The Sudanese Armed Forces (SAF) captured more than 10 South Sudanese citizens as part of the fight to retake the North Kordofan community of Kazigil in late December 2025.
The South Sudanese were fighting on the side of the paramilitary Rapid Support Forces (RSF), which has taken parts of the Kordofan region on the border with South Sudan in recent months.
The involvement of South Sudanese fighters on the side of the RSF prompted the Sudanese government to contact its counterparts in South Sudan regarding its citizens. The SAF has claimed since late 2024 that armed groups from South Sudan are fighting on the side of the RSF.
The involvement of South Sudanese citizens on the battlefield reveals the complex relationship between the two countries, one that appears to be dragging South Sudan into the conflict even as it could be on the brink of its own civil war.
“If things fall apart in South Sudan, then that would make it very difficult to separate the war in Sudan from the war in South Sudan,” Alan Boswell, an expert on South Sudan and Sudan for the International Crisis Group, told Al Jazeera last year.
Boswell’s comments came shortly after the RSF declared that it had formed a rival government in regions of the west and south where it held power. That declaration included an alliance with the South Kordofan-based Sudan People’s Liberation Movement-North (SPLM-N).
Led by Abdel Aziz al-Hilu, the SPLM-N and has spent decades fighting the Sudanese military in parts of South Kordofan and Blue Nile states. Both states border South Sudan.
Sudanese leaders have long accused South Sudanese President Salva Kiir of supporting the SPLM-N and, more recently, the RSF. In response to last year’s declaration, Sudanese leaders backed South Sudanese militias to fight the SPLM-N and RSF along the border.
Notable among those militias is the SPLM-IO, which also is fighting the South Sudanese government. SPLM-IO is aligned with South Sudanese Vice President Riek Machar, a rival who Kiir imprisoned on treason charges in 2025.
South Sudan has been a key supply corridor for the RSF in its three-year fight with the SAF for control of the country, despite Sudan’s call for South Sudan to shut down that traffic.
Even as the Sudanese government has tried to shut down the RSF’s supply lines via South Sudan, it also has worked with the South Sudanese government to protect the oil infrastructure that underpins both countries’ economies.
In December 2025, South Sudanese soldiers moved into South Kordofan to protect the Heglig Oilfield, the key oil processing facility for South Sudan’s oil. South Sudan took control of the facility under a three-way agreement with the SAF and RSF that required the South Sudanese to remain neutral in Sudan’s conflict. The agreement was signed soon after RSF fighters took control of the Heglig facility and forced SAF soldiers to retreat into South Sudan.
Under the deal, the SAF and RSF agreed to withdraw from the Heglig area. The agreement was designed to avoid military confrontations around the oil facility and to ensure that it was not sabotaged or destroyed. Tribal leaders also played a role in the process.
“The primary goal is to completely neutralize the Heglig field from any combat operations,” Paul Nang, chief of staff for the South Sudan People’s Defence Forces, said in a statement to state broadcaster SSBC News at the time.
The Heglig facility “represents an economic lifeline not only for South Sudan but for Sudan as well,” he said.
