In the Han Dynasty, after being defeated by the Huns, East Lake retreated to the Fifth Ring Mountain and Xianbei Mountain, which were divided into the Fifth Ring Road and Xianbei Mountain. After being conquered by Cao Cao, Wu Huan declined and Xianbei clan rose. Xianbei in the Western Jin Dynasty was mainly divided into Duan, Murong, Tuoba and Rouran. Among them, Rouran fought many times with the Tuoba nationality of the Northern Wei Dynasty who ruled the northern part of the Central Plains during the Southern and Northern Dynasties. Rouran was defeated by the Turkic people and divided into two branches: north and south. Rounan Branch fled to the upper reaches of Liaohe River and became the ancestor of Qidan people. The northern branch fled to the east of Ya Blauf Mountains and south of the outer Xing 'an Mountains, and was the ancestor of Shiwei.
The Book of Old Tang Dynasty contains ten flavors of Wu Meng. Wu Meng and Mongolia are different translations of the same name, and Mongolian means "eternal flame".
Among the ministries of Mongolia, Dongmeng comes from the ministries of Shiwei and is a direct descendant of Genghis Khan's family. During the Song Dynasty, the rule of the Turkic people on the Mongolian plateau gradually declined, and the eastern Shiwei departments, including Genghis Khan's ancestors, began to migrate westward to the hinterland of the Mongolian plateau. The ministries of Shiwei are called Tatars in Turkic. The western Mongolian ministries were formed on the basis of Turkic or Turkic tribes in the same period.
In the Ming Dynasty, East Mongolia and West Mongolia were called Tatar and Wala respectively.