Previous studies examining civil war have been limited in overlooking transnational factors. One of these factors are diaspora, groups who despite migrating from their homeland, stay oriented to it, and often involve themselves when conflict occurs. With international migrant stocks estimated at 3.6% of the world’s population they embody a potent force, representing a significant and puzzling omission in the analysis of the determinants of civil war. In this thesis, identifying three mechanisms of mobilized diaspora involvement, I argue that diaspora group involvement leads to longer duration homeland conflicts. I test these hypotheses in a quantitative study, using new data and novel diaspora mobilization variables. Using a Cox (1972) proportional hazards model I find evidence that all three mechanisms of diaspora involvement in their homeland increases the likelihood of longer duration civil wars, following the expectations of my hypotheses.