South Sudan’s slide back into civil war continues apace. Opposition forces and militias aligned with them have taken up arms against government troops and made lightning advances in states such as Upper Nile and Jonglei, traditional hotbeds of ethnic Nuer opposition to President Salva Kiir.

The surge in violence follows Kiir’s fateful decision to dismantle the 2018 peace deal that underpinned South Sudan’s unity government, based on a power-sharing arrangement with leaders from the armed and political opposition. In March 2025, Kiir, an ethnic Dinka, had First Vice President Riek Machar, who is Nuer, placed under house arrest; six months later, the government charged Machar with treason and other serious crimes. His trial is ongoing. Machar’s movement claims credit for fomenting the new insurgency, which could lead to a conflict fought along similar ethnic lines to the 2013 civil war that erupted soon after Kiir dismissed Machar from his first stint as vice president.

Both sides now seem weaker than they were a decade ago. A series of purges and regime shake-ups over the past eighteen months, as well as an acute fiscal crisis caused by the war in neighbouring Sudan, have eroded Kiir’s power base and left him politically and militarily vulnerable. As for Machar, the government has largely cut off his communications with the outside world, depriving his opposition movement of clear leadership. A mishmash of local forces including Machar loyalists, community militias and field commanders who had previously broken from Machar now lead the military charge on the ground. The risk of factionalism and infighting is high.

Even so, the opposition has momentum. In Jonglei state, local opposition took the towns of Waat on 24 December, Yuai on 2 January and Pajut on 16 January. They are now threatening the state capital, Bor, a Dinka stronghold 200km north of the federal capital, Juba. Clashes have also broken out near oil fields in Unity state; in two remote border posts in Eastern Equatoria state; and in Central Equatoria’s Morobo County, near Juba.

Regardless of what happens next, the fighting is set to have two main consequences. First, the two sides will stoke ethnic grievances, particularly between the Dinka and the Nuer, as they seek to mobilise supporters and ready them for combat. Secondly, a flare-up in South Sudan is likely to draw in the country’s neighbours. Kiir already relies on Uganda to back his regime, with Ugandan soldiers pouring into Juba as the peace deal unravelled in March 2025. Meanwhile, the opposition’s rapid military gains have led many South Sudanese to suspect that the insurgency has a new patron: either the Sudanese Armed Forces (SAF), or one of its foreign allies. If true, Sudanese army support for the rebels could be retaliation for Juba’s close ties to the paramilitary Rapid Support Forces (RSF), which is fighting the Sudanese army for supremacy and controls much of the border between the two countries. As the conflict intensifies and spreads, there seems little doubt that South Sudan’s fragile peace has been shattered.