Civil wars marked by fragmentation often generate new armed actors rather than consolidate existing ones. In South Sudan, the rapid proliferation of factions reflects not only elite political disputes but also the incentives facing local commanders embedded in war economies and systems of recognition. The concept of competitive fragmentation captures how these dynamics drive the multiplication of armed groups beyond the logic of formal political negotiation. Moving beyond a descriptive account, the manuscript situates armed group proliferation within broader debates on African political order, state formation, and institutional design. Focusing on South Sudan, with comparative reference to other fragmented civil wars, the study addresses three interrelated questions: what explains the expansion from two principal belligerents in 2013 to more than 40 registered armed groups by 2018, and what this reveals about the internal political economy of rebellion; how local commanders’ economic interests—particularly control over cattle, gold, teak, and humanitarian supply chains—drive fragmentation independently of national-level negotiations; and under what conditions international recognition, through peace agreement inclusion, DDR registration, or humanitarian engagement, inadvertently incentivises the formation of new armed actors. Methodologically, the study combines original armed group dataset construction using UNMISS monitoring reports and ACLED data (2013–2023), process tracing of key fragmentation episodes, interview-based research with commanders from seven armed groups across Greater Upper Nile and Equatoria, and the application of agent-based modelling to simulate fragmentation dynamics. The contribution lies in explaining how fragmentation is not merely a symptom o