Suyab and Talas in modern-day Kyrgyzstan were the main Sogdian centers in the north that dominated the caravan routes of the 6th to 8th centuries. Their commercial interests were protected by the resurgent military power of the Göktürks, whose empire was built on the political power of the Ashina clan and economic clout of the Sogdians. Sogdian trade, with some interruptions, continued into the 9th century. For instance, camels, women, girls, silver, and gold were seized from Sogdia during a raid by Qapaghan Qaghan (692–716), ruler of the Second Turkic Khaganate. In the 10th century Sogdiana was incorporated into the Uighur Empire, which until 840 encompassed northern Central Asia. This khaganate obtained enormous deliveries of silk from Tang China in exchange for horses, in turn relying on the Sogdians to sell much of this silk further west. Peter B. Golden writes that the Uyghurs not only adopted the writing system and religious faiths of the Sogdians, such as Manichaeism, Buddhism, and Christianity, but also looked to the Sogdians as "mentors" while gradually replacing them in their roles as Silk Road traders and purveyors of culture. Muslim geographers of the 10th century drew upon Sogdian records dating to 750–840. After the end of the Uyghur Empire, Sogdian trade underwent a crisis. Following the Muslim conquest of Transoxiana in the 8th century, the Samanids resumed trade on the northwestern road leading to the Khazars and the Urals and the northeastern one toward the nearby Turkic tribes.