¹ McGirk, Tim, ‘The Monster Within’, Time Magazine, 26 (26 January 2004), 32–55Google Scholar.

² Byman, Daniel, Chalk, Peter, Hoffman, Bruce, Rosenau, William and Brannan, David, Trends in Outside Support for Insurgent Movements (Santa Monica, Calif.: RAND Corporation, 2001)CrossRefGoogle Scholar; Carter, David, ‘The Compellence Dilemma: Non-Domestic Disputes with Radical Groups’ (working paper, Pennsylvania State University, 2010)Google Scholar; Davis, David and Moore, Will, ‘Ethnicity Matters: Transnational Ethnic Alliances and Foreign Policy Behaviour’, International Studies Quarterly, 41 (1997), 171–181CrossRefGoogle Scholar; Enders, Walter and Sandler, Todd, The Political Economy of Terrorism (Cambridge: Cambridge University Press, 2005)CrossRefGoogle Scholar; Gleditsch, Kristian, Salehyan, Idean and Schultz, Kenneth, ‘Fighting at Home, Fighting Abroad: How Civil Wars Lead to International Disputes’, Journal of Conflict Resolution, 52 (2008), 479–506CrossRefGoogle Scholar; Salehyan, Idean, Rebels Without Borders (Ithaca, N.Y.: Cornell University Press, 2009)CrossRefGoogle Scholar; Schultz, Kenneth, ‘War as an Enforcement Problem: Interstate Conflict over Rebel Support in Civil Wars’, International Organization 64 (2010), 281–312CrossRefGoogle Scholar.

³ Brophy-Baermann, Bryan and Conybeare, John, ‘Retaliating Against Terrorism: Rational Expectations and the Optimality of Rules versus Discretion’, American Journal of Political Science, 38 (1994), 196–210CrossRefGoogle Scholar; Byman, Daniel, Deadly Connections: States that Sponsor Terrorism (Cambridge: Cambridge University Press, 2005)CrossRefGoogle Scholar; William Zartman, I., Elusive Peace: Negotiating an End to Civil Wars 1995–1996 (Washington, D.C.: The Brookings Institution, 1995), pp. 3–31Google Scholar.

⁴ Schelling, Thomas, The Strategy of Conflict (Oxford: Oxford University Press, 1960)Google Scholar.

⁵ In the aforementioned case of Pakistan, the model would argue that Musharraf gained bargaining power in his negotiations with India due to the very substantial risk that the Kashmiri militants would reject bargaining and punish him for making peace.

⁶ Byman, Daniel, Chalk, Peter, Hoffman, Bruce, Rosenau, William and Brannan, David, Trends in Outside Support for Insurgent Movements (Santa Monica, Calif.: RAND Corporation, 1999)Google Scholar; Byman, Deadly Connections.

⁷ Hoffman, Bruce, Inside Terrorism (New York: Columbia University Press, 1998)Google Scholar; Palmer, Glenn and Clifton Morgan, T., A Theory of Foreign Policy (Princeton, N.J.: Princeton University Press, 2006)Google Scholar; Salehyan, Idean, Rebels Without Borders (Ithaca, N.Y.: Cornell University Press, 2009)CrossRefGoogle Scholar.

⁸ While it is true that some sponsors create militants, I focus only on the cases where militant groups have already formed and are engaging in conflict against the government, and leave the other case to future research.

⁹ Byman, Deadly Connections; Salehyan, Rebels Without Borders; Zartman, Elusive Peace.

¹⁰ Conybeare, John, ‘A Portfolio Diversification Model of Alliances: The Triple Alliance and the Triple Entente 1879–1914’, Journal of Conflict Resolution, 36 (1992), 53–85CrossRefGoogle Scholar; Lake, David, Entangling Relations: American Foreign Policy in its Century (Princeton, N.J.: Princeton University Press, 1999)Google Scholar; Palmer and Morgan, Theory of Foreign Policy.

