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When and Whom to Join: The Expansion of Ongoing Violent Interstate Conflicts

Published online by Cambridge University Press:  12 February 2013

Kyle A. Joyce ,
Faten Ghosn  and
Reşat Bayer
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Abstract

The opportunity and willingness framework has received much attention in research on interstate conflict expansion. This framework is extended here by examining when and what side third parties join during ongoing conflicts. It is maintained that without examining both timing and side selection, understanding of conflict expansion is limited. The timing and side joined in interstate disputes between 1816 and 2001 are analysed using a competing risks duration model. The findings contribute novel insights into many key debates in conflict research such as balancing versus bandwagoning, as well as alliance reliability and the democratic peace. The results also indicate that relying on statistical models that do not distinguish between which side a third party can join may produce misleading results.

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Articles
Information
British Journal of Political Science , Volume 44 , Issue 1 , January 2014 , pp. 205 - 238
Copyright
Copyright © Cambridge University Press 2013 

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Footnotes

*

University of California, Davis Department of Political Science; University of Arizona School of Government and Public Policy; and Koç University Department of International Relations (email: rbayer@ku.edu.tr), respectively. Authors’ names are in reverse alphabetical order, implying equal authorship. The authors wish to thank D. Scott Bennett, Janet M. Box-Steffensmeier, Amber Boydstun, Vesna Danilovic, Errol Henderson, Jan Leighley, Doug Lemke, Glenn Palmer, Dan Reiter and the anonymous referees and the editor for their comments and suggestions. Cansu Güner, Shaina Western and Sheryl Zaks provided research assistance. Special thanks are offered in memoriam to Stuart A. Bremer. The data used in this article, along with a web appendix containing coding decisions and additional results, are available at http://psfaculty.ucdavis.edu/kjoyce/. There is an online appendix available at http://dx.doi.org/10.1017/S0007123412000506, and data replication may be requested from Bayer.

References

1 Raknerud, Arvid and Hegre, Håvard, ‘The Hazard of War: Reassessing the Evidence for the Democratic Peace’, Journal of Peace Research, 34 (1997), 385–404CrossRefGoogle Scholar

Siverson, Randolph M. and Starr, Harvey, The Diffusion of War: A Study of Opportunity and Willingness (Ann Arbor: University of Michigan Press, 1991)CrossRefGoogle Scholar

Reiter, Dan and Stam, Allan C., Democracies at War (Princeton, N.J.: Princeton University Press, 2002)CrossRefGoogle Scholar

Werner, Suzanne and Lemke, Douglas, ‘Opposites Do Not Attract: The Impact of Domestic Institutions, Power, and Prior Commitments on Alignment Choices’, International Studies Quarterly, 41 (1997), 529–546CrossRefGoogle Scholar

Melin, Molly M. and Koch, Michael T., ‘Jumping into the Fray: Alliances, Power, Institutions, and the Timing of Conflict Expansion’, International Interactions, 36 (2010), 1–27CrossRefGoogle Scholar

2 Corbetta, Renato and Dixon, William J., ‘Danger Beyond Dyads: Third-Party Participants in Militarized Interstate Disputes’, Conflict Management and Peace Science, 22 (2005), 39–61CrossRefGoogle Scholar

Regan, Patrick and Aydin, Aysegul, ‘Diplomacy and Other Forms of Intervention in Civil Wars’, Journal of Conflict Resolution, 50 (2006), 736–756CrossRefGoogle Scholar

Greig, Michael, ‘Stepping into the Fray: When Do Mediators Mediate?’, American Journal of Political Science, 49 (2005), 249–266CrossRefGoogle Scholar

3 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Siverson and Starr, The Diffusion of War; Werner and Lemke, ‘Opposites Do Not Attract’.

