Although research on conflict has tended to separately study interstate conflict and civil war, states experiencing civil wars are substantially more likely to become involved in militarized disputes with other states. Scholars have typically focused on opportunistic attacks or diversionary wars to explain this domestic-international conflict nexus. The authors argue that international disputes that coincide with civil wars are more often directly tied to the issues surrounding the civil war and emphasize and unintended intervention, externalization, spillover effects from internal conflict as important sources of international friction. They empirically demonstrate that civil wars substantially increase the probability of disputes between states. An analysis of conflict narratives shows that the increased risk of interstate conflict associated with civil wars is primarily driven by states' efforts to affect the outcome of the civil war through strategies of intervention and externalization and not by an increase in conflicts over unrelated issues.