Do Alliances Deter Civil Conflict? Assessing the Effect of Military Alliances on the Onset of Intrastate War.

The role of third party actors for intrastate conflict dynamics and outcomes has received considerable attention in recent years. However, our understanding of their role for the onset of civil wars is still relatively limited. We seek to contribute to this growing research field by addressing the question of how the design of military alliances affects intrastate conflict onset. We argue that the existence of formal military ties between a government and a third party state actor, in particular if they include provisions for support during intrastate conflict instances, decrease the likelihood of civil wars. Based on the Alliance and Treaty Obligation and Provisions (ATOP) and civil war onset (Correlates of War and UCDP/PRIO) data between 1816 and 2016, we find that military alliances decrease the likelihood of civil war onset. In addition, we find that alliance design plays a substantive role. Including provisions against internal threats decreases the likelihood of intrastate conflict onset even further. These findings suggest that deterrence effects of military alliances are not limited to interstate conflict but also apply to the intrastate level and further underline the importance of broadening the study of intrastate conflict to include international factors at all stages.