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ABSTRACT
What restrains states from employing chemical weapons during modern war? Despite widespread and consistent efforts by the international community to outlaw chemical weapons in the twentieth century, major deviations from this goal occur. Two of the strongest explanations that exist for this trend are the logics of deterrence and norms that consider the use of chemical weapons to be a taboo. We test these theories using factor analysis and find that norms provide a better explanation of non-use in the twentieth century among states with a chemical-weapon capability. We then conclude with avenues for future research in this burgeoning field of study, which includes closer qualitative examination of norms, as well as the expansion of the dataset to include intrastate warfare and non-state warfare.
Acknowledgments
We would like to thank Ches Thurber, the “Impact of International Law and Organization” panel at the International Studies Association—Midwest 2017 conference, and the editorial team at Nonproliferation Review for their valuable feedback on earlier drafts.
Notes
1 For a recent investigation into the interwar period, see John D. Sislin, “Chemical Warfare in the Interwar Period: Insights for the Present?” Nonproliferation Review, Vol. 25, Nos. 3–4 (2018), pp. 1–18.
2 Kim Coleman, A History of Chemical Warfare (New York: Palgrave MacMillan, 2005), p. 8.
3 Ibid., 7.
4 Eric Croddy, Clarissa Perez-Armendariz, and John Hart, Chemical and Biological Warfare: A Comprehensive Survey for the Concerned Citizen (New York: Copernicus Books, 2002), p. 171; Coleman, A History of Chemical Warfare, p. 9.
5 Croddy, Chemical and Biological Warfare, pp. 176–77.
6 Notably, the Japanese also used biological weapons against Chinese civilians. See Nuclear Threat Initiative, Nuclear Threat Initiative, <www.nti.org/learn/countries>, for country profiles and the history of biological, chemical, and nuclear programs. Also, see Stockholm International Peace Research Institute, The Problem of Chemical and Biological Warfare, Vol. 1, The Rise of CB Weapons (Stockholm: Almqvist & Wiksell, 1971), pp. 142–56, for an account addressing CW use after 1925.
7 Although the ill effects of Agent Orange on human health were evidenced years after the war, the Organisation for the Prohibition of Chemical Weapons notes that herbicides are not defined specifically in the operative paragraphs of the Chemical Weapons Convention, though they are mentioned in the preamble. See Organisation for the Prohibition of Chemical Weapons, “What Is a Chemical Weapon?” <www.opcw.org/our-work/what-chemical-weapon>. Thus, the authors find the use of Agent Orange a compelling case, but recognize that it deviates from more traditional cases of CW use.
8 This study excludes one of the more well-known recent uses of CW—in Syria—because, as a civil or intrastate war, it does not meet the parameters defined by the study.
9 For works on the normative logic, see Richard Price, The Chemical Weapons Taboo (New York: Cornell University Press, 2007); Richard Price and Nina Tannenwald, “Norms and Deterrence: The Nuclear and Chemical Weapons Taboos,” in Peter J. Katzenstein, ed., The Culture of National Security: Norms and Identity in World Politics (New York: Columbia University Press, 1996), pp. 114–52; Catherine Jefferson, “Origins of the Norm against Chemical Weapons,” International Affairs, Vol. 90, No. 3 (2014), pp. 647–61. For works addressing the deterrence logic, see John Ellis van Courtland Moon, “Chemical Weapons and Deterrence: The World War II Experience,” International Security, Vol. 8, No. 4 (1984), pp. 3–35; Scott D. Sagan, “The Commitment Trap: Why the United States Should Not Use Nuclear Threats to Deter Biological and Chemical Weapons Attacks,” International Security, Vol. 24, No. 4 (2000), pp. 85–15; William J. Perry, “Desert Storm and Deterrence,” Foreign Affairs, Vol. 70, No. 4 (1991), pp. 66–82; Avner Cohen, “Israel and Chemical/Biological Weapons: History, Deterrence, and Arms Control,” Nonproliferation Review, Vol. 8, No. 3 (2001), pp. 27–53.
10 The Convention on the Prohibition of the Development, Production, Stockpiling and Use of Chemical Weapons and on Their Destruction, January 13, 1993, 32 ILM 800 (entered into force April 29, 1997).
11 For a discussion of structural realism, see John Mearsheimer, The Tragedy of Great Power Politics (New York: Norton, 2001); Randall Schweller, “Neorealism’s Status Quo Basis: What Security Dilemma?” Security Studies, Vol. 5, No. 3 (1996), pp. 90–121; Kenneth Waltz, Theory of International Politics (Long Grove, IL: Waveland Press, 1979).
12 Patrick Morgan, Deterrence: A Conceptual Analysis, (Beverly Hills, CA: Sage 1977), pp. 77–100.
13 Christopher Achen and Duncan Snidal, “Rational Deterrence Theory and Comparative Case Studies,” World Politics, Vol. 41, No. 1 (1989), p. 151.