4 Werner, Suzanne, ‘Deterring Intervention: The Stakes of War and Third-Party Involvement’, American Journal of Political Science, 44 (2000), 720–732CrossRefGoogle Scholar

Yuen, Amy, ‘Target Concessions in the Shadow of Intervention’, Journal of Conflict Resolution, 53 (2009), 727–744CrossRefGoogle Scholar

Simmons, Beth A. and Elkins, Zachary, ‘The Globalization of Liberalization: Policy Diffusion in the International Political Economy’, American Political Science Review, 98 (2004), 171–189CrossRefGoogle Scholar

5 Siverson and Starr, The Diffusion of War; Werner and Lemke, ‘Opposites Do Not Attract’.

6 Siverson and Starr, The Diffusion of War, p. 2Google Scholar

7 Melin and Koch examine the timing of joining but focus on different theoretical arguments and use a different research design and statistical approach. Melin and Koch, ‘Jumping into the Fray’.

8 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Siverson and Starr, The Diffusion of War; Werner and Lemke, ‘Opposites Do Not Attract’; Melin and Koch, ‘Jumping into the Fray’.

9 Goodin, Robert and Tilly, Charles, eds, The Oxford Handbook of Contextual Political Analysis (Oxford: Oxford University Press, 2006)CrossRefGoogle Scholar

10 Goertz, Gary, Contexts of International Politics (New York: Cambridge University Press, 1994)CrossRefGoogle Scholar

11 Starr, Harvey, ‘ “Opportunity” and “Willingness” as Ordering Concepts in the Study of War’, International Interactions, 4 (1978), 363–387CrossRefGoogle Scholar

Most, Benjamin A. and Starr, Harvey, Inquiry, Logic and International Politics (Columbia, S.C.: University of South Carolina Press, 1989)Google Scholar

Boulding, Kenneth E., Conflict and Defense: A General Theory (New York: Harper & Row, 1962)Google Scholar

Sprout, Harold and Sprout, Margaret, The Ecological Perspective on Human Affairs (Princeton, N.J.: Princeton University Press, 1965)Google Scholar

Sprout, Harold and Sprout, Margaret, ‘Environmental Factors in the Study of International Politics’, in James N. Rosenau, ed., International Politics and Foreign Policy (New York: The Free Press, 1969), pp. 60–72Google Scholar

12 Gartzke, Erik, ‘Kant We All Just Get Along? Opportunity, Willingness, and the Origins of the Democratic Peace’, American Journal of Political Science, 42 (1998), 1–27CrossRefGoogle Scholar

Furlong, Kathryn, Gleditsch, Nils Petter and Hegre, Håvard, ‘Geographic Opportunity and Neomalthusian Willingness: Boundaries, Shared Rivers, and Conflict’, International Interactions, 32 (2006), 79–108CrossRefGoogle Scholar

13 Collier, Paul, Hoeffler, Anke and Rohner, Dominic, ‘Beyond Greed and Grievance: Feasibility and Civil War’, Oxford Economic Papers, 61 (2009), 1–27CrossRefGoogle Scholar

14 Siverson, Randolph M. and Starr, Harvey, ‘Opportunity, Willingness, and the Diffusion of War’, American Political Science Review, 84 (1990), 47–67CrossRefGoogle Scholar

15 Starr, Harvey, ‘Joining Political and Geographic Perspectives: Geopolitics and International Relations’, International Interactions, 17 (1991), 1–9CrossRefGoogle Scholar

Kadera, Kelly M., ‘Transmission, Barriers, and Constraints: A Dynamic Model of the Spread of War’, Journal of Conflict Resolution, 42 (1998), 367–387CrossRefGoogle Scholar

16 Starr, Harvey, ‘ “Opportunity” and “Willingness” as Ordering Concepts in the Study of War’, pp. 364–365Google Scholar

17 Siverson and Starr, ‘Opportunity, Willingness, and the Diffusion of War’, p. 49Google Scholar

18 Siverson and Starr, The Diffusion of War; Werner and Lemke, ‘Opposites Do Not Attract’.

19 Siverson and Starr, The Diffusion of War, p. 76Google Scholar

20 Siverson and Starr, The Diffusion of War, p. 50Google Scholar

21 Werner and Lemke, ‘Opposites Do Not Attract’.

22 Werner and Lemke, ‘Opposites Do Not Attract’, p. 545Google Scholar

23 Furlong et al., ‘Geographic Opportunity and Neomalthusian Willingness’; Most and Starr, Inquiry, Logic and International Politics.

