From the fifth century Turkic tribal groups under various names were found living beyond China’s northern borders from Korea to Central Asia. With China divided the Turks first preyed on, then conquered and ruled parts of northern China in many short lived dynasties.
With the rise of the Tang (T’ang) dynasty (618–909), the tables turned. Taizong (T’ai-tsung, r. 626–649) defeated both the Eastern and Western Turks, accepted their vassalage, and was proclaimed their heavenly khan.
The Uighurs were a branch of Turks organized into 10 clans and lived primarily a nomadic life in the steppes of Mongolia north of China. In the mid-eighth century they became the most powerful nomads in the region, and under Kaghan Ku-li p’ei-lo established an Uighur Empire, which was a client state of the Tang.
This ambiguity of status is apparent from the kaghans’ claim that they were appointed by heaven, though they simultaneously sought and received appointment to their positions from the Tang court.
A permanent capital was established at Karabalghasan in Mongolia but the Uighurs continued to live in tents and the kaghan’s palace was a large golden tent that could hold 100 people.
The Uighur state prospered under Ku-li, his son Mo-yen-ch’o (r. 747– 759), and his son Mo-yu. The An Lushan (An Lu-Shan) Rebellion (755–763) elevated the Uighurs from being vassals to useful and difficult allies of the Tang.
Kaghan Mo-ye-ch’o answered Suzong’s (Su-tsung, successor to Ming Huang, who abdicated in disgrace in 755) call for help. In 757 the Uighur cavalry arrived from Mongolia and helped recapture the Tang eastern capital Luoyang (Loyang) from the rebels.
The Tang had to pay a high price for the assistance—as agreed to beforehand the Uighurs were allowed to loot Luoyang for three days. Later in the rebellion in 762, a Sino-Uighur force retook Luoyang.
Another result of Uighur military assistance was a series of marriages between members of the two ruling houses: Members of the Li imperial clan married Uighur princesses and a total of seven principal wives (out of 13) of Uighur kaghans were Tang princesses, including three who were daughters of reigning Tang emperors (others were adopted daughters).
Uighurs continued to demand and receive costly gifts from the Tang court after the end of the rebellion and also enjoyed favorable terms of trade with the Chinese, for example receiving 40–50 bolts of silk for each horse, which was far above the fair value.
The decline of Tang power in the Western Regions also profited the Uighurs, who charged high tolls for trade goods in transit. The year 790 was the last time the Tang and Uighur armies campaigned together, against the Tibetan Kingdom, which had also grown powerful as a result of the An Lushan Rebellion.
While in Luoyang in 762 the Uighur kaghan Mou-yu converted to Manicheanism, choosing it over Buddhism and Nestorian Christianity. As a result Manicheanism became the official religion of the Uighur state.
This move was welcomed by the Tang court, which hoped that the adopting of this peaceful religion would make the Uighurs less violent. At the kaghan’s request China allowed the building of Manichean temples in Louyang and several additional important cities.
Because the Sogdians were responsible for converting the Uighurs to their religion, Sogdian influence over the Uighurs was enhanced. An alphabet, based on the Sogdian script, was created for writing Uighur, which until then had no written language.
Until this time all contemporary written knowledge about the nomads in contact with China came from Chinese sources. Many Tang government bureaus, such as the ministry of war, court of diplomatic reception, and provincial officials, gathered and kept records on the geography, customs, clothes, and products of the Uighurs and other border peoples.
Naturally they focused on how the nomads impacted on China and reflected the Chinese perspective. In the 20th century archaeologists discovered two steles in Karabalghasun and in northern Mongolia with inscriptions in three languages: Chinese, Sogdian, and Uighur. Some documents in the Uighur language have also survived, preserved in the caves of Dunhuang (Tunhuang) in western China.
Two dynasties and 13 kaghans presided over the Uighurs during their century of power; five were assassinated; several others were overthrown. Uighur politics was unstable because of tribal politics and much depended on the ability of the kaghan to maintain control over autonomous chiefs.
Social changes that resulted from increased wealth and power after the mid-eighth century undermined traditional Uighur society and economy, from nomadic to semiagricultural, and subsistence to dependence on imported luxuries. The new religion created tensions between traditionalists and Manichean converts; Manicheanism also made the Uighurs less warlike.
Aggressive neighbors, Tibetans, and especially the appearance of another group of warlike nomads called Kirghiz began to encroach on Uighur territory. In 839 a famine and pestilence hit. By 844 the Uighur state had collapsed, never to rise again.