| Abstract: | Why do multiple rebel groups form in some civil wars but not others? Since 1946, only half of all civil wars were fought by a single rebel group; the rest were fought by multiple groups. This article argues that this variation is determined by the incentives political entrepreneurs have to enter a war. The higher the demand for political change and the lower the costs of fighting, the more incentives entrepreneurs have to form their own group. Analyzing UCDP data for all civil wars between 1946 and 2015 I find that the two measures of demand – the number of identifiable ethnic or religious groups in a country and the size of the disgruntled population – have the most consistent effects, but that key measures of costs such as the size of the government military also matter. A detailed analysis of the Ethiopian case further reveals the influence of external intervention on the formation of rebel groups. These results suggest that rebel groups emerge in civil wars in rational, predictable ways related to the ease by which rebel elites can mobilize separate groups for fighting. |
