Following the outbreak of civil war in South Sudan at the end of 2013, the UN Security Council passed a resolution that substantially restructured the form and function of the UN mission in South Sudan (UNMISS). This signalled a departure from its previous state-building activities to prioritise the protection of civilians. Despite the restructuring of its mandate, UNMISS finds itself between a rock and a hard place. There is no way to extricate the mission without compromising the safety of both UN personnel and civilians. This paper argues that the current mandate and operations are vulnerable to challenge by spoilers. It recommends robust UN engagement towards a peace agreement that commits the transitional government to a comprehensive process of disarmament, demobilisation and reintegration of combatants. This should also lead to a comprehensive reform of the security sector.