Bögü Khan

Under the third khan of the Uyghurs, the khaganate reached the height of its power. It also acquired the thing that set it apart from every other steppe state before it.

The conversion

In 762 and 763 Bögü was at Luoyang, helping the Tang against the An Lushan rebellion.^[1] There he met followers of Manichaeism. He took four of their monks into his realm to preach.^[2] He became a convert. Shortly after, he imposed the faith on his own people.^[3] He stayed in the region of Luoyang from November 762 until about February 763. His soldiers pillaged the neighbourhood. He himself visited a group of Sogdian Manichaeans there.^[4] The Chinese text of the Karabalghasun stele names the chief of the four he took home, Ruixi. It praises him as learned in the Doctrine of Light.^[4] The Manichaean clergy among the Uyghurs kept strict rules of food. By the Chinese record of 807, they ate late in the day, drank water and refused milk.^[5]

The decision was not uncontested. He met strong opposition from conservatives at his own court. He thought it necessary to legislate for the new religion’s survival.^[3] The people were organised in groups of ten. In each group one man answered for the spiritual state of the other nine. He kept up their enthusiasm and gave instruction to any who fell into sin.^[3] The opposition was a faction led by a senior official. Ruixi’s party persuaded the khan to override it and to decree that his subjects embrace the faith.^[4]

The sources do not say why he chose it. Four explanations are offered. The first is that the faith joined sophistication to the discipline a warlike people demanded.^[6] The second is that he wished to show his independence of the Tang. The Tang disliked the faith, had condemned it in 732 and permitted only non-Chinese to practise it.^[6] The third is that he wished to ally himself with the wealth and the trade of the Sogdians.^[6] The fourth is that he was sincerely moved.^[6] In 768 the Tang ordered Manichaean temples to be built, probably in Chang’an and Luoyang. Three years later it let the Uyghurs build one each at Jingzhou, Nanchang, Shaoxing and Yangzhou.^[7]

The Chinese histories do not mention the conversion at all. It was among the most important events in Uyghur history, but it had no bearing on China, and so it is absent. By contrast, the Uyghur role in one Chinese campaign of 757 is treated at length, although it was marginal to the Uyghurs. What is known of the conversion comes from the Chinese face of the Karabalghasun inscription and from Turfan documents.^[3]

The Sogdians

By then Manichaeism was regarded as a Sogdian religion. One immediate result of the conversion was a sharp rise in Sogdian influence at the Uyghur court. There had been Sogdians in the empire before, but their numbers rose significantly after 763. Their weight lay in their culture and in their skill as architects and builders. Sogdian features appear in the ruins of many buildings in Uyghur territory. They came to form something like a state within the state. Their hold on several professions gave them great power.

Wives

He married in succession two daughters of the Tang general Pugu Huai’en. Pugu Huai’en rebelled against the Tang in 764 and died the next year. He was regarded as a Chinese, though he was a descendant of the Uyghur Bugu tribe.^[8] The first, whom he had married before his accession, died in 768. Her sister became his wife in 769.^[8] The younger princess of Ningguo had escorted her elder namesake to Karabalghasun and become the concubine of his father. She was made his katun.^[8]

Death, 779

In 779 the Tang emperor Daizong died. The Sogdians advised Bögü to use the state mourning as the opportunity for an invasion of China.^[1] He agreed.^[1]

His chief minister and first cousin Tun Bagha Tarkan was against the plan. When he saw the court going the other way, he killed Bögü, together with many of his Sogdian supporters and advisers. Then he took the throne.^[1] What followed was a period of anti-Sogdian rule. It probably brought a turn away from Manichaeism and back to the older cults.

References

^ a b c d Jiu Tangshu (Old Book of Tang), juan 195
^ Karabalghasun inscription; Radloff 1894–1895, parts 1–3, pl. facing p. 290; p. 287
^ a b c d Karabalghasun inscription
^ a b c Sinor 1990, p. 330
^ Xin Tangshu (New Book of Tang), juan 217
^ a b c d Sinor 1990, p. 330–332
^ Sinor 1990, p. 332
^ a b c Sinor 1990, p. 325

Sources

Jiu Tangshu (Old Book of Tang), juan 195
Xin Tangshu (New Book of Tang), juan 217 (after Jiu Tangshu)
Karabalghasun inscription

Literature

Colin Mackerras, The Uighur Empire According to the T'ang Dynastic Histories (1972)
Peter B. Golden, An Introduction to the History of the Turkic Peoples (1992)
Étienne de la Vaissière, Sogdian Traders: A History (2005)
Emre-E. Yavuz, The Gokturk Empire: 2nd Edition (2025)
Wilhelm Radloff, Die alttürkischen Inschriften der Mongolei (1894–1895, parts 1–3)
Denis Sinor (ed.), The Cambridge History of Early Inner Asia (1990)