Jérôme Tubiana, Claudio Gramizzi and I have a 256 page working paper with Small Arms Survey's HSBA project, that looks at the history of the South Sudanese Civil War in Unity State, 2013-16.
It includes analysis of the UN's decision to arm the rebels at the outset of the conflict, the manipulation of humanitarian aid, and a blow by blow account of the war, county by county.
You can read it here.