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Just War and Unjust Soldiers: American Public Opinion on the Moral Equality of Combatants

  • Scott D. Sagan and Benjamin A. Valentino


Traditional just war doctrine holds that political leaders are morally responsible for the decision to initiate war, while individual soldiers should be judged solely by their conduct in war. According to this view, soldiers fighting in an unjust war of aggression and soldiers on the opposing side seeking to defend their country are morally equal as long as each obeys the rules of combat. Revisionist scholars, however, maintain that soldiers who fight for an unjust cause bear at least some responsibility for advancing an immoral end, even if they otherwise fight ethically. This article examines the attitudes of the American public regarding the moral equality of combatants. Utilizing an original survey experiment, we find that the public's moral reasoning is generally more consistent with that of the revisionists than with traditional just war theory. Americans in our study judged soldiers who participate in unjust wars as less ethical than soldiers in just wars, even when their battlefield conduct is identical, and a large proportion supported harsh punishments for soldiers simply for participating in unjust wars. We also find, however, that much of the American public is willing to extend the moral license of just cause significantly further than revisionist scholars advocate: half of the Americans in our survey were willing to allow an unambiguous war crime—a massacre of innocent women and children—to go unpunished when the act was committed by soldiers fighting for a just cause. Our findings suggest that incorporation of revisionist principles into the laws of war would reinforce dangerous moral intuitions encouraging the killing of civilians.

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1 Walzer, Michael, Just and Unjust Wars: A Moral Argument with Historical Illustrations (New York: Basic Books, 1977), pp. 3438.

2 Frowe, Helen, Defensive Killing (Oxford: Oxford University Press, 2014); Lazar, Seth, “The Responsibility Dilemma for Killing in War: A Review Essay,” Philosophy & Public Affairs 38, no. 2 (Spring 2010), pp. 180213; Lazar, Seth, “Evaluating the Revisionist Critique of Just War Theory,” Daedalus 146, no. 1 (January 2017), pp. 113–24; Lazar, Seth, “Just War Theory: Revisionists vs. Traditionalists,” Annual Review of Political Science 20, no. 4 (2017), pp. 3754; McMahan, Jeff, Killing in War (Oxford: Oxford University Press, 2009); and Rodin, David, “The Moral Inequality of Soldiers: Why Jus in Bello Asymmetry Is Half Right,” in Rodin, David and Shue, Henry, eds., Just and Unjust Warriors: The Moral and Legal Status of Soldiers (New York: Oxford University Press, 2008), pp. 4468.

3 Barry, Christian and Christie, Lars, “The Moral Equality of Combatants,” in Lazar, Seth and Frowe, Helen, eds., The Oxford Handbook of Ethics of War (New York: Oxford University Press, 2018), pp. 339–57.

4 Walzer, Just and Unjust Wars, p. 39.

5 Ibid., p. 39.

6 McMahan, Killing in War, p. 104.

7 See Wallace, Geoffrey P. R., “Martial Law? Military Experience, International Law, and Support for Torture,” International Studies Quarterly 58, no. 3 (September 2014), pp. 501–14; Kreps, Sarah E. and Wallace, Geoffrey P. R., “International Law, Military Effectiveness, and Public Support for Drone Strikes,” Journal of Peace Research 53, no. 6 (November 2016), pp. 830–44; Press, Daryl G., Sagan, Scott D., and Valentino, Benjamin A., “Atomic Aversion: Experimental Evidence on Taboos, Traditions, and the Non-Use of Nuclear Weapons,” American Political Science Review 107, no. 1 (February 2013), pp. 188206; and Sagan, Scott D. and Valentino, Benjamin A., “Revisiting Hiroshima in Iran: What Americans Really Think about Using Nuclear Weapons and Killing Noncombatants,” International Security 42, no. 1 (Summer 2017), pp. 4179.

8 Ellner, Andrea, Robinson, Paul, and Whetham, David, eds., When Soldiers Say No: Selective Conscientious Objection in the Modern Military (New York: Routledge, 2014). Sherman, Nancy, The Untold War: Inside the Hearts, Minds, and Souls of Our Soldiers (New York: W. W. Norton, 2010). Nancy Sherman, who interviewed American military veterans about their views on the morality of war, found that many of them worried about the justice of the cause of the war in which they fought and whether the cause outweighed the death and destruction caused by the conflict.

