From 629 to 648, a reunited China--under the Tang Dynasty (A.D. 618-906)--destroyed the power of the Eastern Türk north of the Gobi established suzerainty over the Kitan, a semi-nomadic Mongol people who lived in areas that became the modern Chinese provinces of Heilongjiang and Jilin and formed an alliance with the Uighurs (see Glossary), who inhabited the region between the Altai Mountains and Lake Balkash. Between 641 and 648, the Tang conquered the Western Türk, reestablishing Chinese sovereignty over Xinjiang and exacting tribute from west of the Pamir Mountains. The Türk empire finally ended in 744.

For more than a century, the Tang retained control of central and eastern Mongolia and parts of Inner Asia. During this century, the Tang expanded Chinese control into the Oxus Valley. At the same time, their allies and nominal vassals, the Uighurs, conquered much of western and northern Mongolia until, by the middle of the eighth century, the Uighur seminomadic empire extended from Lake Balkash to Lake Baykal.

It was at about this time that the Arab-led tide of Islam reached Inner Asia. After a bitter struggle, the Chinese were ejected from the Oxus Valley, but with Uighur assistance they defeated Muslim efforts to penetrate into Xinjiang. The earliest Mongol links with Tibetan Buddhism, or Lamaism (see Glossary), also may have been established in this period (see Religion , ch. 2). During this time, the Kitan of western Manchuria took advantage of the situation to throw off Chinese control, and they began to raid northern China.

Despite these crippling losses, the Tang recovered and, with considerable Uighur assistance, held their frontiers. Tang dependence upon their northern allies was apparently a source of embarrassment to the Chinese, who surreptitiously encouraged the Kirghiz and the Karluks to attack the Uighurs, driving them south into the Tarim Basin. As a result of the Kirghiz action, the Uighur empire collapsed in 846. Some of the Uighurs emigrated to Chinese Turkestan (the Turpan region), where they established a flourishing kingdom that freely submitted to Chinggis Khan several centuries later (see Early Wars in China , this ch.). Ironically, this weakening of the Uighurs undoubtedly hastened the decline and fall of the Tang Dynasty over the next fifty years.

Data as of June 1989