Altering Capabilities or Imposing Costs? Intervention Strategy and Civil War Outcomes

How do military interventions affect the outcome of civil wars? The diversity of military interventions makes it difficult to answer this question; their variation means that they do not affect civil wars in a straightforward way. In particular, strategy and timing play a pivotal role in determining the effect of an intervention. Thus, I isolate three intervention strategies: indirect (bolstering the capabilities of the supported side), direct-conventional (degrading the capabilities of the opposition), and direct-unconventional (imposing costs on the opposition). I evaluate the impact of these strategies on the outcome of civil wars using a dataset of all civil wars from 1944 to 2007. My analysis reveals that the efficacy of intervention strategies varies over time. Third-party support for rebel organizations is most effective during a critical window early in a civil war. In contrast, direct military assistance for the government increases the odds of a government victory only once a civil war becomes protracted. It also reduces the odds of a negotiated outcome to the conflict, whereas indirect support for the government proves most effective early in the war. This work demonstrates that pooling all interventions together risks overlooking important differences in their effects on civil wars. It also carries with it important implications for states considering interventions in civil wars.