Child soldiers are often viewed as a contemporary, “new war” phenomenon, but international concern about their use first emerged in response to anti-colonial liberation struggles. Youth were important actors in anti-colonial insurgencies, but their involvement has been neglected in existing historiographies of decolonization and counterinsurgency due to the absence and marginalization of youth voices in colonial archives. This article analyses the causes of youth insurgency and colonial counterinsurgency responses to their involvement in conflict between ca. 1945 and 1960, particularly comparing Kenya and Cyprus, but also drawing on evidence from Malaya, Indochina/Vietnam, and Algeria. It employs a generational lens to explore the experiences of “youth insurgents” primarily between the ages of twelve and twenty. Youth insurgents were most common where the legitimate grievances of youth were mobilized by anti-colonial groups who could recruit children through colonial organizations as well as family and social networks. While some teenagers fought due to coercion or necessity, others were politically motivated and willing to risk their lives for independence. Youth soldiers served in multiple capacities in insurgencies, from protestors to couriers to armed fighters, in roles that were shaped by multiple logics: the need for troop fortification and sustained manpower; the tactical exploitation of youth liminality, and the symbolic mobilization of childhood and discourses of childhood innocence. Counterinsurgency responses to youthful insurgents commonly combined violence and development, highlighting tensions within late colonial governance: juveniles were beaten, detained, and flogged, but also constructed as “delinquents” rather than “terrorists” to facilitate their subsequent “rehabilitation.”