24 Kinsella, David and Russett, Bruce, ‘Conflict Emergence and Escalation in Interactive International Dyads’, Journal of Politics, 64 (2002), 1045–1068CrossRefGoogle Scholar

25 Kinsella and Russett, ‘Conflict Emergence and Escalation in Interactive International Dyads’, p. 1050Google Scholar

26 Smith, Alastair, ‘Alliance Formation and War’, International Studies Quarterly, 39 (1995), 405–425CrossRefGoogle Scholar

Smith, Alastair, ‘To Intervene or Not to Intervene: A Biased Decision’, Journal of Conflict Resolution, 40 (1996), 16–40CrossRefGoogle Scholar

27 Gartner, Scott Sigmund and Siverson, Randolph M., ‘War Expansion and War Outcome’, Journal of Conflict Resolution, 40 (1996), 4–15CrossRefGoogle Scholar

Huth, Paul K., Extended Deterrence and the Prevention of War (New Haven, Conn.: Yale University Press, 1988)CrossRefGoogle Scholar

Bruce Bueno de Mesquita, The War Trap (New Haven, Conn.: Yale University Press, 1981)Google Scholar

Huth, Paul K., ‘Major Power Intervention in International Crises, 1918–1988’, Journal of Conflict Resolution, 42 (1998), 744–770CrossRefGoogle Scholar

28 Fearon, James, ‘Rationalist Explanations for War’, International Organization, 49 (1995), 379–414CrossRefGoogle Scholar

Meirowitz, Adam and Sartori, Anne E., ‘Strategic Uncertainty as a Cause of War’, Quarterly Journal of Political Science, 3 (2008), 327–352CrossRefGoogle Scholar

29 Melin and Koch, ‘Jumping into the Fray’.

30 Clark, David H. and Regan, Patrick M., ‘Opportunities to Fight: A Statistical Technique for Modeling Unobservable Phenomena’, Journal of Conflict Resolution, 47 (2003), 94–115CrossRefGoogle Scholar

31 Morgenthau, Hans, Politics Among Nations (New York: Knopf, 1948)Google Scholar

Waltz, Kenneth, Theory of International Politics (Reading, Mass.: Addison-Wesley, 1979)Google Scholar

32 Haldi, Stacy, Why Wars Widen: A Theory of Predation and Balancing (Portland, Ore.: Frank Cass, 2003)Google Scholar

33 Stoll, Ric, ‘The Evolution of War’, in Stuart A. Bremer and Thomas R. Cusack, eds, The Process of War: Advancing the Scientific Study of War (Amsterdam: Gordon and Breach Publishers, 1995), pp. 129–160Google Scholar

34 Morgenthau, Politics Among Nations; Waltz, Theory of International Politics.

35 Walt, Stephen, The Origins of Alliances (Ithaca, N.Y.: Cornell University Press, 1987)Google Scholar

36 Schweller, Randall L., ‘Bandwagoning for Profit: Bringing the Revisionist State Back In’, International Security, 19 (1994), 72–107CrossRefGoogle Scholar

37 Siverson and Starr, The Diffusion of War; Werner and Lemke, ‘Opposites Do Not Attract’.

38 Werner and Lemke, ‘Opposites Do Not Attract’; Schweller, ‘Bandwagoning for Profit’.

39 Reiter and Stam, Democracies at War; Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’.

40 Melin and Koch, ‘Jumping into the Fray’.

41 Altfeld, Michael F. and Bruce Bueno de Mesquita, ‘Choosing Sides in Wars’, International Studies Quarterly, 23 (1979), 87–112CrossRefGoogle Scholar

