What is the relationship between how a war ends and the post-war political order? Civil wars that end in rebel victory follow distinct war-to-peace transitions compared to the more often analyzed cases of negotiated settlement and internationally supported peacebuilding. In the cases of Uganda, Ethiopia, and Rwanda, the insurgents used the war-to-peace transition to transform their military institutions into authoritarian political parties and to consolidate power. It is not surprising that the winning military party becomes the post-war ruling party, but it is less obvious why victorious insurgents so often become powerful authoritarian parties. Using the cases of Uganda, Ethiopia, and Rwanda, this article argues that the legacies of protracted civil war and the imperatives of the war-to-peace transitions following victory provide the mechanism that links victory by insurgents to the creation of strong authoritarian parties.