14 Lawrence Freedman, Deterrence (Malden, MA: Polity Press, 2004), pp. 27–29; Adam Lowther, Deterrence: Rising Powers, Rogue Regimes, and Terrorism in the Twenty-First Century (New York: Palgrave Macmillan, 2012), pp. 1–11; Glenn Snyder, “The Balance of Power and the Balance of Terror,” in Paul Seabury, ed., The Balance of Power (San Francisco: Chandler, 1965), pp. 184–201.
15 William Kaufman, “The Requirements of Deterrence,” in William Kaufman, ed., Military Policy and National Security (Princeton, NJ: Princeton University Press, 1956).
16 Susan B. Martin, “Realism and Weapons of Mass Destruction: A Consequentialist Analysis” in Sohail H. Hashmi and Steven P. Lee, eds., Ethics and Weapons of Mass Destruction: Religious and Secular Perspectives (New York: Cambridge University Press, 2004), pp. 16–42.
17 Achen and Snidal, “Rational Deterrence Theory,” pp. 143–45.
18 Richard Price and Nina Tannenwald, “Norms and Deterrence: The Nuclear and Chemical Weapons Taboos,” in Peter J. Katzenstein, ed., The Culture of National Security: Norms and Identity in World Politics (New York: Columbia University Press, 1996), pp. 116–17.
19 Ibid., pp. 114–52.
20 T.V. Paul, The Tradition of Non-use of Nuclear Weapons (Stanford, CA: Stanford University Press, 2009), pp. 17–18.
21 Stockholm International Peace Research Institute, The Problem of Chemical and Biological Warfare, Vol. 1, The Rise of CB Weapons (Stockholm: Almqvist & Wiksell, 1971), p. 334.
22 Stockholm International Peace Research Institute, The Problem of Chemical and Biological Warfare, Vol. 4, CB Disarmament Negotiations, 1920–1970 (Stockholm: Almqvist & Wiksell, 1971), p. 21; Frederic J. Brown, Chemical Warfare: A Study in Restraints (New Haven: Princeton University Press, 1968), p. 298.
23 Alexander L. George and Richard Smoke, Deterrence in American Foreign Policy: Theory and Practice (New York: Columbia University Press, 1974).
24 Richard Price, The Chemical Weapons Taboo (New York: Cornell University Press, 2007). Also see Nina Tannenwald, The Nuclear Taboo: The United States and the Non-Use of Nuclear Weapons since 1945 (Cambridge: Cambridge University Press, 2007), for discussion of how a similar logic applies to nuclear-weapon non-use.
25 Richard Price, “How Chemical Weapons Became a Taboo and Why Syria Won’t Overturn the Aversion,” Foreign Affairs, Vol. 22 (January 22, 2013), <www.foreignaffairs.com/articles/syria/2013-01-22/how-chemical-weapons-became-taboo>.
26 Price, Chemical Weapons Taboo, p. 168.
27 Richard Price, “The Shadow of Ypres: How a Whole Class of Weaponry Came to Be Seen as Indecent,” Economist, August 31, 2013, <www.economist.com/briefing/2013/08/31/the-shadow-of-ypres>.
28 Martha Finnemore, “Norms, Culture and World Politics: Insights from Sociology’s Institutionalism,” International Organizations, Vol. 50, No. 2 (1996), pp. 325–47; Martha Finnemore and Kathryn Sikkink, “International Norm Dynamics and Political Change,” in Peter Katzenstein, Robert Keohane, and Stephen Krasner, eds., Exploration and Contestation in the Study of World Politics (Cambridge, MA: MIT Press, 1999), pp. 247–77.
29 James D. Morrow and Hyeran Jo, “Compliance with the Laws of War: Dataset and Coding Rules,” Conflict Management and Peace Science, Vol. 23, No. 1 (2006), pp. 91–113; James Morrow, Order within Anarchy: The Laws of War as an International Institution (Cambridge: Cambridge University Press, 2014). Data are available at Harvard Dataverse: <https://dataverse.harvard.edu/dataset.xhtml?persistentId=hdl:1902.1/10509>.
30 Meredith Sarkees and Frank Wayman, Resort to War: 1816–2007 (Washington, DC: CQ Press, 2010). The data are available at <http://cow.dss.ucdavis.edu/data-sets/COW-war>.
31 In the Correlates of War dataset, interstate war is defined as war between members of the interstate system. Two requirements need to be met for a state to be a member of the interstate system: having a population of at least 500,000 and de facto diplomatic recognition. This means a country is being diplomatically recognized by a “legitimizer.” Before and during WWII, these legitimizers were the United Kingdom and France, and it is only after WWI that recognition extends to international organizations such as the League of Nations or United Nations, or any two major powers.