9 Jeff McMahan, “Rethinking the ‘Just War,’ Part 2,” New York Times, November 12, 2012,

10 Audi, Robert, The Good in the Right: A Theory of Intuition and Intrinsic Value (Princeton, N.J.: Princeton University Press, 2005); Kauppinen, Antti, “Moral Intuition in Philosophy and Psychology,” in Clausen, Jens and Levy, Neil, eds., Handbook of Neuroethics 1 (Dordrecht, Netherlands: Springer, 2015), pp. 169–83; and McMahan, Jeff, “Moral Intuition,” in LaFollette, Hugh and Persson, Ingmar, eds., The Blackwell Guide to Ethical Theory (Oxford: Blackwell, 2000), pp. 103–20.

11 International Committee of the Red Cross (ICRC), Protocol Additional to the Geneva Conventions of 12 August 1949, and Relating to the Protection of Victims of International Armed Conflicts (Protocol I), June 8, 1977, 1125 UNTS 3, Preamble, p. 239.

12 Feldman, Yuval and Lobel, Orly, “The Incentives Matrix: The Comparative Effectiveness of Rewards, Liabilities, Duties and Protections for Reporting Illegality,” Texas Law Review 87 (May 2010), pp. 11511211.

13 The margin of error for the entire sample is + / –4 percent.

14 Walzer, Just and Unjust Wars, p. 136.

15 Ibid., p. 127.

16 Ibid., p. 39.

17 William Shakespeare, quoted in ibid, p. 39.

18 Dill, Janina and Shue, Henry, “Limiting the Killing in War: Military Necessity and the St. Petersburg Assumption,” Ethics & International Affairs 26, no. 3 (Fall 2012), pp. 311–33; and Christopher Kutz, “Fearful Symmetry,” in Rodin and Shue, Just and Unjust Warriors, pp. 69–86.

19 Henry Shue, “Do We Need a ‘Morality of War’?,” in Rodin and Shue, Just and Unjust Warriors, p. 99.

20 Lazar, Seth, Sparing Civilians (Oxford: Oxford University Press, 2015), p. 13.

21 Steinhoff, Uwe, “Debate: Jeff McMahan on the Moral Inequality of Combatants,” Journal of Political Philosophy 16, no. 2 (June 2008), pp. 220–26.

22 Benbaji, Yitzhak, “A Defense of the Traditional War Convention,” Ethics 118, no. 3 (April 2008); Benbaji, Yitzhak, “The Moral Power of Soldiers to Undertake the Duty of Obedience,” Ethics 122, no. 1 (October 2011), pp. 4373; and Renic, Neil C., “Justified Killing in an Age of Radically Asymmetric Warfare,” European Journal of International Relations 25, no. 2 (2019), pp. 408–30.

23 McMahan, Killing in War, p. 156.

24 Rodin, David, War and Self-Defense (Oxford: Oxford University Press, 2002), pp. 167–73.

25 Frowe, Defensive Killing, pp. 162–97; McMahan, Killing in War, pp. 213–18; and Strawser, Bradley, “Revisionist Just War Theory and the Real World: A Cautiously Optimistic Proposal,” in Allhoff, Fritz, Evans, Nicholas G., and Henschke, Adam, eds., Routledge Handbook of Ethics and War (New York: Routledge, 2013), pp. 7689.

26 See Blum, Gabriella, “The Dispensable Lives of Soldiers,” Journal of Legal Analysis 2, no. 1 (2010). Here, Blum extends this argument even further, contending that combatants who pose no threat should be immune from attack and that the principle of military necessity ought to apply to decisions to kill enemy soldiers.

27 McMahan, Jeff, “The Ethics of Killing in War,” Ethics 114, no. 4 (July 2004), p. 718.

28 McMahan, “Rethinking the ‘Just War.’”

29 McMahan, Killing in War, p. 108.

30 McMahan, “The Ethics of Killing in War,” p. 730.

31 Jeff McMahan, “The Morality of War and the Law of War,” in Rodin and Shue, Just and Unjust Warriors, p. 29.

32 See Sagan, Scott D. and Valentino, Benjamin A., “Not Just a War Theory: American Public Opinion on Ethics in Combat,” International Studies Quarterly 62, no. 3 (September 2018), pp. 548–61. Sagan and Valentino's study focuses on American public opinion on the just war principles of proportionality, discrimination, and due care.

