¹ This is a revised version of a paper originally prepared for the conference, Civilians at Stake: Mass Violence in Asia and Europe from 1931 to the Present, Paris, 16-18 December 2015. I am grateful to the organizers of the conference and the participants who offered valuable comments, particularly Mark Selden, Neta Crawford, and Claire Andrieu. Thanks also to Janina Dill, Benoît Pelopidas, and Henry Shue for their close readings and suggestions, and to the participants of the Law and Libations colloquium at Cornell Law School.

² or a million times more powerful than a typical blockbuster. George Lewis (email correspondence, 16 June 2016) has pointed out that the largest nuclear weapon deployed by the United States – the B53 bomb or W53 for the missile warhead, with a yield of 9 megatons – was nearly a million (0.9 million) times more powerful than the largest conventional bomb used in World War II, the British “Tallboy,” at 10,000 kg. For information on nuclear arsenals and yields, see here.

³ For discussion of these issues, see two publications of the Sciences Po, Mass Violence and Resistance – Research Network: Bas von Benda-Beckmann, “England's sole responsibility? West German historians and the Bombenkrieg,” 6 July 2016; and Johann Chapoutot, “‘The Final Solution’: The Term and the Plan,” 28 February 2016.

⁴ As a leading scholar of customary international law explains, “It is generally easier for more powerful states to engage in behavior which will significantly affect the maintenance, development, or change of customary rules than it is for less powerful states to do so.” Michael Byers, “Custom, Power, and the Power of Rules –Customary International Law from an Interdisciplinary Perspective,” Michigan Journal of International Law 17 (1995–1996), p. 115. For further discussion, see my introduction to Matthew Evangelista and Henry Shue, eds., The American Way of Bombing: Changing Ethical and Legal Norms, from Flying Fortresses to Drones (Ithaca, NY: Cornell University Press, 2014), from which some of this wording is borrowed.

⁵ “Gavotti racconta del primo bombardamento aereo,” quoting the letter of 1 November 1911, on the website of Corriere della Sera; Alan Johnston, “Libya 1911: How an Italian pilot began the air war era,” BBC News, 10 May 2011; Marco Patricelli, L'Italia sotto le bombe: Guerra aerea e vita civile 1940-1945 (Roe: Editori Laterza, 2007), pp. 3-5.

⁶ Richard. Overy, The Bombing War: Europe 1939-1945 (London: Penguin Books, 2013), p. 1681 (iBooks version).

⁷ Sahr Conway-Lanz, Collateral Damage: Americans, Noncombatant Immunity, and Atrocity after World War II (London: Routledge, 2006).

⁸ In the first years of US involvement in World War II, US bombing practices targeted militarily relevant facilities within cities, such as railroad junctures, and carried out strikes during daylight. By contrast, the British forces conducted obliteration bombing at night, when it was impossible to distinguish civilian from military targets. This US-British distinction should not be overdrawn, however, as the accuracy of the raids was such that US targeting of rail stations effectively meant aiming for the city center, and, in any case, by 1944-45, both Allies were simply trying to effect maximum destruction on cities. Henry D. Lytton, “Bombing Policy in the Rome and Pre-Normandy Invasion Aerial Campaigns of World War II: Bridge-Bombing Strategy Vindicated – and Railyard-Bombing Strategy Invalidated,” Military Affairs, vol. 47, no. 2 (April 1983), pp. 53-58. On the failure of US attempts at precision bombing during World War II, see Stephen F. McFarland, America's Pursuit of Precision Bombing, 1910-1945 (Washington, DC: Smithsonian Institution Press, 1995).

⁹ Ibid.; Pierre-Etienne Bourneuf, Bombarder l'Allemagne: L'offensive alliée sur les villes pendant la Deuxième Guerre mondiale (Paris: Presses Universitaires de France 2014); Richard Overy, The Bombing War: Europe 1939-1945 (London: Penguin Books, 2013); Raphael Littauer and Norman Uphoff, eds., The Air War in Indochina, revised edition (Boston: Beacon Press, 1972).

¹⁰ David Alan Rosenberg, “The Origins of Overkill: Nuclear Weapons and American Strategy, 1945-1960,” International Security, vol. 7, no. 4 (Spring, 1983), pp. 3-71, at pp. 14-15; Edward Kaplan, To Kill Nations: American Strategy in the Air-Atomic Age and the Rise of Mutually Assured Destruction (Ithaca, NY: Cornell University Press, 2015).