32 The Correlates of War dataset only contains the variables start_year and end_year. Thus, we cannot see at what point in time a country used CW in war. To enable us to see when, exactly, in time CW were used, we disaggregate the period of the war into yearly data. The yearly data also allow us to see the impact of time-varying covariates on the dependent variable. Directed-dyad data are the data where war between A and B can be decomposed into two observations: attack of A against B and attack of B against A. Using directed-dyad year as the unit of analysis is important because we assume that both warring countries have the same chance of using CW during war. Therefore, by relying on the directed-dyad, we can see who used CW against whom.
33 The source for this data is Morrow and Jo, “Compliance with the Laws of War.”
34 Ibid., p. 97.
35 See, for example, Gary Goertz and Paul F. Diehl, “Toward a Theory of International Norms: Some Conceptual and Measurement Issues,” Journal of Conflict Resolution, Vol. 36, No. 4 (1992), pp. 634–64; Dong-Joon Jo and Erik Gartzke, “Determinants of Nuclear Weapons Proliferation,” Journal of Conflict Resolution, Vol. 51, No. 1 (2007), pp. 167–94.
36 United Nations Office of Disarmament Affairs, “Protocol for the Prohibition of the Use in War of Asphyxiating, Poisonous or Other Gases, and of Bacteriological Methods of Warfare,” <http://disarmament.un.org/treaties/t/1925>.
37 It is important to bear in mind that both of these measures of norm strength are experimental in nature. However, certain scholars have used these measures. See Jo and Gartzke, “Determinants of Nuclear Weapons Proliferation.”
38 The national material capability here consists of three indicators: demographic, industrial, and military indicators. The demographic indicator includes total population and urban population. The industrial indicator includes iron and steel production as well as energy consumption. Finally, the military indicator includes military personnel and military expenditure. See Melvin Small and David Singer, National Material Capabilities Dataset (Ann Arbor: University of Michigan, 1990).
39 See Nuclear Threat Initiative, Nuclear Threat Initiative, <www.nti.org/learn/countries>; Arms Control Association, “Chemical and Biological Weapons Status at a Glance,” <www.armscontrol.org/factsheets/cbwprolif>; Robert Johnston, “Summary of Historical Attacks Using Chemical or Biological Weapons,” <www.johnstonsarchive.net/terrorism/chembioattacks.html>.
40 Brett Ashley Leeds, Jeffrey M. Ritter, Sara McLaughlin Mitchell, and Andrew G. Long, “Alliance Treaty Obligations and Provisions, 1815–1944,” International Interactions, Vol. 28, No. 3 (2002), pp. 237–60. The ATOP dataset defines an “alliance” as “a formal agreement among states to cooperate militarily in the face of potential or realized military conflict.”
41 Matthew Fuhrmann and Benjamin Tkach, “Almost Nuclear: Introducing the Nuclear Latency Dataset,” Conflict Management and Peace Science, Vol. 32, No. 4 (2015), pp. 443–61.
42 For an overview of democratic peace theory, see John Owen, “How Liberalism Produces Democratic Peace,” International Security, Vol. 19, No. 2 (1994), pp. 87–125.
43 Monty G. Marshall, Ted Robert Gurr, and Keith Jagger, POLITY IV Project: Political Regime Characteristics and Transition, 1800–2015 (Vienna, VA: Center for Systemic Peace, 2016).
44 D. Scott Bennett, Paul Poast, and Allan C. Stam, “NewGene: A Conceptual Manual,” June 28, 2017, SSRN, <https://ssrn.com/abstract=2596297> or <http://dx.doi.org/10.2139/ssrn.2596297>.
45 Erik Voeten, “Data and Analyses of Voting in the UN General Assembly,” in Bob Reinalda, ed., Routledge Handbook of International Organization (London: Routledge, 2013).
46 Complete/quasi-complete separation is a condition when the probability of use or non-use of CW is perfectly predicted by particular values of our predictor(s), in this case by the variable of joint democracy. In our data, we find that, when the two warring parties are democracies, they are certainly not going to use CW in war. Due to this perfect prediction problem, the maximum-likelihood (ML) estimate of the model does not exist. Under this situation, the variable that perfectly predicts the dependent variable will be dropped by Stata in order to generate ML estimates. However, dropping this variable is problematic especially when the dropped variable is correlated with other predictor(s) in our model. It will lead to specification error (which will underestimate the coefficient of the correlated predictor). To avoid this problem (i.e., the removal of the perfect predictor), we instead use penalized-maximum-likelihood estimation using Firth’s method that allows us to correct for the bias in our estimates while still retaining the perfect predictor. Penalized ML is the preferred solution because it can yield finite and consistent estimates of the parameters when the standard MLE does not exist. In Stata, we use the firthlogit command.
47 The firth-logistic-regression models for each of the component variables are shown in the Appendix.
48 Stockholm International Peace Research Institute, The Problem of Chemical and Biological Warfare, Vols. 1–6 (Stockholm: Almqvist & Wiksell, 2000).