Division of the Mongol Empire

The division of the Mongol Empire began after Möngke Khan died in 1259 in the siege of Diaoyu Castle with no declared successor, precipitating infighting between members of the Tolui family line for the title of khagan that escalated into the Toluid Civil War. This civil war, along with the Berke–Hulagu war and the subsequent Kaidu–Kublai war, greatly weakened the authority of the great khan over the entirety of the Mongol Empire, and the empire fractured into four khanates: the Golden Horde in Eastern Europe, the Chagatai Khanate in Central Asia, the Ilkhanate in Iran, and the Yuan dynasty in China based in modern-day Beijing—although the Yuan emperors held the nominal title of khagan of the empire.

Source: Wikipedia — Division of the Mongol Empire (CC BY-SA 4.0)