33 Los Angeles Times, Los Angeles Times Poll #243: War against Iraq—One Month Anniversary, USLAT1991-243, version 2 (Los Angeles: Los Angeles Times, 1991), USLAT.243.R25 (question number), Roper Center for Public Opinion Research, Cornell University,

34 Los Angeles Times, Los Angeles Times/Bloomberg News Poll: George W. Bush/Congress/War in Iraq, USLAT2006-534 (New York: Bloomberg News, 2006), USLAT.092006.R47 (question number), Roper Center for Public Opinion Research, Cornell University,

35 All the results presented in this paper are weighted to match the age, gender, race, and education statistics of the American population by YouGov. See Doug Rivers, “Pew Research: YouGov Consistently Outperforms Competitors on Accuracy,” YouGov, May 13, 2016,

36 Ansolabehere, Stephen and Schaffner, Brian F., “Does Survey Mode Still Matter? Findings from a 2010 Multi-Mode Comparison,” Political Analysis 22, no. 3 (Summer 2014), pp. 285303; Yeager, David S., Krosnick, Jon A., Chang, LinChiat, Javitz, Harold S., Levendusky, Matthew S., Simpser, Alberto, and Wang, Rui, “Comparing the Accuracy of RDD Telephone Surveys and Internet Surveys Conducted with Probability and Non-Probability Samples,” Public Opinion Quarterly 75, no. 4 (Winter 2011), pp. 709747.

37 All original stories used in our survey from which quotes were taken can be found in the appendix at the end of the article.

38 The full text of all news stories, complete survey question wording, and replication data are available from the Harvard Dataverse,

39 It is possible that some subjects could have concluded that Eastland's counterattack was also unjust if they did not accept that the Westrian invasion gave Eastland a just cause for war. For example, some subjects may have felt that Eastland's counterattack was not a necessary or proportionate response to Westria's seizure of Eastland's territory and oil fields. Although this seems unlikely, a few scholars, such as Rodin (see War and Self-Defense, pp. 127–38), do contend that even an unprovoked military invasion of national territory does not always justify the use of force in self-defense (for a counterargument, see Steinhoff, Uwe, “Rodin on Self-Defense and the ‘Myth’ of National Self-Defense: A Refutation,” Philosophia 41, no. 4 [December 2013], pp. 1017–36). Empirically, our results confirm that a large majority of subjects did perceive Eastland's counterattack as just. Indeed, more than five times as many subjects agreed that Eastland was justified in its counterattack than thought Eastland was justified when it launched an unprovoked attack on Westria. To the extent that some subjects believed that Eastland's counterattack was unnecessary or disproportionate, however, our results should be considered conservative.

40 The analyst's statement that the troops would “fight hard and do whatever is asked of them” was included in the conditions of both the conscripts and volunteers to ensure that subjects would not assess Eastland's chances of winning differently across the conditions.

41 Although these conditions might appear to be double-barreled, we included a mention of conscription and the degree of Eastland's soldiers’ enthusiasm for the war in order to signal whether Eastland's soldiers have moral agency or are compelled to fight regardless of their personal feelings about the war. Thus, although the comparison between condition C and condition A cannot isolate the effect of conscription from the effect of soldiers’ beliefs in the war, it does allow us to isolate the effect of moral agency of Eastland's soldiers on the public's ethical assessments of the soldiers’ behavior.

42 Subjects who failed the manipulation check were asked to read the story again. On average, 84 percent of subjects answered the manipulation check correctly on the first attempt and all subjects answered it correctly on the second attempt.

43 Although we cannot rule out the possibility that some subjects believed that the unenthusiastic conscripts had a special responsibility not to participate in an unjust war, this kind of moral reasoning would not be consistent with revisionist theory. Future research could explore the relationship between soldiers’ enthusiasm for the war's cause and public views about soldiers’ moral culpability.

44 There were no statistically significant differences on this question between relevant conditions.

45 Since we expected subjects’ beliefs that soldiers behaved unethically to correlate with higher support for legal punishments, we coded “not ethical” using the reverse scale of the dependent variable used in figures 2, 3, and 4.

46 In the just war condition (E), 43 percent of subjects preferred no form of punishment at all, compared to 18.5 percent who preferred no punishment in the unjust war condition (D). In both conditions, more than 80 percent of subjects who supported executing the soldiers who had committed the war crimes also supported prison terms. The small number of subjects who supported execution but not prison sentences may have felt that prison was not a sufficient punishment for participating in war crimes.

