The protection of civilians is one of the items on the growing list of responsibilities assigned to peacekeepers, as these evolve into more complex, longer-term operations involving a wider range of actors. A civilian protection mandate can however take peacekeepers into direct conflict with armed elements, and calls for a new set of skills. In many cases, the requirement to protect civilians is expressed in highly qualified terms in the mandate. This research looks at the response to these challenges by UNMISS, the UN mission in South Sudan, where a third of the population (more than four million people) is displaced by violent conflict. It considers the way Protection of Civilian (PoC) sites have become a key part of the response by the UN, where more than a tenth of the internally displaced population is now given some degree of protection from attack. The challenges – such as difficult relations with the government – and failings of the mission are also discussed. The research is primarily based on field work in South Sudan, and is also informed by field work in Mali and earlier experience in Darfur.