Abstract
The international community has a declared intention to protect civilians from deliberate violence in civil conflicts. The optimal type of foreign intervention and its optimal timing are likely to depend on the combat strategies of the belligerents. Weak belligerents unable to provide economic incentives and security guarantees to civilians often follow a strategy of intimidation and terror. In this case, foreign financial support for one side could affect the strategies of both sides in several different ways, and the interaction between the two sides' strategies could magnify the resulting impact on civilian casualties. Using a new monthly time-series dataset, we explore the factors associated with variations in the intensity of civilian abuse by participants in the guerrilla war in Peru during the 1980s and 1990s. We show that an increase in civilian abuse by one side was strongly associated with subsequent increases in abuse by the other. In this type of war, foreign intervention could substantially reduce the impact on civilians of a sudden rise in conflict intensity, by moderating the resulting 'cycle of violence'. In practice, foreign interventions had a mixed record in Peru: financial support for the Peruvian military raised the level of violence against civilians, but counter-narcotics aid and development aid reduced it. These effects are consistent with a model in which different types of intervention have different effects on belligerents' resource capacity and on the opportunity cost of fighting.