¹¹ Byman, Deadly Connections; Lake, David, ‘Rational Extremism: Understanding Terrorism in the Twenty-First Century’, International Organization, 56 (2002), 15–29Google Scholar.

¹² Kuperman, Alan J., ‘The Moral Hazard of Humanitarian Intervention: Lessons from the Balkans’, International Studies Quarterly, 52 (2008), 49–80CrossRefGoogle Scholar; Lake, Entangling Relations; Miller, Gary J.. ‘The Political Evolution of Principal–Agent Models’, Annual Review of Political Science, 8 (2005), 203–225CrossRefGoogle Scholar.

¹³ Brophy-Baermann and Conybeare, ‘Retaliating Against Terrorism’; Byman, Deadly Connections; Carter, ‘Compellence Dilemma’; Gleditsch et al., ‘Fighting at Home’; Lake, David and Rothchild, Donald eds, The International Spread of Ethnic Conflict (Princeton, N.J.: Princeton University Press, 1998): pp. 3–33Google Scholar; Salehyan, Rebels Without Borders.

¹⁴ Schultz, ‘Enforcement Problem’.

¹⁵ Byman, , Deadly Connections, pp. 155–86Google Scholar.

¹⁶ Fearon, James, ‘Domestic Political Audiences and the Escalation of International Disputes’, American Political Science Review, 88 (1994), 379–415CrossRefGoogle Scholar; Schultz, Kenneth, ‘Domestic Opposition and Signaling in International Crises’, American Political Science Review, 92 (1998), 829–844CrossRefGoogle Scholar.

¹⁷ Fearon, James, ‘Signaling Foreign Policy Interests: Tying Hands Versus Sinking Costs’, Journal of Conflict Resolution, 41 (1997), 68–90CrossRefGoogle Scholar; Slantchev, Branislav, ‘Military Coercion in Interstate Crises’, American Political Science Review, 99 (2005), 533–547CrossRefGoogle Scholar.

¹⁸ Putnam, Robert. ‘Diplomacy and Domestic Politics: The Logic of Two-Level Games’, International Organization, 42 (1988), 427–460CrossRefGoogle Scholar; Schelling, Strategy of Conflict; Tarar, Ahmer, ‘Constituencies and Preferences in International Bargaining’, Journal of Conflict Resolution, 49 (2005), 383–407CrossRefGoogle Scholar.

¹⁹ Atran, Scott, ‘The Genesis of Suicide Terrorism’, Science, 299 (2003), 1534–1539CrossRefGoogle Scholar; Lake, ‘Rational Extremism’, pp. 15–29.

²⁰ Bar-Joseph, Uri. ‘The Conceptualization or Deterrence in Israeli Strategic Thinking’, Security Studies, 7 (1998), 145–181CrossRefGoogle Scholar; Chellaney, Brahma, ‘Fighting Terrorism in Southern Asia’, International Security, 26 (2001), 94–116CrossRefGoogle Scholar.

²¹ Enders, Walter and Sandler, Todd. ‘The Effectiveness of Anti-Terrorism Policies: Vector-Autoregression Intervention Analysis’, American Political Science Review, 87 (1993), 829–844CrossRefGoogle Scholar.

²² Morrow, James, Game Theory for Political Scientists (Princeton, N.J.: Princeton University Press, 1994), pp. 23–32Google Scholar.

²³ In the course of the discussion, I refer to G as ‘she’, S as ‘he’ and M as ‘it’.

²⁴ The assumption that S gains no intrinsic value for keeping M operational is included such that M's preferences for survival may diverge from S's preferences for policy concessions. The model allows for the possibility that M and S share very similar preferences. However, if we consider a situation in which both S and M ₁ had the same preferences, S would be equally well off if M ₁ did not survive and a separate group M ₂ accomplished its policy objective, whereas M ₁ would prefer to survive and accomplish the policy objective. It is therefore reasonable to assume that S gains no intrinsic value for sustaining any one M, but only gains value if the M that is operational accomplishes his policy objective.

²⁵ A case example of this is the behaviour of the Kashmiris towards Musharraf following his agreement with India to curb militant violence after the 2001 attack on the Indian Parliament building.