¹¹ Donald MacKenzie, Inventing Accuracy: A Historical Sociology of Nuclear Missile Guidance (Cambridge, MA: MIT Press, 1990).

¹² Carol Cohn, “Sex and Death in the Rational World of Defense Intellectuals,” Signs, vol. 12 (1987); see also Henry T. Nash, “The Bureaucratization of Homicide,” Bulletin of the Atomic Scientists (April 1980).

¹³ For the early development of “tactical” nuclear weapons in the US and USSR and the strategies for their use, see Matthew Evangelista, Innovation and the Arms Race: How the United States and the Soviet Union Develop New Military Technologies (Ithaca, NY: Cornell University Press, 1988).

¹⁴ F.J. Dyson, R. Gomer, S. Weinberg, S.C. Wright, Tactical Nuclear Weapons in Southeast Asia, Study S-266, Institute for Defense Analyses, Jason Division, March 1967. A summary and link to the document.

¹⁵ Hans M. Kristensen, “B61 LEP: Increasing NATO Nuclear Capability and Precision Low-Yield Strikes,” 15 June 2011.

¹⁶ For an analysis of these dynamics in the context of the Cold War, see Evangelista, Innovation and the Arms Race. For a recent evaluation, see Benoît Pelopidas, “A Bet Portrayed as a Certainty: Reassessing the Added Deterrent Value of Nuclear Weapons,” in George P. Shultz and James E. Goodby, eds.,The War that Must Never Be Fought (Stanford: Hoover Press, 2015), pp. 14-19.

¹⁷ Hans M. Kristensen, “General Cartwright Confirms B61-12 Bomb ”Could Be More Useable,“ 5 November 2015; and ”General Confirms Enhanced Targeting Capabilities of B61-12 Nuclear Bomb,“ 23 January 2014.

¹⁸ Pelopidas, “A Bet Portrayed as a Certainty.”

¹⁹ Henry Shue, “Force Protection, Military Advantage, and ‘Constant Care’ for Civilians: The 1991 Bombing of Iraq,” in Evangelista & Shue, eds., American Way of Bombing.

²⁰ “Gavotti racconta del primo bombardamento aereo.”

²¹ Donald Cameron Watt, “Restraints on War in the Air before 1945,” ch. 4 in Michael Howard, ed., Restraints on War: Studies in the Limitation of Armed Conflict (Oxford, UK: Oxford University Press, 1979), p. 61.

²² edn. (London: Palgrave Macmillan, 2004), p. 179. See also Yuki Tanaka, “British ‘Humane’ Bombing of Iraq during the Interwar Era,” ch. 1 in Yuki Tanaka and Marilyn B. Young, eds., Bombing Civilians: A Twentieth Century History (New York: New Press, 2009). On the use of airpower in other colonies, see V.G. Kiernan, Colonial Empires and Armies, 1815-1960 (Montreal: McGill/Queen's Press, 1998), pp. 194-201.

²³ Rodolfo Sganga, Paulo G. Tripodi, Wray R. Johnson. “Douhet's antagonist: Amedeo Mecozzi's alternative vision of air power,” Air Power History (Summer 2011).

²⁴ Reprinted as William Sherman, Air Warfare (Maxwell Air Force Base, AL: Air University Press, 2002), and discussed in Bourneuf, Bombarder l'Allemagne.

²⁵ Overy, Bombing War, pp. 1450-1451 (iBooks version).

²⁶ Robert S. Ehlers Jr., The Mediterranean Air War: Airpower and Allied Victory in World War II (Lawrence: University Press of Kansas, 2015).

²⁷ Mark Selden, “A Forgotten Holocaust: US Bombing Strategy, the Destruction of Japanese Cities and the American Way of War from World War II to Iraq,” Japan Focus, 2 May 2007; Overy, Bombing War, p. 33 (iBooks version).

²⁸ Robert Pape, Bombing to Win: Air Power and Coercion in War (Ithaca, NY: Cornell University Press, 1996).

²⁹ A notable US case of revenge bombing during World War II was the raid against Tokyo on 18 April 1942, led by Lt. Col. James Doolittle in response to the attack on Pearl Harbor the previous December.

³⁰ Charles Dunlap, “Clever or Clueless? Observations about Bombing Norm Debates,” in Evangelista & Shue, eds., American Way of Bombing, p. 116.

³¹ Interview with General Michael C. Short, Frontline, PBS, n.d.

³² Ibid.

³³ William Drozdiak, “NATO General Predicts Victory in Two Months,” Washington Post, 24 May 1999.

