I don't watch this situation closely and thought the faction fighting had abated. Instead I learnt this:
Peacekeepers from the U.N. Mission in South Sudan told their chief Hilde Johnson that people were flocking to UNMISS’ bases seeking protection. In the dark morning hours of Dec. 16, Johnson gave the order to let them in.

The result, four month later, is siege warfare. Tens of thousands of refugees struggle to survive on U.N. bases protected by lightly-armed peacekeepers—while outside the compounds’ walls, killers plan their attacks. Conditions are dire. The future is uncertain. Nearly 100,000 lives are at stake.

(Later) The U.N. has held out for four months. But as with any siege, the attackers have the advantage. It’s only a matter of time before money, supplies and political willpower run out.
Link:https://medium.com/war-is-boring/119600c57b95