Bremer, Stuart A., ‘National Capabilities and War Proneness’, in J. David Singer, ed., The Correlates of War II: Testing Some Realpolitik Models (New York: Free Press, 1980), pp. 57–82Google Scholar

42 Gartner and Siverson, ‘War Expansion and War Outcome’.

43 Walt, The Origins of Alliances, p. 25Google Scholar

44 Regan, Patrick, Civil Wars and Foreign Powers (Ann Arbor: University of Michigan Press, 2002)Google Scholar

45 Most, Benjamin, Schrodt, Philip, Siverson, Randolph and Starr, Harvey, ‘Borders and Alliance Effects in the Diffusion of Major Power Conflict, 1816–1965’, in Charles S. Gochman and Alan Ned Sabrosky, eds, Prisoners of War?: Nation-States in the Modern Era (Lexington, Mass.: Lexington Books, 1990), pp. 209–229Google Scholar

46 Boulding, Conflict and Defense.

47 Siverson and Starr, The Diffusion of War.

48 Siverson and Starr, The Diffusion of War.

49 Werner and Lemke, ‘Opposites Do Not Attract’; Siverson and Starr, The Diffusion of War.

50 Melin and Koch, ‘Jumping into the Fray’.

51 Siverson and Starr, The Diffusion of War.

52 Werner and Lemke, ‘Opposites Do Not Attract’.

53 Peceny, Mark, Beer, Caroline C. and Sanchez-Terry, Shannon, ‘Dictatorial Peace?’, American Political Science Review, 96 (2002), 15–26CrossRefGoogle Scholar

Russett, Bruce and Oneal, John R., Triangulating Peace: Democracy, Interdependence, and International Organizations (New York: W.W. North & Company, 2001)Google Scholar

54 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Huth, ‘Major Power Intervention’; Raknerud and Hegre, ‘The Hazard of War’; Reiter and Stam, Democracies at War; Werner and Lemke, ‘Opposites Do Not Attract’.

55 Werner and Lemke, ‘Opposites Do Not Attract’.

56 Thompson, John A., ‘Conceptions of National Security and American Entry into World War II’, Diplomacy and Statecraft, 16 (2005), 671–697CrossRefGoogle Scholar

57 Raknerud and Hegre, ‘The Hazard of War’.

58 Lake, David A., ‘Powerful Pacifists: Democratic States and War’, American Political Science Review, 86 (1992), 24–37CrossRefGoogle Scholar

59 Choi, Ajin, ‘Democratic Synergy and Victory in War, 1816–1992’, International Studies Quarterly, 47 (2004), 663–682CrossRefGoogle Scholar

60 Melin and Koch, ‘Jumping into the Fray’.

61 Gartzke, Erik and Gleditsch, Kristian Skrede, ‘Why Democracies May Actually Be Less Reliable Allies’, American Journal of Political Science, 48 (2004), 775–795CrossRefGoogle Scholar

62 Mousseau, Michael, ‘Peace in Anarchy: Democratic Governance and International Conflict’ (doctoral dissertation, State University of New York at Binghamton, 1997)Google Scholar

63 Bruce Bueno de Mesquite, Morrow, James D., Siverson, Randolph M. and Smith, Alastair, ‘An Institutional Explanation of the Democratic Peace’, American Political Science Review, 93 (1999), 791–807Google Scholar

64 Werner and Lemke, ‘Opposites Do Not Attract’.

65 Raknerud and Hegre, ‘The Hazard of War’.

66 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’.