³⁴ Neta C. Crawford, Accountability for Killing: Moral Responsibility for Collateral Damage in America's Post-9/11 Wars (New York: Oxford University Press, 2013), esp. ch. 2.

³⁵ Richard W. Miller, “Civilian Deaths and American Power: Three Lessons from Iraq and Afghanistan,” in Evangelista & Shue, eds., American Way of Bombing; Crawford, Accountability for Killing, pp. 288-293.

³⁶ Crawford, Accountability for Killing, p. 289.

³⁷ Barack Obama, “Obama's Speech on Drone Policy,” New York Times, 23 May 2013.

³⁸ For an important, otherwise neglected aspect, see Gabrielle Hecht, Being Nuclear: Africans and the Global Uranium Trade (Cambridge, MA: MIT Press, 2012). On nuclear accidents, Scott D. Sagan, The Limits of Safety: Organizaitons, Accidents, and Nuclear Weapons (Princeton, NJ: Princeton University Press, 1993).

³⁹ Pelopidas, “A Bet Portrayed as a Certainty.” For a recent account, with video, of the consequences of one major accident, see Dave Philipps, “Decades Later, Sickness Among Airmen After a Hydrogen Bomb Accident,” New York Times, 19 June 2016.

⁴⁰ Lynn Eden, Whole World on Fire: Organizations, Knowledge, and Nuclear Weapons Devastation (Ithaca, NY: Cornell University Press, 2004).

⁴¹ Matthew Evangelista, “Nuclear Abolition or Nuclear Umbrella: Choices and Contradictions in US Proposals,” in Getting to Zero The Path to Nuclear Disarmament, Catherine McArdle Kelleher and Judith Reppy, eds. (Stanford, CA: Stanford University Press, 2011).

⁴² The wording in this paragraph and parts of the subsequent discussion draw on Matthew Evangelista, Law, Ethics, and the War on Terror (Cambridge, UK: Polity, 2008), pp. 31-34.

⁴³ Bourneuf, Bombarder l'Allemagne, pp. 161-164.

⁴⁴ House of Commons, Hansard, 21 June 1938, vol. 337, columns 919-1045, quoted in Bourneuf, Bombarder l'Allemagne, p. 165.

⁴⁵ Bourneuf, Bombarder l'Allemagne, p. 165.

⁴⁶ Quotations from Robert C. Batchelder, The Irreversible Decision, 1939-1950 (New York: Macmillan, 1961), pp. 172-173. For more detail, see Tami Davis Biddle, Rhetoric and Reality in Air Warfare: The Evolution of British and American Ideas about Strategic Bombing, 1914-1945 (Princeton, NJ: Princeton University Press, 2002).

⁴⁷ Especially Selden, “Forgotten Holocaust;” Bourneuf, Bombarder l'Allemagne; and Overy, Bombing War.

⁴⁸ Bourneuf, Bombarder l'Allemagne, pp. 183-184.

⁴⁹ Jonathan Schneer, Ministers at War: Winston Churchill and His War Cabinet (New York: Basic, 2014), pp. 100-101.

⁵⁰ Vera Brittain, “Massacre by Bombing: The Facts behind the British-American Attack on Germany,” Fellowship, vol. 10, no 3 (March 1944); on the religious leaders, Batchelder, Irreversible Decision.

⁵¹ Batchelder, Irreversible Decision, pp. 174-175.

⁵² Quoted in A. C. Grayling, Among the Dead Cities: The History and Moral Legacy of the WWII Bombing of Civilians in Germany and Japan (New York: Walker and Company, 2006), p. 187.

⁵³ Yuki Tanaka, “Firebombing and Atom Bombing: an historical perspective on indiscriminate bombing,” Japan Focus (May 2005).

⁵⁴ For an important effort to substantiate these estimates, see Milton Leitenberg, Deaths in Wars and Conflicts in the 20^th Century, Occasional Paper #29 of the Cornell University's Judith Reppy Institute for Peace and Conflict Studies, 3^rd ed., 2006, pp. 76-77.

⁵⁵ Neta Crawford, “Targeting Civilians and US Strategic Bombing Norms: Plus ça change, plus c'est la même chose?” andMiller, “Civilian Deaths and American Power,” both in Evangelista & Shue, American Way of Bombing.

⁵⁶ Crawford, “Targeting Civilians;” and Accountability for Killing, pp. 190-202.

⁵⁷ Crawford, Accountability for Killing, p. 190.

