The Country of Kang and the Manichaeans
The country of Kang (康 kāng) was one of a group of small states in Central Asia. It was located in the area near Samarkand (present-day Uzbekistan) and came under the control of the Tang dynasty in the 8th century.
Manichaeism was founded in Persia in the 3rd century AD by Mani, who drew on several religions, including Zoroastrianism and Christianity, in creating it. Manichaeism was characterised by a dualistic view of the world as a struggle between the forces of light (the spiritual world) and darkness (the material, physical world).
It reached the western regions of present-day China by the 6th-7th century and China proper by the end of the 7th century. It was eventually banned in China but continued to exist for several centuries, becoming a force behind peasant uprisings in the 10th-12th centuries.
Most information on the web concerning Manichaeism is related to its influence on Christianity through St Augustine. For some additional information, see Zoroaster and Mani (by H. G. Wells).