67 Kim, Chae-Han, ‘Third-Party Participation in Wars’, Journal of Conflict Resolution, 35 (1991), 659–677CrossRefGoogle Scholar

Levy, Jack S., ‘The Contagion of Great Power War Behavior, 1495–1975’, American Journal of Political Science, 26 (1982), 562–584CrossRefGoogle Scholar

Siverson, Randolph M. and King, Joel, ‘Alliances and the Expansion of War, 1815–1965’, in J. David Singer and Michael Wallace, eds, To Augur Well: Early Warning Indicators in World Politics (Beverly Hills, Calif.: Sage Publications, 1979), pp. 37–49Google Scholar

68 Sabrosky, Alan Ned, ‘Interstate Alliances: Their Reliability and the Expansion of War’, in Singer, The Correlates of War II, pp. 161–198Google Scholar

69 Altfeld and Bueno de Mesquita, ‘Choosing Sides in Wars’.

70 Leeds, Brett Ashley, ‘Alliance Reliability in Times of War: Explaining State Decisions to Violate Treaties’, International Organization, 57 (2003), 801–827CrossRefGoogle Scholar

Leeds, Brett Ashley, ‘Do Alliances Deter Aggression? The Influence of Military Alliances on the Initiation of Militarized Interstate Disputes’, American Journal of Political Science, 47 (2003), 427–439CrossRefGoogle Scholar

71 Leeds, ‘Alliance Reliability in Times of War’.

72 Gartzke and Gleditsch, ‘Why Democracies May Actually Be Less Reliable Allies’.

73 Altfeld and Bueno de Mesquita, ‘Choosing Sides in Wars’; Smith, ‘Alliance Formation and War’.

74 Bueno de Mesquita, The War Trap; Huth, Extended Deterrence; Werner, ‘Deterring Intervention’.

75 Kadera, ‘Transmission, Barriers, and Constraints’; Kim, ‘Third-Party Participation in Wars’; Raknerud and Hegre, ‘The Hazard of War’; Siverson and Starr, The Diffusion of War.

76 Leeds, Brett Ashley, Ritter, Jeffrey M., Mitchell, Sara McLaughlin and Long, Andrew G., ‘Alliance Treaty Obligations and Provisions, 1815–1944’, International Interactions, 28 (2002), 237–260CrossRefGoogle Scholar

77 Bennett, D. Scott, ‘Security, Bargaining, and the End of Interstate Rivalry’, International Studies Quarterly, 40 (1996), 157–183CrossRefGoogle Scholar

Diehl, Paul F. and Goertz, Gary, War and Peace in International Rivalry (Ann Arbor: University of Michigan Press, 2000)CrossRefGoogle Scholar

Thompson, William R., ‘Identifying Rivals and Rivalries in World Politics’, International Studies Quarterly, 45 (2001), 557–586CrossRefGoogle Scholar

78 Kim, ‘Third-Party Participation in Wars’.

79 Melin and Koch, ‘Jumping into the Fray’.

80 Findley, Michael G. and Teo, Tze Kwang, ‘Rethinking Third-Party Interventions into Civil Wars: An Actor-Centric Approach’, Journal of Politics, 68 (2006), 828–837CrossRefGoogle Scholar

81 Yamamoto, Yoshinobu and Bremer, Stuart A., ‘Wider Wars and Restless Nights: Major Power Intervention in Ongoing War’, in Singer, The Correlates of War II, pp. 199–229Google Scholar

82 Yamamoto and Bremer, ‘Wider Wars and Restless Nights’.

83 Yamamoto and Bremer, ‘Wider Wars and Restless Nights’; Kim, ‘Third-Party Participation in Wars’.

84 Ghosn, Faten, Palmer, Glenn and Bremer, Stuart A., ‘The MID3 Data Set, 1993–2001: Procedures, Coding Rules, and Description’, Conflict Management and Peace Science, 21 (2004), 133–154CrossRefGoogle Scholar

Bennett, D. Scott and Stam, Allan C., ‘EUGene: A Conceptual Manual’, International Interactions, 26 (2000), 179–204CrossRefGoogle Scholar

85 Ghosn et al., ‘The MID3 Data Set’.

86 Bennett, D. Scott and Stam, Allan C., The Behavioral Origins of War (Ann Arbor: University of Michigan Press, 2004)Google Scholar

87 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Melin and Koch, ‘Jumping into the Fray’; Mousseau, Peace in Anarchy; Reiter and Stam, Democracies at War; Werner and Lemke, ‘Opposites Do Not Attract’.

