This desk-based study assesses the contribution of humanitarian–military coordination to the protection of civilians (PoC) in South Sudan, with a particular focus on the UN Mission in South Sudan (UNMISS). The mandates of both UNMISS and its predecessor, the UN Mission in Sudan (UNMIS), have been broad and ambiguous, with highly ambitious PoC objectives. However, neither seems to have had a clear and mission-wide understanding of what was expected in terms of PoC, and the military component (particularly in UNMIS) has lacked the skills, capacity and willingness to protect civilians in any substantive way. Under-resourcing, insufficient troop numbers, weak transport and logistics capacity and competing demands and priorities have all presented operational challenges for both missions.