Abstract
While the last decades of intrastate conflicts have taught us the relevance of state sponsorship on rebel organizations, less is known about the influence of non-state actors. Case studies on the Kurdish or Tamil diaspora illustrate the importance of material and political sponsorship for rebel organizations but little is known beyond individual cases. In this paper, I examine in a global setting why diasporas support rebel groups. To understand the logic of diaspora support, I develop a new principal-agent model for diaspora support to a rebel group, with co-ethnicity as a key factor. I also review the formation and mobilization of diaspora as an external actor in civil wars. The starting point of the sequential game is the diaspora's decision to support a rebel group. The results show that kin support can be identified as a key determinant of external diaspora support of rebel groups in intrastate conflict. The paper contributes to the limited literature on diaspora support and offers further avenues for empirically testing the proposed mechanisms in the principal-agent model in a large-N framework. The findings have important implications for our understanding of the agency of non-state actors.