Do Major-Power Interventions Encourage the Onset of Civil Conflict? A Structural Analysis

What is the impact of major-power intervention on civil-war onset? A considerable hurdle to answering this question is gauging expectations about future intervention on the eve of conflict. We tackle this challenge by developing a unified theoretical and empirical model of civil-war onset and subsequent intervention. Our model allows for strategic interdependence among interveners, and our empirical strategy enables estimation of intervention expectations from equilibrium behavior. We fit the model to civil war and intervention data from the second half of the twentieth century and find that major-power intervention is primarily characterized by strategic complementarities—for example, cost sharing among allies or competition for control among rivals—rather than free-riding incentives. Through counterfactual experiments, we show that commitments to decreased intervention would raise the risk of civil war worldwide, whereas increased intervention would have little effect. Our results suggest that coordination among major powers is maximally deterring civil conflict.