88 Siverson and Starr, The Diffusion of War; Werner and Lemke, ‘Opposites Do Not Attract’.

89 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Melin and Koch, ‘Jumping into the Fray’; Correlates of War Project State System Membership List, available at http://correlatesofwar.org (accessed 26 October 2009).

90 Reiter and Stam, Democracies at War. We focus on politically relevant triads to avoid inflating our sample by including third parties for which there is only a small probability of joining. Politically relevant triads account for about 40 per cent of all triads. In the web appendix we report the results from the full sample of potential joiners. Our findings are similar regardless of whether our sample includes all triads or only politically relevant triads.

91 If there were multiple initial belligerents (that is, more than one initiator and/or more than one target), then we created a set of initiator-target dyads. For each initiator-target dyad we included all potential joiners that met the two conditions that define a politically relevant triad.

92 We lose few joining cases by limiting the set of all potential joiners to those that are politically relevant. We lose fifty-four cases of joining: twenty-four on the initiator and thirty on the target. This suggests that contiguous states and/or major powers account for most of the joining.

93 In addition, when using the year as the temporal unit, care has to be taken to ensure that independent variables, such as alliances, are actually operative during the MID. For example, when the temporal unit is the year, it is necessary to ensure that an alliance between a third party and an initial belligerent was in effect during the MID and did not end before the MID began or start after the MID ended.

94 Box-Steffensmeier, Janet M. and Jones, Bradford S., Event History Modeling (Cambridge: Cambridge University Press, 2004)CrossRefGoogle Scholar

95 We prefer the Cox model to its parametric alternatives because it makes no assumption about the distributional form of the baseline hazard rate (that is, the risk of third-party joining as a MID persists).

96 Gordon, Sanford C., ‘Stochastic Dependence in Competing Risks’, American Journal of Political Science, 46 (2002), 200–217CrossRefGoogle Scholar

Fukumoto, Kentaro, ‘Systematically Dependent Competing Risks and Strategic Retirement’, American Journal of Political Science, 53 (2009), 740–754CrossRefGoogle Scholar

Han, Aaron and Hausman, Jerry A., ‘Flexible Parametric Estimation of Duration and Competing Risk Models’, Journal of Applied Econometrics, 5 (1990), 1–28CrossRefGoogle Scholar

Hill, Daniel H., Axinn, William G. and Thorton, Arland, ‘Competing Hazards with Shared Unmeasured Risk Factors’, Sociological Methodology, 23 (1993), 245–277CrossRefGoogle ScholarPubMed

97 Event history models can incorporate these censored observations because a third party is at risk of joining at each time point during a MID, and third parties that do not join contribute information to the baseline hazard through the survivor function.

98 Box-Steffensmeier, Janet M. and Zorn, Christopher J.W., ‘Duration Models and Proportional Hazards in Political Science’, American Journal of Political Science, 45 (2001), 972–988CrossRefGoogle Scholar

99 Singer, J. David, Bremer, Stuart and Stucky, John, ‘Capability Distribution, Uncertainty, and Major Power War, 1820–1965’, in Bruce M. Russett, ed., Peace, War, and Numbers (Beverly Hills, C.A.: Sage Publications, 1972), pp. 19–48Google Scholar

100 Gleditsch, Kristian S. and Ward, Michael D., ‘Measuring Space: A Minimum Distance Database and Applications to International Studies’, Journal of Peace Research, 38 (2001), 739–758CrossRefGoogle Scholar

Weidmann, Nils B., Kuse, Doreen and Gleditsch, Kristian Skrede, ‘The Geography of the International System: The CShapes Dataset’, International Interactions, 36 (2010), 86–106CrossRefGoogle Scholar

101 Bueno de Mesquita, The War Trap, p. 108Google Scholar

102 Bueno de Mesquita, The War Trap, p. 104Google Scholar

103 Bueno de Mesquita, The War Trap.

104 Bueno de Mesquita, The War Trap, p. 105Google Scholar

105 We account for the fact that some MIDs have multiple initial belligerents by summing the CINC scores of the initial belligerents on each side.

