Succession, Civil War, and the Four Khanates

Genghis Khan died in August 1227, during or shortly after the final campaign against Xi Xia; the exact cause of his death remains uncertain, with medieval sources proposing a fall from a horse, an infected wound, or fever, and he was buried in a place kept deliberately secret, possibly near Burkhan Khaldun mountain. Before dying, he had designated as his successor his third son, Ogodei, passing over Jochi, who had died months earlier under unclear circumstances, and Chagatai and Tolui, a choice meant to avoid conflict between Jochi and Chagatai over doubts about Jochi's biological paternity. He had distributed appanages among his four sons during his lifetime: to Jochi the westernmost lands, origin of the future Golden Horde; to Chagatai, Central Asia; to Ogodei, the center; and to Tolui, the Mongol homeland along with the bulk of the army. Tolui served as interim regent for nearly two years (1227-1229) until a kurultai near the Kerulen River formally confirmed Ogodei as second Great Khan in 1229.