During the Northern Song, the term "Tufan" 吐蕃 referred to Tibetans living in western China. These Tibetans accepted as their king a descendant of the ancient Tufan kingdom's royal family, whose name, Rgyal sras 唃厮囉, originally meant "son of the Buddha." For about a century, he and his successors controlled the Amdo region. The Song had assigned them the responsibility of serving as a check on the Xixia 西夏, but as the Xixia became more powerful, Tuf an suffered from internal political divisions and grew weaker. Buddhism profoundly colored the history of western China's Tibetans. Their leaders had a deep faith in the religion, and monasteries flourished in Rgyal sras's capital of Qingtangcheng 青唐城 (the modern Xining 西寧), which was an important religious center. The government revered monks and even placed Buddhist images in official buildings. Buddhism also flourished among the common people, and Buddhist images were to be found in every village. As the political strength of Rgyal sras's suecessors steadily declined, monks came to power in the various regions. In the absence of central authority, tribal chieftain's became monks to maintain. their position by grasping both political and religious authority. To win over these tonsured chieftains, the Song bestowed on them the purple robe, the title of master 師號 or ordination certificates. They even established monasteries. In these ways, the Song attempted to use religion to control the Tibetan peoples of western China. Moreover, the political position of monks among these Tibetan peoples in the eleventh century became a model for Tibet's later Buddhist Kingdom.