106 In all of these operationalizations, if a MID lasts past December 31 of a given year, then a state's CINC score can change, which means that a potential joiner's capability contribution to an initial belligerent can change as well.

107 Stinnett, Douglas, Tir, Jaroslav, Schafer, Philip, Diehl, Paul F. and Gochman, Charles, ‘The Correlates of War Project Contiguity Data, Version 3’, Conflict Management and Peace Science, 19 (2002), 58–66CrossRefGoogle Scholar

108 Marshall, Monty G. and Jaggers, Keith, Polity IV Project: Political Regime Characteristics and Transitions, 1800–2002. Dataset Users’ Manual (College Park, Md.: Center for International Development and Conflict Management, 2002)Google Scholar

109 Leeds et al., ‘Alliance Treaty Obligations and Provisions’.

110 William R. Thompson, ‘Identifying Rivals and Rivalries in World Politics’.

111 Correlates of War Project State System Membership List.

112 We also estimated these models on three additional samples: (1) all triads, (2) all triads without World Wars I and II and 3) politically relevant triads without World Wars I and II. We note the differences in the results for our risk specific models in the politically relevant triads sample and the three other samples.

113 Licht, Amanda A., ‘Change Comes with Time: Substantive Interpretation of Nonproportional Hazards in Event History Analysis’, Political Analysis, 19 (2011), 227–243CrossRefGoogle Scholar

114 Formally, the percentage change in the hazard ratio is: $$$ \ % \rDelta {{{\rm{h}}}_{\rm{i}}}{\rm{(t)}} = ({{e}^{({{{\rm{X}}}_{\rm{i}}}{\rm{ - }}{{{\rm{X}}}_{\rm{j}}}{\rm{)(}}{{\beta }_{\rm{1}}} + {{\beta }_{\rm{2}}}{\rm{ln(t))}}}} {\rm{ - }}1)\times 100 $$$. See Licht (2011). The summary statistics reveal that the capability variable is skewed, with most values clustering near zero. As a result, a percentage change in the hazard ratio that is calculated, for example, using the mean value and one standard deviation above the mean value, is not meaningful because the percentage of third parties that have that value of capability is quite small. For example, in the Join Either Initiator or Target model, one standard deviation above the mean is 0.28, and only 12 per cent of potential joiners have a value above that number. Additionally, one standard deviation below the mean is −0.1, which is nonsensical since a third party's capability contribution is always greater than zero. Thus in order to calculate the substantive effect of capability on the risk of joining we used the first, second and third quartiles. In the Join Either Initiator or Target model, the value that cuts off the first quartile is 0.001, the value that cuts off the second (or median) quartile is 0.007 and the value that cuts off the third quartile is 0.05. Therefore we calculate the percentage change in the hazard ratio if a third party's capability increases from the first to the second quartile (an increase of 0.006) and from the second to the third quartile (an increase of 0.043). In the Join Initiator model, the value that cuts off the first quartile is 0.0001, the value that cuts off the second quartile is 0.0015 and the value that cuts off the third quartile is 0.016. An increase in a third party's capability from the first to the second quartile is 0.0014 and from the second to the third quartile is 0.015. In the Join Target model, the value that cuts off the first quartile is 0.0002, the value that cuts off the second quartile is 0.003 and the value that cuts off the third quartile is 0.03. An increase in a third party's capability from the first to the second quartile is 0.003 and from the second to the third quartile is 0.027.

115 In the Join Initiator model, the initial effect of capability is positive in all four samples but is only statistically significant in the politically relevant triads sample with World Wars I and II. The effect of capability does not significantly decrease over time in any of the samples except the all triads sample without the world wars, in which the effect increases over time but not significantly. In the Join Target model, the effect of capability is initially positive and statistically significant, and significantly decreases over time in all four samples.

