: Fellowship of Reconciliation, 2010); and Peter Olsthoorn, Military Ethics and Virtues: An Interdisciplinary Approach for the 21st Century (New York: Routledge, 2011), p. 126.

71 Williams, John, “Distant Intimacy: Space, Drones, and Just War,” Ethics and International Affairs 29, no. 1 (March 2015), p. 93.

72 Enemark, “Drones, Risk, and Moral Injury,” p. 11.

73 Lee, Peter, Reaper Force: Inside Britain's Drone Wars (London: John Blake, 2018), pp. 3839.

74 Jeff Bright, quoted in Press, “Wounds of the Drone Warrior.”

75 Brandon Bryant, quoted in Ed Pilkington, “Life as a Drone Operator: ‘Ever Step on Ants and Never Give It Another Thought?,” Guardian, November 19, 2015,

76 Toby, quoted in Lee, Reaper Force, p. 224.

77 Toby, quoted in ibid., p. 224.

78 Hernando Ortega, quoted in Elisabeth Bumiller, “A Day Job Waiting for a Kill Shot a World Away,” New York Times, July 29, 2012,

79 Lee, Reaper Force, pp. 278–79. British Reaper operators most often express concern in one of two ways: first, that they might accidently kill noncombatants; and second, that they might miss (or be prevented from taking) a shot against an individual who would then go on to commit further violence.

80 Quoted in Press, “Wounds of the Drone Warrior.”

81 Enemark, Christian, Armed Drones and the Ethics of War: Military Virtue in a Post-Heroic Age (London: Routledge, 2013); French, Shannon E., Sisk, Victoria, and Bass, Caroline, “Drones, Honor, and Fragmented Sovereignty: The Impact of New and Emerging Technology on the Warrior's Code,” in Brunstetter, Daniel R. and Holeindre, Jean-Vincent, eds., The Ethics of War and Peace Revisited: Moral Challenges in an Era of Contested and Fragmented Sovereignty (Washington, D.C.: Georgetown University Press, 2018); Kirkpatrick, Jesse, “Drones and the Martial Virtue Courage,” Journal of Military Ethics 14, no. 3–4 (October 2015), pp. 202–19; Renic, Neil C., “UAVs and the End of Heroism? Historicising the Ethical Challenge of Asymmetric Violence,” Journal of Military Ethics 17, no. 4 (March 2019), pp. 188–97; Sparrow, Robert, “War without Virtue?,” in Strawser, Bradley Jay, ed., Killing by Remote Control: The Ethics of an Unmanned Military (Oxford: Oxford University Press, 2013), pp. 9899; and Tonkens, Ryan, “The Case against Robotic Warfare: A Response to Arkin,” Journal of Military Ethics 11, no. 2 (August 2012), pp. 149–68.

82 One article that does address this issue is Enemark, “Drones, Risk, and Moral Injury.”

83 French, Sisk, and Bass, “Drones, Honor, and Fragmented Sovereignty,” pp. 213–15.

84 Lee, Reaper Force, p. 95; and Matthew Power, “Confessions of a Drone Warrior,” GQ, October 23, 2013,

85 Quoted in Bourke, An Intimate History of Killing, p. 3.

* I would like to thank Andrew Dougall, Andrew Flescher, Josie Hornung, Sebastian Kaempf, Jacinta O'Hagan, Sarah Percy, Megan Price, Melinda Rankin, Christian Reus-Smit, Ryan Smith, Stan Steindl, Mark Timmons, and the four anonymous reviewers of this article for their insightful comments.



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