²⁶ While it may be possible that G is not completely credible, and that G may renege on its commitment to S once M is disarmed, this possibility is left out of the current model set-up. The reason this is the case is because if G were to renege, S could reconstitute the group and begin violence again. This threat to retaliate should ensure that G would fulfil the terms, and deter G from defecting. Again, while it is possible to include this, I do not do so in the presentation for space considerations and in order to simplify the model. The results do not substantively change with this feature included.

²⁷ Enders and Sandler, Political Economy; Walter, Barbara, ‘Building Reputation: Why Governments Fight Some Separatists but Not Others’, American Journal of Political Science, 50 (2006), 313–330CrossRefGoogle Scholar.

²⁸ The completed version of the proofs is in the Appendix.

²⁹ Since θ* is defined as a probability, it must be true that 0 ≤ θ* ≤ 1. Therefore, assume that if (1−γ−κ_M)/x < 0, θ* = 0 and if (1−γ−κ_M)/x > 1, θ* = 1.

³⁰ Since we solve for x using the quadratic equation, there are two possible solutions. The solution for which x < 0 is again eliminated by assumption. Also, if 1−γ−κ_M < 0, assume that x* = 0.

³¹ Since we solve for x using the quadratic equation, there are two possible solutions. The solution for which x < 0 is again eliminated by assumption. Also, if 1−γ−κ_M < 0, assume that x* = 0.

³² Indicated by a value of κ_M→0.

³³ Proof of this is in the Appendix.

³⁴ As with the previous beliefs, 0 ≤ C*_G ≤ 1, so that if C*_G < 0, C*_G = 0, and if C*_G > 1, C*_G = 1.

³⁵ For a further description, please see Duiker, William J., Sacred War: Nationalism and Revolution in a Divided Vietnam (Boston, Mass.: McGraw Hill, 1995)Google Scholar.

³⁶ Please see Coll, Steve, Ghost Wars: The Secret History of the CIA, Afghanistan, and Bin Laden, from the Soviet Invasion to September 10, 2001 (New York: Penguin, 2004)Google Scholar.

³⁷ Byman, Deadly Connections; Salehyan, Rebels without Borders.

³⁸ Byman et al., Trends in Outside Support; O'Brien, Sean, ‘Foreign Policy Crises and the Resort to Terrorism: A Time-Series Analysis of Conflict Linkages’, Journal of Conflict Resolution, 40 (1996), 320–335CrossRefGoogle Scholar.

³⁹ Harbom, Lotta, Erik Melander and Peter Wallenstein, ‘Dyadic Dimensions of Armed Conflict, 1946–2007’, Journal of Peace Research, 45 (2008), 697–710CrossRefGoogle Scholar.

⁴⁰ Byman, Deadly Connections; Gleditsch et al., ‘Fighting at Home’; Salehyan, Rebels without Borders.

⁴¹ Thompson, William R., ‘Identifying Rivals and Rivalries in World Politics’, International Studies Quarterly, 45 (2001), 557–586CrossRefGoogle Scholar.

⁴² In terms of the model, using the Thompson rivals avoids cases where 1−δρ−c_S > 0 is likely to be fulfilled.

⁴³ Byman, , Deadly Connections, pp. 10–12Google Scholar.

⁴⁴ Byman, , Deadly Connections, pp. 10–12Google Scholar.

⁴⁵ Considering both active and passive support as the same behaviour is particularly problematic for testing the hypothesis here, largely because the predicted effect is somewhat similar to that of the ‘weak state’ hypothesis. The ‘weak state’ hypothesis predicts that the likelihood in which a state becomes a sanctuary for insurgencies increases as its weakness increases. Here, the hypothesis predicts that the likelihood in which a state becomes an active supporter increases if the state is moderately weak.

⁴⁶ We do identify sponsorship from Mozambique during the 1980s. These will be further discussed as part of an out of sample test after the empirical analysis.