⁵⁸ For discussion of this issue, see Ward Thomas, “Victory by Duress: Civilian Infrastructure as a Target in Air Campaigns,” Security Studies, vol. 15, no. 1 (April 2006); and David Wippman and Henry Shue, “Limiting Attacks on Dual-Use Facilities Performing Indispensable Civilian Functions,” Cornell International Law Journal, vol. 35 (2002).

⁵⁹ Janina Dill, Legitimate Targets? Social Construction, International Law and US Bombing (Cambridge, UK: Cambridge University Press, 2015), p, 108.

⁶⁰ Joint Chiefs of Staff, Joint Targeting, Publication 3-60, 31 January 2013, Appendix A, point 4a, emphases added. The analysis here and even some of the wording are indebted to Henry Shue, email message, 27 December 2015.

⁶¹ See Henry Shue, “Target-selection Norms, Torture Norms, and Growing US Permissiveness,” ch. 4 in his Fighting Hurt: Rule and Exception in Torture and War (Oxford: Oxford University Press, 2016). The quotation comes from the Introduction, p. 4.

⁶² Rod Powers, “Law of Armed Conflict (LOAC) – The Rules of War,” (emphasis added). The author, identified as a “US Military Expert,” is elsewhere described as “a retired Air Force First Sergeant with 22 years of active duty service,” and author, among other works, of Veterans Benefits for Dummies, and Basic Training for Dummies.

⁶³ For a multifaceted discussion, see Claire Finkelstein, Jens David Ohlin, and Andrew Altman, eds., Targeted Killings: Law and Morality in an Asymmetrical World (Oxford: Oxford University Press, 2012).

⁶⁴ See, in particular, the articles and documents associated with the Intercept's “drone papers,” e.g., Jeremy Scahill, “The Assassination Complex,” 15 October 2015; much of this story had been uncovered by other investigative reporters, e.g., Jo Becker and Scott Shane, “Secret ‘Kill List’ Proves a Test of Obama's Principles and Will,” New York Times, 29 May 2012.

⁶⁵ Obama, “Obama's Speech on Drone Policy.”

⁶⁶ International Committee of the Red Cross, “Direct participation in hostilities: questions & answers,” 2 June 2009.

⁶⁷ John Radsan, a former lawyer in the CIA office of general counsel, quoted in Jane Mayer, “The Predator War,” The New Yorker, 26 October 2009.

⁶⁸ Mary Ellen O'Connell, “Unlawful Killing with Combat Drones: A Case Study of Pakistan, 2004-2009,” Notre Dame Law School, December 2009. On the CIA's use of private contractors from “the company formerly known as Blackwater,” see James Risen and Mark Mazzetti, “CIA Said to Use Outsiders to Put Bombs on Drones,” New York Times, 21 August 2009.

⁶⁹ James Risen, “US to Hunt Down Afghan Drug Lords Tied to Taliban,” New York Times, 10 August 2009.

⁷⁰ Office of the General Counsel, US Department of Defense, Law of War Manual, June 2015. The manual, including its treatment of human shields, has engendered a lively debate.

⁷¹ “The Pentagon's Dangerous Views on the Wartime Press,” New York Times, 10 August 2015.

⁷² Spencer Ackerman, “West Point professor calls on US military to target legal critics of war on terror,” The Guardian, 29 August 2015; Walter Olson, “Annals of bonkers scholarship: ‘Trahison des Professeurs,‘” 30 August 2015. The author of the original article is William Bradford and the fellow neoconservative is Jeremy Rabkin.

⁷³ David Kilcullen and Andrew McDonald Exum, “Death From Above, Outrage Down Below,” New York Times, 16 May 2009.

⁷⁴ Jo Becker and Scott Shane, “Secret ‘Kill List’ Proves a Test of Obama's Principles and Will,” New York Times, 29 May 2012.

⁷⁵ Ibid.

⁷⁶ Spencer Ackerman, “41 men targeted but 1,147 people killed: US drone strikes – the facts on the ground,” The Guardian, 24 November 2014.

⁷⁷ Cora Currier, “The Kill Chain,” 15 October 2015; Scahill, “Assassination Complex,”.

⁷⁸ Michael Hayden, “To Keep America Safe, Embrace Drone Warfare,” New York Times, 19 February 2016.

⁷⁹ International Committee of the Red Cross, “Direct participation in hostilities: questions & answers,” 2 June 2009.

⁸⁰ Obama, “Obama's Speech on Drone Policy.”