116 Altfeld and Bueno de Mesquita, ‘Choosing Sides in Wars’; Bremer, ‘National Capabilities and War Proneness’; Huth, Extended Deterrence.

117 Walt, The Origins of Alliances, p. 25Google Scholar

118 Waltz, Theory of International Politics; Melin and Koch, ‘Jumping into the Fray’.

119 In both the Join Initiator and Join Target models, the initial effect of geographic proximity is positive and statistically significant, and significantly decreases over time in all four samples except the politically relevant triads samples without the world wars. In the politically relevant triads sample without the world wars, the effect of geographic proximity is positive and statistically significant but does not change over time in either the Join Initiator or the Join Target model.

120 The formula for the percentage change in the hazard ratio is the same as for continuous variables (see fn. 114), where Xi = 1 and Xj = 0.

121 Siverson and Starr, The Diffusion of War; see also Melin and Koch, ‘Jumping into the Fray’.

122 Licht, ‘Change Comes with Time’, p. 232Google Scholar

123 Raknerud and Hegre, ‘The Hazard of War’; Werner and Lemke, ‘Opposites Do Not Attract’.

124 Mousseau, Peace in Anarchy; Reiter and Stam, Democracies at War; Lake, ‘Powerful Pacifists’; Choi, ‘Democratic Synergy’.

125 In the Join Initiator model, the initial effect of autocracy is positive and statistically significant, and significantly decreases over time in all four samples. In the Join Target model, the initial effect of autocracy is negative and not statistically significant in both samples with the world wars, but positive in both samples without the world wars. However, the effect of autocracy is not statistically significant in any of the samples. The initial effect of autocracy increases over time but is not significant in any of the samples except the politically relevant triads sample without the world wars, in which the effect is negative but not significant.

126 Raknerud and Hegre, ‘The Hazard of War’; Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Werner and Lemke, ‘Opposites Do Not Attract’.

127 Leeds et al., ‘Alliance Treaty Obligations and Provisions’, p. 240.

128 Siverson and Starr, The Diffusion of War; Melin and Koch, ‘Jumping into the Fray’.

129 Leeds et al., ‘Alliance Treaty Obligations and Provisions’.

130 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Leeds, ‘Alliance Reliability in Times of War’; Leeds, ‘Do Alliances Deter Aggression?’; Smith, ‘To Intervene or Not to Intervene’.

131 Siverson and Starr, The Diffusion of War.

132 Diehl and Goertz, War and Peace in International Rivalry.

133 Haldi, Why Wars Widen. In the Join Initiator model, the initial effect of rivalry is positive and statistically significant in all four samples. However, the effect of rivalry significantly decreases over time in all of the samples except the politically relevant triads sample that includes World Wars I and II. Since rivalry did not violate the proportional hazards assumption in that sample, we did not include an interaction with the natural log of time. In the Join Target model, the effect of rivalry is positive and statistically significant in both politically relevant triads samples, but is positive and not statistically significant in both ‘all triads’ samples. In addition, the effect of rivalry changes inconsistently over time across the four samples; it is positive in the all triads sample, positive and significant in the all triads sample without the world wars, was not included in the politically relevant triads sample without the world wars (because it did not violate the proportional hazards assumption), and is negative and not significant in the politically relevant triads sample without the world wars.

134 In the Join Initiator model, the initial effect of previous major power joining is positive but not statistically significant in any of the samples except the politically relevant triads sample without World Wars I and II, in which the effect is negative but not statistically significant. The effect of previous major power joining increases over time in all of the samples, but is not statistically significant. In the Join Target model, the initial effect of previous major power joining is positive and statistically significant and significantly decreases over time in all four samples.

135 Yamamoto and Bremer, ‘Wider Wars and Restless Nights’.

136 Corbetta, ‘Determinants of Third Parties’ Intervention and Alignment Choices’; Corbetta and Dixon, ‘Danger Beyond Dyads’.

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