The Xiongnu clan began to develop in the Qin Dynasty, and was unprecedentedly powerful before Emperor Wu of the Han Dynasty. Emperor Wu of the Han Dynasty sent troops to conquer many times, and the Xiongnu forces gradually weakened. In the early Western Han Dynasty, it became powerful and invaded the border many times. It posed a powerful threat to the Western Han regime. And control the western region. Later, he was defeated by Emperor Wu of the Western Han Dynasty, retreated to Mobei and split into five parts. During the Han and Yuan Dynasties, he divided Xie Han and his relatives into five parts. Later, in the Eastern Han Dynasty, it was divided into the northern and southern Xiongnu, and the southern Xiongnu surrendered to the Han Dynasty. After the westward migration, the northern Xiongnu disappeared into China's ancient books.
Huns are mostly distributed in the desert. Their tactics are to change places with one shot, harass the border all the year round and obtain living resources. The Han Dynasty adopted Liu Jing's suggestion and adopted a "pro-marriage policy" towards the Huns. The Han people married Khan, gave him some property, opened the market and allowed people from both sides to trade. In the later period, the emperors of the Jing Dynasty also followed the policy of hiding their relatives. But the Huns were still not satisfied and sent troops to invade the border from time to time.
During the Three Kingdoms period, the Huns were also hit and split, which led to their weaker strength. During the Three Kingdoms period, Cao Cao divided the Xiongnu into five parts: left, right, south, north and middle, which were assigned to Shaanxi, Shanxi and Hebei respectively. The most important person in each department is Shuai, who later changed his name to surname, and the Han people supervised and controlled it as Sima.