How do international politics influence the outbreak of civil wars? While many scholars think there is an intuitive connection between international politics and the risk of civil war, my dissertation provides the first systematic account of the shape of this relationship. Governments and opposition groups in civil conflicts often leverage international influences in their domestic conflicts, and states are often willing to supply support in pursuit of their own ends. My dissertation asks, When does an increase in the potential supply of foreign support increase the risk of a civil conflict escalating to war? More generally, how do conflicts beyond a state’s border influence the incentives of actors in domestic conflicts to compromise, repress, or escalate?

I use interstate rivalry as an entry point for theorizing how interstate conflict contributes to civil war escalation in other states. When states associate the foreign-policy orientation of other states with their own security, they are more easily drawn to adopting a proxy in civil conflicts. Rivals’ competitive relations make them wary of the spread of their adversaries’ influence, especially in nearby states, and they often intervene to bend the policies of participants and the outcome of the conflict in their favor and away from their rivals’. This potential supply of foreign support encourages increased polarization amongst civil conflict actors as they make themselves more attractive as proxies, in turn making intervention more attractive by raising the stakes of the conflict for the rivals.

I further develop this theory in a formal model of civil conflict bargaining with two interveners. A key result of this model is that more closely matched rivals are particularly destabilizing to states in their neighborhood. I test the implications of the model using novel data on the spatial distribution of rivalry and interstate conflicts. I use case studies of Lebanon in 1958 and Syria in 2011 to further test the implications of the theory. In a final chapter, I show that states engaged in rivalries develop greater repressive capacity and are more likely to deploy it against their populations.



International Politics by Other Means: External Sources of Civil War (revise and resubmit at Journal of Peace Research)

The literature on civil wars has recently turned towards their international context but lacks an account for how conflict beyond a state’s borders contributes to civil war onset. I argue that interstate rivalries can increase the risk of civil war in other states when rivals come to associate the foreign-policy orientation of other states with their own security. I present three pathways through which rivals increase the risk of civil war in other states. First, competition between rivals creates a ratchet effect by which the prospect of one’s involvement in a conflict makes it more likely that the other becomes involved. This dynamic makes support easier to secure and lowers the expected costs of war for governments and opposition groups. Second, rivals encourage domestic polarization as parties attempt to capture their influence, making domestic conflicts more intractable. Third, uncertainty over the potential for intervention by rivals increases the risk of miscalculation. I test the implications of the theory using novel spatial measures of interstate conflict and rivalry, finding robust evidence that being in the neighborhood of interstate rivals is connected with a state’s risk of civil war.

Foreign support and rebel group fragmentation

Foreign support for rebellion has largely been treated as the same as other resources in the study of rebel group behavior in civil wars. Unlike other resources used to fund rebel groups, foreign support often comes with conditions attached and rebel factions can position themselves ideologically and strategically to secure resources from actors abroad. In this project I argue that conflict beyond a states borders can contribute to the fragmentation of groups engaged in rebellion. Conflict between nearby states gives the incentive to (potential) rebels to make themselves attractive as proxies and the supply of foreign support makes it possible for new or splinter groups to form. I use data on the spatial density of interstate conflict and the emergence of new groups in civil wars to test these claims.

The International System and the Rise of Rebellion: How Constraints on Interstate War Increased the Prevalence of Civil War

The relative decline of interstate war and increase in the frequency of civil wars are two puzzles that have attracted recent scholarly interest. These phenomena are often treated independently of one another, but recent work suggests that shifts in the international system can help explain both the prevalence of interstate and civil wars. This paper proposes that, while interstate competition has produced fewer interstate wars in recent decades, it has instead contributed to a rise in the number of civil wars. As constraints on the use of force between states have increased, rivals face comparatively lower barriers to pursuing their strategic objectives by stoking conflicts or adopting proxies in third party states. I test implications of this argument using original spatial data on interstate rivalry and conflict from 1875-2007. I find that states nearby interstate rivals are significantly more likely to experience civil wars, but only in the post-1945 era, consistent with this argument. This paper helps explain the rise in civil wars relative to interstate wars, and advances the unification of the studies of interstate and within-state conflict.