Violence across the Sudan–South Sudan–Central African Republic (CAR)–Democratic Republic of the Congo (DRC) borderlands cannot be understood as a set of discrete national conflicts. Armed groups operate within a regional system in which survival depends on the ability to exploit borders, navigate uneven state capacity, and embed themselves in transnational networks of trade, migration, and sanctuary. The concept of borderland regionalisation captures how these dynamics produce a connected conflict space rather than isolated crises. Situated within debates on regional conflict systems, borderland political economy, and state formation, the manuscript examines how cross-border dynamics sustain armed mobilisation. Focusing on the Sudan–South Sudan–CAR–DRC nexus, the study addresses three interrelated questions: how armed groups sustain themselves through cross-border resource extraction, arms acquisition, and access to safe havens, and what this reveals about the regional political economy of conflict; how state actors—particularly Sudan, Uganda, and the CAR government—manage, enable, or suppress armed groups for strategic purposes; and under what conditions regional mechanisms, including IGAD, ICGLR, and the African Union, effectively address cross-border conflict dynamics versus becoming arenas for competing state interests. Methodologically, the study combines regional political economy mapping using UN Panel of Experts reports, ACLED conflict data, and small arms trafficking documentation (SAS), with case studies of the Lord’s Resistance Army (LRA), Murle armed groups, and Rizeigat militias as cross-border actors. It further incorporates interviews with IGAD and ICGLR officials and network analysis of transnational supply chains. The findings show, first, that armed gr