The Uygurs made rapid socio-economic and cultural progress between the ninth and the 12th centuries. Nomadism gave way to settled farming. Commercial and trade ties with central China began to thrive better than ever before. Through markets, they exchanged horses, jade, frankincense and medicines for iron implements, tea, silk and money.
With the feudal system further established, a land and animal owners' class came into being, comprising Uygur khans and Bokes (officials) at all levels. After Islam was introduced to Kaxgar in the late 10th century, it gradually extended its influence to Shache (Yarkant) and Yutian, and later in the 12th century to Kuya and Yanqi, where it replaced Shamanism, Manichae, Jingism (Nestorianism, introduced to China during the Tang Dynasty), Ao'ism (Mazdaism) and Buddhism, which had been popular for hundreds of years. Western Region culture developed quickly, with Uygur, Han, Sanskrit, Cuili and Poluomi languages, calendars and painting styles being used.
Two major centers of Uygur culture and literature -- Turpan in the north and Kaxgar in the south -- came into being. The large number of government documents, religious books and folk stories of this period are important works for students of the Uygur history, language and culture.