Sudan’s war, now in its second calendar year, has moved beyond episodic battles and into a strategic phase in which territorial control, supply lines and patronage networks determine the shape of any durable settlement. The army’s January 2025 advances in central Sudan — including the retaking of Wad Madani — underscore a shifting battlefield balance that could produce durable zones of control rather than a quick national reconciliation. These shifts matter because they change who controls stockpiles, bases and the routes used to move materiel across borders.

The pattern of arms transfers feeding the conflict is not a simple bilateral flow from exporters to end users. Investigations in 2024 documented a steady influx of recently manufactured small arms and ammunition into Sudan, often routed through opaque commercial channels and then redistributed inside the country. Those flows have expanded the variety and lethality of weapons in circulation, increasing the chance that modern rifles and ammunition will leave battlefields and cross porous frontiers.

Outside actors and regional logistics have amplified the problem. Reporting and imagery from late 2024 identified a surge in cargo flights into the Chad-Sudan border area that international monitors and western officials assessed as carrying materiel benefiting Sudanese paramilitary forces. Such air bridges and third-country transit points are classic multipliers: they replenish frontline arsenals, sustain prolonged offensives and create new opportunities for diversion and illicit resale.

For South Sudan the risk is acute and twofold. First, spillover of looted or diverted weapons into northern South Sudan and the contested Abyei area will change local calculations of force and deterrence. More capable small arms and scoped rifles have already been reported in border zones and in civilian hands in the latter half of 2024, which elevates the lethality of communal clashes and weakens the protective value of existing peace arrangements. Second, political friction generated by cross-border incidents — for example the reported killings of South Sudanese nationals in Wad Madani and subsequent unrest in Juba — can rapidly convert security anxieties into interstate mistrust and domestic instability.

These dynamics interact with long standing structural vulnerabilities. Northern Bahr el Ghazal, Abyei and adjacent counties already host informal barter economies in which fuel, food and livestock move in exchange networks that also carry people and kit. When combatants or criminal networks exploit these routes, weapons flow becomes part of the same shadow economy that sustains cross-border livelihoods and patronage. That makes interdiction politically sensitive and operationally difficult.

Any credible analysis of partition scenarios must therefore treat arms flows as central, not incidental. A de facto partition that hardens into separate SAF-dominated and RSF-dominated zones would leave multiple, competing arsenals within reach of neighbouring states and nonstate actors. Those arsenals will be replenished through formal and informal avenues, with external patrons able to sustain proxies and local brokers able to monetise looted materiel. Over time this raises the prospect of South Sudan becoming a corridor, refuge and secondary market for weapons, with consequences for the 2018- era peace frameworks and for UN and African Union stabilization efforts.

Policy choices now will shape whether spillover becomes episodic or systemic. Practical steps that can be taken with limited political cost include: strengthening joint border monitoring between Juba and Khartoum under AU or UN auspices; prioritising forensic tracing of seized weapons to identify diversion chains; harmonising export control and aviation transparency measures with regional partners to constrain air and land transit routes; and increasing support for civil protection in vulnerable border communities to reduce incentives for arms accumulation. These measures will not eliminate the problem but they raise the cost and reduce the profitability of cross-border arms trafficking.

Longer term, donors and regional powers must recognise that an induced partition increases the political return on supplying proxies and that permissive supply chains will therefore persist unless those returns are reduced. That requires concomitant levers: sanctions on entities and logistics chains credibly linked to diversion; conditional engagement with state and nonstate patrons that ties reconstruction or oil transit cooperation to concrete disarmament and stockpile safeguards; and persistent investment in local conflict mitigation that addresses the economic drivers of illicit trade. The African Union’s public condemnation of violence against South Sudanese nationals is a reminder that regional political signalling matters and can be used to build a coalition for enforcement if it is backed by practical, verifiable steps.

The strategic calculus for policymakers in Juba, Khartoum and in capitals of regional partners is straightforward. A Sudan that fragments into semi-permanent fiefdoms will be a long-term source of instability for the region. Arms spillover into South Sudan is not a distant, abstract risk. It is a present hazard that is already manifesting in seizures, disruptions to trade and episodes of communal violence and political unrest. The policy imperative is to make diversion harder, reduce the demand for illicit weapons at the community level, and tie any reconstruction or commercial cooperation to robust safeguards on arms and logistics. If those steps are not taken, partition will not only redraw maps inside Sudan; it will rearm and deepen conflicts across its borders for years to come.