During the Northern Zhou Dynasty, Datong began to be called Yunzhong. After the Sui Dynasty unified China, the state was changed to county, and Datong became the land of Mayi County and Yanmen County. Later, the Turks invaded, and Datong became the military frontier. Until the Tang Dynasty, this place was in dire straits. At the end of the Tang Dynasty, during the separatist period, Yunzhou was caught in a long-term war. The land of the Five Dynasties was occupied by the later Tang Dynasty, and the division did not change much. After that, Shi Jingtang defected, intending to cede Datong area to Qidan. Although it was hard to defend the city, I finally contributed. After that, Datong was ruled by Khitan, Nuzhen and Mongolian rulers for 433 years, which made the Han nationality in the Central Plains lose their northern screen.