This article draws together historical sources and political science insights to test the emergence of civil war at the end of empire. It focuses on civil conflict in two French colonial territories, Vietnam and Algeria, during and immediately after 1945. It investigates the civil war dynamics of local, often intra-ethnic contests among anticolonial oppositionists. Concentrating on the early, formative years of insurgent violence, we aim to demonstrate that elements of civil war pre-existed the supposed outbreak of decolonisation conflicts – 1946 in Vietnam and 1954 in Algeria. Our approach combines narrative assessments of the early phases of these conflicts with analysis of their civil war dynamics. As we seek to demonstrate, cycles of internecine killing, massacre and counter-massacre, normalized summary killing, maltreatment of detainees, and loss of distinction between civilians, seditionists, and ‘traitors’. Our argument is that decolonisation violence in both Vietnam and Algeria may be usefully rethought in civil war terms.