Armed conflicts often involve multiple factions, and research has shown these dynamics can lead to defections under specific conditions. While much attention has focused on opposition group defections, there is limited exploration of defections from government-aligned militias, particularly pro-government militias (PGMs). This chapter examines PGMs in Sudan, where peace negotiations often threaten their political and material interests, compelling them to resist processes that disrupt the status quo of conflict. PGMs, often remnants of colonial strategies employing local militias for control, act as “spoilers” when excluded from peace processes or perceive threats to their autonomy and benefits. The April 2023 conflict in Sudan highlights this dynamic. A standoff between the Sudanese Armed Forces (SAF) and the Rapid Support Forces (RSF) over military integration escalated into a civil war, engulfing Khartoum and spreading nationwide. The RSF, which evolved from the Janjaweed militia, defected due to disputes over power-sharing and perceived threats to its autonomy. Using rationalist theories of war, this chapter explores how government missteps heighten the likelihood of defection, such as failing to grant concessions to PGMs. This case demonstrates that PGMs can undermine peacebuilding efforts when their interests are excluded or dismissed, highlighting the importance of addressing intra-government divisions during peace negotiations. Ultimately, sustainable peace requires acknowledging the complex interplay between state and militia actors, as demonstrated by Sudan’s ongoing conflict.