47 Crawford, Neta C., “Individual and Collective Moral Responsibility for Systemic Military Atrocity,” Journal of Political Philosophy 15, no. 2 (April 2007), p. 188.

48 Approximately half of these subjects, however, also indicated that they believed that Eastland's war was unjust, roughly twice the percentage of those who did not support prison for leaders and soldiers in this condition.

49 Unsurprisingly, subjects who supported the death penalty were significantly more likely to approve of executing the soldiers who committed war crimes in condition D.

50 Liberman, Peter, “An Eye for an Eye: Public Support for War against Evildoers,” International Organization 60, no. 3 (Summer 2006), pp. 687722; and Sagan and Valentino, “Revisiting Hiroshima in Iran,” pp. 41–79.

51 For research on vicarious retribution, see Liberman, Peter and Skitka, Linda, “Vicarious Retribution in US Public Support for War against Iraq,” Security Studies 28, no. 2 (January 2019), pp. 189215; and Lickel, Brian, Miller, Norman, Stenstrom, Douglas M., Denson, Thomas F., and Schmader, Toni, “Vicarious Retribution: The Role of Collective Blame in Intergroup Aggression,” Personality and Social Psychology Review 10, no. 4 (November 2006), pp. 372–90.

52 See Greene, Joshua, Moral Tribes: Emotion, Reason, and the Gap between Us and Them (New York: Penguin, 2013); and Haidt, Jonathan, The Righteous Mind: Why Good People Are Divided by Politics and Religion (New York: Pantheon, 2012).

53 Greene, Joshua D., “Beyond Point-and-Shoot Morality: Why Cognitive (Neuro)Science Matters for Ethics,” Ethics 124, no. 4 (July 2014), pp. 695–96.

54 Herrmann, Richard K., Voss, James F., Schooler, Tonya Y. E., and Ciarrochi, Joseph, “Images in International Relations: An Experimental Test of Cognitive Schemata,” International Studies Quarterly 41, no. 3 (September 1997), pp. 403–33.

55 Merritt, Anna C., Effron, Daniel A., and Monin, Benoît, “Moral Self-Licensing: When Being Good Frees Us to Be Bad,” Social and Personality Psychology Compass 4, no. 5 (May 2010), p. 344. See also Monin, Benoît and Miller, Dale T., “Moral Credentials and the Expression of Prejudice,” Journal of Personality and Social Psychology 81, no. 1 (August 2001), pp. 3343.

56 Benbaji, Yitzhak, Falk, Amir, and Feldman, Yuval, “Commonsense Morality and the Ethics of Killing in War: An Experimental Survey of the Israeli Population,” Law & Ethics of Human Rights 9, no. 2 (November 2015).

57 Gallup, Gallup/Newsweek Poll #1971-7145: Calley Trial, USAIPOSPGONEW1971-7145, version 3 (Washington, D.C.: Gallup, 1971), USGALNEW.71CLLY.R1 (question number), Roper Center for Public Opinion Research, Cornell University,

58 Louis Harris & Associates, Harris survey (Rochester, N.Y.: Louis Harris & Associates, 1971), forthcoming survey (31107588), Roper Center for Public Opinion Research, Cornell University. Only 53 percent of respondents said he was not justified (12 percent chose “Not sure”).

59 Gary Jonathan Bass, Stay the Hand of Vengeance: The Politics of War Crimes Tribunals (Princeton, N.J.: Princeton University Press, 2000).

60 Gallup, Gallup/CNN/USA Today Poll: Congress/Bush/War in Afghanistan/Enron/Business/Slavery, USAIPOCNUS2002-03 (Washington, D.C.: Gallup, 2002), USGALLUP.02JA25.R18, USGALLUP.02JA25.R19 (question numbers), Roper Center for Public Opinion Research, Cornell University,

61 McMahan, Jeff, “On the Moral Equality of Combatants,” Journal of Political Philosophy 14, no. 4 (November 2006), pp. 392–93.

62 Lazar, “Responsibility Dilemma for Killing in War,” p. 188.

63 George C. Marshall, quoted in Luke Mogelson, “A Beast in the Heart of Every Fighting Man,” New York Times, April 27, 2011,


Just War and Unjust Soldiers: American Public Opinion on the Moral Equality of Combatants

  • Scott D. Sagan and Benjamin A. Valentino


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