⁴⁷ It is certainly the case that in previous periods, and the period following 1989–2001, sponsorship does occur in Latin America. However, in this snapshot, there were no cases that could be conclusively classified as sponsorship, based on the definition.

⁴⁸ Benson, Michelle and Kugler, Jacek, ‘Power Parity, Democracy, and the Severity of Internal Violence’, Journal of Conflict Resolution, 42 (1998), 196–209CrossRefGoogle Scholar; Fearon, James and Laitin, David, ‘Ethnicity, Insurgency, and Civil War’, American Political Science Review, 97 (2003), 75–90CrossRefGoogle Scholar.

⁴⁹ Arbetman, Marina and Kugler, Jacek, Political Capacity and Economic Behaviour (Boulder, Colo.: Westview, 1997)Google Scholar.

⁵⁰ O'Brien, , ‘Foreign Policy Linkages and the Resort to Terrorism’, pp. 320–35Google Scholar; Salehyan, Rebels without Borders.

⁵¹ Fearon, and Laitin, , ‘Ethnicity, Insurgency, and Civil War’, pp. 75–90Google Scholar; Hegre, Håvard and Sambanis, Nicholas, ‘Sensitivity Analysis of Empirical Results on Civil War Onset’, Journal of Conflict Resolution, 50 (2004); 508–525CrossRefGoogle Scholar. The data for the control variables were generated using Scott Bennett, D. and Stam, Allan, ‘EUgene: A Conceptual Manual’, International Interactions, 26 (2000), 179–204CrossRefGoogle Scholar.

⁵² David Singer, J., ‘Reconstructing the Correlates of War Dataset on Material Capabilities of States, 1816–1985’, International Interactions, 14 (1987), 115–132CrossRefGoogle Scholar.

⁵³ Fearon and Laitin, ‘Ethnicity, Insurgency, and Civil War’.

⁵⁴ Fearon and Laitin, ‘Ethnicity, Insurgency, and Civil War’; Hegre and Sambanis, ‘Sensitivity Analysis of Empirical Results on Civil War Onset’.

⁵⁵ Jackman, Robert. Power without Force (Ann Arbor: University of Michigan Press, 1993), pp. 73–155Google Scholar.

⁵⁶ I do not include measures for the government's Elevation Difference and Ethnic Fractionalization due to multicollinearity. Although the results hold when the sponsor's Elevation Difference and Ethnic Fractionalization scores are dropped, the model presented produces a better fit and allows us to examine the explanatory variable of interest when controlling for these factors.

⁵⁷ To illustrate with an example, if Syria chose to sponsor Hamas against Israel from 1989 to 2000, this test would only include one observation for Syria in 1989, and would drop Israel/Syria dyads between 1990 and 2000.

⁵⁸ Carter, David and Signorino, Curtis, ‘Back to the Future: Modeling Time Dependence in Binary Data’, Political Analysis, 18 (2010), 271–292CrossRefGoogle Scholar.

⁵⁹ This does not suggest that the ‘weak state hypothesis’ in the literature is incorrect. Since the sponsorship variable only codes those cases of intentional assistance, it is entirely possible that autonomous militants adopt transnational campaigns of violence from weak or failing states. This is not ruled out by the analysis here. The analysis does suggest, however, that when examining cases of deliberate sponsorship, moderately weak states are more likely to engage in this behaviour than very weak states.

⁶⁰ Arnold, Guy, Wars in the Third World Since 1945 (London: Cassell, 1991)Google Scholar.

⁶¹ It is interesting to note that several of these states have relatively higher RPC scores, and the mean supporter RPC score in the group is 1.45. However, the standard deviation is 0.92, which indicates substantial variation.

⁶² Thomas, Scott, The Diplomacy of Liberation: The Foreign Relations of the African National Congress since 1960 (London: Tauris Academic Studies, 1996), pp. 2–173Google Scholar.

⁶³ Byman, Deadly Connections; O'Brien, ‘Foreign Policy Crises and the Resort to Terrorism’; Salehyan, Rebels without Borders.