Intervention, war expansion, and the international sources of civil war




Langø, Hans-Inge Giske

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Why do some civil wars become interstate wars while others do not? In this dissertation I develop a theory of rebellion, rebel-sided intervention, and interstate retaliation that connects civil and interstate war. I argue that civil wars expand when rebels and third parties underestimate the government's resolve, and there are three key predictors of interstate war: the size of the local stakes relative to the third party's territory, the rebels' loss of autonomy when receiving external support, and the third party's affinity for the rebels. I evaluate the model and test its predictions using a mixed-methods approach. I use newly collected data on war expansions to show how factors such as escalation costs affect risks of intervention and retaliation, and I explore the causal mechanisms of my theory through the Afghan Civil War from 1978 to 1989. My findings have implications for models of conflict, conflict prevention, and U.S. grand strategy.



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