In the 1260s, the Mongol Empire tore itself apart from within. This episode focuses on the war between Berke Khan of the Golden Horde and Hulegu of the Ilkhanate—a conflict that shattered the unity Chinggis Khan built. We explore the Battle of the Terek River (1262), where Mongol fought Mongol for the first time in open battle. Why did Berke, a Muslim convert, ally with the Mamluk sultan Baybars against his own cousin? How did the murder of Berke's Jochid relatives in Baghdad and the Ilkhanate's alliance with the Mamluks turn trade routes into battlefields? We also examine the economic fallout: the Silk Road fractured, the yam system broke down, and the ortogh merchant networks collapsed. This war didn't just split the empire—it reshaped Central Asia, the Middle East, and Europe for centuries. Names and terms you'll hear: Berke, Hulegu, Terek River, Baybars, Mamluk Sultanate, Golden Horde, Ilkhanate, Jochid, Toluid, Chinggisid, Yassa, yam, ortogh, Caucasus, Tabriz, Sarai.