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Background

Genghis Khan united the Mongol tribes of the steppes and became Great Khan in 1206. He and his successors expanded the Mongol empire across Asia. Under the reign of Genghis' third son, Ögedei Khan, the Mongols destroyed the weakened Jin dynasty in 1234, conquering most of northern China. Ögedei offered his nephew Kublai a position in Xingzhou, Hebei. Kublai was unable to read Chinese but had several Han teachers attached to him since his early years by his mother Sorghaghtani. He sought the counsel of Chinese Buddhist and Confucian advisers. Möngke Khan succeeded Ögedei's son, Güyük, as Great Khan in 1251. He granted his brother Kublai control over Mongol held territories in China. Kublai built schools for Confucian scholars, issued paper money, revived Chinese rituals, and endorsed policies that stimulated agricultural and commercial growth. He adopted as his capital city Kaiping in Inner Mongolia, later renamed Shangdu.

Many Han Chinese and Khitan defected to the Mongols to fight against the Jin. Two Han Chinese leaders, Shi Tianze, Liu Heima (劉黑馬, aka Liu Ni), and the Khitan Xiao Zhala (蕭札剌) defected and commanded the 3 Tumens in the Mongol army. Liu Heima and Shi Tianze served Ögedei Khan. Liu Heima and Shi Tianxiang led armies against Western Xia for the Mongols. There were 4 Han Tumens and 3 Khitan Tumens, with each Tumen consisting of 10,000 troops. The three Khitan Generals Shimobeidier (石抹孛迭兒), Tabuyir (塔不已兒), and Zhongxi, the son of Xiaozhaci (蕭札刺之子重喜) commanded the three Khitan Tumens and the four Han Generals Zhang Rou, Yan Shi, Shi Tianze, and Liu Heima commanded the four Han tumens under Ögedei Khan.

Möngke Khan commenced a military campaign against the Chinese Song dynasty in southern China. The Mongol force that invaded southern China was far greater than the force they sent to invade the Middle East in 1256. He died in 1259 without a successor at the Siege of Diaoyucheng. Kublai returned from fighting the Song in 1260 when he learned that his brother, Ariq Böke, was challenging his claim to the throne. Kublai convened a kurultai in Kaiping that elected him Great Khan. A rival kurultai in Mongolia proclaimed Ariq Böke Great Khan, beginning a civil war. Kublai depended on the cooperation of his Chinese subjects to ensure that his army received ample resources. He bolstered his popularity among his subjects by modeling his government on the bureaucracy of traditional Chinese dynasties and adopting the Chinese era name of Zhongtong. Ariq Böke was hampered by inadequate supplies and surrendered in 1264. All of the three western khanates (Golden Horde, Chagatai Khanate and Ilkhanate) became functionally autonomous, and only the Ilkhans truly recognized Kublai as Great Khan. Civil strife had permanently divided the Mongol Empire.