Since independence in Africa south of the Sahara, deadly internal conflicts have wracked the region more than any other in the world. Some of these conflicts transcended national boundaries because external states became involved in supporting rebel movements. The purpose of this paper is to contribute to an understanding of this international dimension of civil conflict. It develops a framework—unholy alignment, referring to the cooperative relationship between states and rebels—to examine how external support leads to the onset and intensification of civil conflict. I argue that external state support augments rebels’ capabilities to intensify violent demands that threaten the target government. I use data from secondary sources through historical process tracing and observation of congruence, and the case studies method, to explore three instances of Rwanda’s cooperative relations with rebels between 1994 and 1999, to show how they shaped civil wars in the DRC.