Jin dynasty (1115–1234)
Fall of Jin

Starting from the early 13th century, the Jin dynasty began to feel the pressure of Mongols from the north. Genghis Khan first led the Mongols into Western Xia territory in 1205 and ravaged it four years later. In 1211 about 50,000 Mongol horsemen invaded the Jin Empire and began absorbing Khitan and Jurchen rebels. The Jin had a large army with 150,000 cavalry but abandoned the "western capital" Datong (see also the Battle of Yehuling). The next year the Mongols went north and looted the Jin "eastern capital", and in 1213 they besieged the "central capital", Zhongdu (present-day Beijing). In 1214 the Jin made a humiliating treaty but retained the capital. That summer, Emperor Xuanzong abandoned the central capital and moved the government to the "southern capital" Kaifeng, making it the official seat of the Jin dynasty's power.

In 1216, a hawkish faction in the Jin imperial court persuaded Emperor Xuanzong to attack the Song dynasty, but in 1219 they were defeated at the same place by the Yangtze River where Wanyan Liang had been defeated in 1161. The Jin dynasty now faced a two front war that they could not afford. Furthermore, Emperor Aizong won a succession struggle against his brother and then quickly ended the war and went back to the capital. He made peace with the Tanguts of Western Xia, who had been allied with the Mongols.

The Jurchen Jin emperor Wanyan Yongji 's daughter, Jurchen Princess Qiguo was married to Mongol leader Genghis Khan in exchange for relieving the Mongol siege of Zhongdu in the Mongol conquest of the Jin dynasty.

Many Han Chinese and Khitans defected to the Mongols to fight against the Jin dynasty. Two Han Chinese leaders, Shi Tianze and Liu Heima, and the Khitan Xiao Zhala defected and commanded the three tumens in the Mongol army. Liu Heima and Shi Tianze served Genghis Khan's successor, Ögedei Khan. Liu Heima and Shi Tianxiang led armies against Western Xia for the Mongols. There were four Han tumens and three Khitan tumens, with each tumen consisting of 10,000 troops. The three Khitan generals Shimo Beidi'er, Tabuyir, and Xiao Zhongxi (Xiao Zhala's son) 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.

Shi Tianze was a Han Chinese who lived under Jin rule. Inter-ethnic marriage between Han Chinese and Jurchens became common at this time. His father was Shi Bingzhi. Shi Bingzhi married a Jurchen woman (surname Nahe) and a Han Chinese woman (surname Zhang); it is unknown which of them was Shi Tianze's mother. Shi Tianze was married to two Jurchen women, a Han Chinese woman, and a Korean woman, and his son Shi Gang was born to one of his Jurchen wives. His Jurchen wives' surnames were Monian and Nahe, his Korean wife's surname was Li, and his Han Chinese wife's surname was Shi. Shi Tianze defected to the Mongol forces upon their invasion of the Jin dynasty. His son, Shi Gang, married a Keraite woman; the Keraites were Mongolified Turkic people and considered as part of the "Mongol nation". Shi Tianze, Zhang Rou, Yan Shi and other Han Chinese who served in the Jin dynasty and defected to the Mongols helped build the structure for the administration of the new Mongol state.

The Mongols created a Han army out of defecting Jin troops, and another army out of defected Song troops called the "Newly Submitted Army" (新附軍).

Genghis Khan died in 1227 while his armies were attacking Western Xia. His successor, Ögedei Khan, invaded the Jin dynasty again in 1232 with assistance from the Southern Song dynasty. The Jurchens tried to resist; but when the Mongols besieged Kaifeng in 1233, Emperor Aizong fled south to the city of Caizhou. A Song–Mongol allied army surrounded the capital, and the next year Emperor Aizong committed suicide by hanging himself to avoid being captured in the Mongols besieged Caizhou, ending the Jin dynasty in 1234. The territory of the Jin dynasty was to be divided between the Mongols and the Song dynasty. However, due to lingering territorial disputes, the Song dynasty and the Mongols eventually went to war with one another over these territories.
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