SUMMARY
The Sudan People’s Liberation Movement/Army-in-Opposition (SPLM/A-IO) emerged in December 2013 as an opposition political movement and armed rebel group under the leadership of former Vice President Riek Machar. The movement split from the ruling Sudan People’s Liberation Movement/Army (SPLM/A) amid escalating political tensions between President Salva Kiir and Machar over the leadership and direction of the governing party, which had led South Sudan since independence in 2011. On 18 December 2013, Machar announced the formation of the SPLM/A-IO, stating that its objective was to remove President Kiir from power and reform the SPLM/A.
Political tensions within the SPLM/A had intensified throughout 2013 as divisions emerged over leadership, governance, and internal party reform. Rivalries between Kiir and Machar deepened after Machar publicly announced his intention to challenge Kiir for the presidency within the SPLM/A. In July 2013, Kiir dismissed Machar from his position as Vice President and dissolved the cabinet, further increasing tensions within the ruling elite and contributing to growing polarization within the SPLM/A and the armed forces. The divisions increasingly aligned along political and ethnic lines, particularly between factions associated with Kiir, who drew most of his support from the Dinka community, and those aligned with Machar, who was predominantly supported by Nuer constituencies.
The conflict began on 15 December 2013, when fighting erupted in the capital, Juba, between rival factions within the SPLA aligned with Kiir and Machar respectively. Following the clashes, President Kiir accused Machar and his allies of attempting a coup and ordered the arrest of several senior political figures. Machar denied involvement in any coup attempt and fled Juba shortly after the outbreak of violence. In the weeks that followed, several military divisions, commanders, and soldiers defected from government forces to the SPLM/A-IO. Opposition forces subsequently gained control over parts of Jonglei, Upper Nile, and Unity states, and the violence rapidly expanded into a nationwide civil war marked by large-scale displacement, ethnic violence, and widespread abuses against civilians. The conflict increasingly took on ethnic dimensions, particularly between communities associated with the Dinka, who largely supported Kiir, and the Nuer, many of whom were perceived as aligned with Machar and the SPLM/A-IO.
A series of regional and international mediation efforts led to several ceasefire agreements and peace negotiations between the SPLM/A-IO and the Government of South Sudan. These efforts culminated in the signing of the Revitalized Agreement on the Resolution of the Conflict in South Sudan (R-ARCSS) in September 2018, which provided for a permanent ceasefire, security sector reforms, and the formation of a transitional unity government. In February 2020, Riek Machar was reinstated as First Vice President under the power-sharing arrangement. Despite the agreement, implementation remained slow and tensions between the parties persisted, particularly over security arrangements, governance, and the integration of rival forces.
The conflict over government between the Government of South Sudan and SPLM/A-IO resumed in 2025 for the first time since Riek Machar becoming the First Vice President within the transitional government. The deterioration accelerated in early March following large-scale attacks in Nasir country in Upper Nile state, led by the White Army, an independent Nuer self-defense militia that has at times been loosely aligned with SPLM/A-IO but operates autonomously. Following the attacks, President Kiir arrested Machar along with several senior SPLM/A-IO political and military officials, accusing them of backing the rebellion. SPLM/A-IO rejected the accusations, denied responsibility for the Nasir violence, and declared the peace agreement effectively collapsed. Throughout the remainder of 2025, fighting between government forces and SPLM/A-IO intensified across Upper Nile, Jonglei, and parts of Equatoria.
