In 1260, the Mongol Empire reached its widest point—and then split apart within a single generation. This episode zooms in on the pivotal succession crisis that followed Möngke Khan's death, when two brothers—Khubilai and Ariq Böke—each claimed the throne. We trace how Ariq Böke, based in Karakorum, won over the kurultai with traditional rituals and the support of the Chinggisid line, while Khubilai, commanding from Kaiping, countered with his own assembly and the backing of Chinese advisors. The result was a four-year civil war that shattered the empire into the Yuan, Ilkhanate, Golden Horde, and Chagatai Khanate. We also explore the deeper structural flaws—the lack of a fixed succession law, the Yassa's ambiguity, and the tensions between steppe custom and sedentary governance—that made the split almost inevitable. Along the way, we meet key figures like Alghu, who betrayed Ariq Böke in the Chagatai lands, and we reflect on how the Mongol Peace, or Pax Mongolica, unravelled into rival khanates.