Political tension, local violence and government suppression escalated in the Southern Sudan in the late 1950s and early 1960s. During this period of increasing international acceptance of “freedom fighters” and “wars of liberation”, groups of politicians in exile together with militarily trained Southerners progressively focused their efforts towards launching a rebellion; in exile, they sought international support and established political organisations. They also founded the Anya-Nya rebel movement and built military power. Their activities, combined with violent reprisals from the Government of Sudan, explain how the Southern Sudan gradually entered a state of civil war during 1963 and 1964. This process was fundamentally influenced by contingencies, unfulfilled expectations, and a lack of capacity and co-ordination, which preclude a formulaic and linear account. This article contributes to a multi-faceted and empirically grounded history of rebellion in the Southern Sudan, and challenges the common assumption that the first civil war started in 1955. The article exposes weaknesses related to a strict analytical dichotomy between “war” and “peace”. Theory–driven, comparative studies of civil war need a clearer focus on the dynamics of escalating violence and on individual and group agency.