⁸¹ White House, Office of the Press Secretary, “Executive Order – United States Policy on Pre-and Post-Strike Measures to Address Civilian Casualties in US Operations Involving the Use of Force,” and “FACT SHEET: Executive Order on the US Policy on Pre & Post-Strike Measures to Address Civilian Casualties in the US Operations Involving the Use of Force & the DNI Release of Aggregate Data on Strike Outside Area of Active Hostilities,” 1 July 2016. In advance of release of the documents some useful discussions appeared on the Just Security website: Rita Siemion, “The Upcoming Release of Obama's Targeted Killing Policy and Casualty Numbers,” 24 June 2016, https://www.justsecurity.org/31654/upcoming-release-obamas-targeted-killing-policy-casualty-numbers/; Jameel Jaffer, “A Less-Secret Drone Campaign,” 27 June 2016.

⁸² Charlie Savage and Scott Shane, “US Reveals Death Toll From Airstrikes Outside War Zones,” New York Times, 1 July 2016. The relevant document, “Summary of Information Regarding US Counterterrorism Strikes Outside Areas of Active Hostilities,” is available here.

⁸³ Sarah Knuckey, “The Good and Bad in the US Government's Civilian Casualties Announcement,” 2 July 2016.

⁸⁴ See the discussions in Henry Shue and David Rodin, Preemption: Military Action and Moral Justification (Oxford: Oxford University Press, 2010), particularly the chapters by Marc Trachtenberg and Suzanne Unlacke.

⁸⁵ Legality of the Threat or Use of Nuclear Weapons, Advisory Opinion, International Court of Justice, Reports 1996; Timothy L.H. McCormack, “A non liquet on nuclear weapons - The ICJ avoids the application of general principles of international humanitarian law,” International Review of the Red Cross, no 316 (1997). For detailed examinations, inevitably more nuanced than my summary, see The Advisory Opinion of the International Court of Justice on the legality of nuclear weapons and international humanitarian law, a special issue of the International Review of the Red Cross, vol. 316; and Laurence Boisson de Chazournes and Philippe Sands, eds., International Law, the International Court of Justice and Nuclear Weapons (Cambridge, UK: Cambridge University Press, 1999).

⁸⁶ Michael Walzer, Just and Unjust Wars: A Moral Argument with Historical Illustrations (New York: Basic Books, 1977), ch. 6.

⁸⁷ For an excellent analysis, see Henry Shue, “Supreme Moral Emergency: Shrinking the Walzerian Exception,” ch. 12 in his Fighting Hurt: Rule and Exception in Torture and War (Oxford: Oxford University Press, 2016).

⁸⁸ For an idea of how the conferences work, see the website of the Vienna Conference on the Humanitarian Consequences of Nuclear War; for the perspective of a long-time activist, see Rebecca Johnson, “Gathering speed to ban nuclear weapons,” 8 December 2014 and “Nuclear survivors' testimony: from hell to hope,” openDemocracy website, 9 December 2014.

⁸⁹ Margarita Petrova, “Curbing the Use of Indiscriminate Weapons: NGO Advocacy in Militant Democracies,” in Matthew Evangelista, Harald Müller, and Niklas Schörnig, eds., Democracy and Security: Preferences, Norms and Policy-Making (London: Routledge, 2008); Richard Price, “Transnational Civil Society and Advocacy in World Politics,” World Politics, vol 55, no. 4 (July 2003); Sidney Tarrow, The New Transnational Activism (Cambridge, UK: Cambridge University Press, 2005).

⁹⁰ Ulrich Kühn, “70 Jahre nach Hiroshima und Nagasaki,” Heinrich Böll Stiftung, 4 August 2015; Tom Sauer & Joelien Pretorius, “Nuclear weapons and the humanitarian approach,” Global Change, Peace & Security, 2014. On the earlier campaigns, see Margarita H. Petrova, “Proportionality and Restraint on the Use of Force: The Role of Nongovernmental Organizations,” in Evangelista & Shue, American Way of Bombing; and Petrova, “Small States in Humanitarian Norm Making,” in Louis W. Pauly and Bruce W. Jentleson, eds., Power in a Complex Global System (New York: Routledge, 2014).

⁹¹ Marcus Weisgerber, “The US is Raiding its Global Bomb Stockpiles to FightISIS,” Defense One, 26 May 2016. I am grateful to Judith Reppy for calling this report to my attention.

⁹² If nuclear weapons were used against an isolated submarine or aircraft carrier, they would not produce such effects, but their use for a strictly military purpose would certainly undermine the notion of a taboo.