After Qin Shihuang unified China, in 2 14, he ordered Meng Tian to lead 300,000 Qin Jun to attack Xiongnu in the north, collect Hetao and station troops in the county (now southeast of Yulin City, Shaanxi Province). "But the Huns were more than 700 miles away, and the Hu people dared not go south to herd horses" (On Qin). Meng Tian built a fortress from Yuzhong (now Gansu) along the Yellow River to Yinshan Mountain, connecting the old Great Wall of more than 5,000 miles in Qin, Zhao and Yan, winding up on Yangshan Mountain (north of Yinshan Mountain) to the north, Jiuyuan to the north and Yunyang to the south, building a straight highway and forming a long defense line in the north. Meng Tian stayed in the north for more than ten years, but the Huns were too scared to do it again.
The Han Dynasty fought many large-scale wars with the Huns. In the early Han Dynasty 20 1 years ago, Han Wangxin was forced to surrender to the Huns. The following year, Emperor Gaozu Liu Bang led a 320,000-strong army to conquer and was besieged by more than 400,000 cavalry in Deng Bai (now northeast of Datong) for 7 days and nights. The siege of Deng Baishan is still controversial. As a bloody and cold-blooded person, Morton is unlikely to let a huge enemy go because of a few words from a woman. There is also a saying that it was because the frequency corps arrived in time, and the Huns agreed to retreat when they saw that the Han reinforcements were not sure of winning. Later, the Han Dynasty adopted Liu Jing's suggestion, implemented a "pro-marriage policy" towards the Huns, married Han women and Khan, gave them 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 reign of Emperor Wu of the Han Dynasty, after nearly 70 years of recuperation, the economy and national strength of the Western Han Dynasty were greatly enhanced, and three wars were launched against Xiongnu from strategic defense to strategic attack: the battle of Henan (also known as the battle of Monan), the battle of Hexi and the battle of Mobei. At this time, it was the time when Khan was in office.
/kloc-before 0/27, Emperor Wu of the Han Dynasty sent Wei Qing to recover Henan. 12 1 years ago, Emperor Wu of the Han Dynasty sent Huo Qubing to seize the Hexi Corridor, surrendered 100,000 Huns on the right, and set up four counties: Wuwei, Jiuquan, Dunhuang and Zhangye. 1 19 ago, Wei Qing and Huo Qubing led fifty thousand cavalry to attack in two ways. Wei Qing was defeated by Khan, and Huo Qubing left more than seventy thousand troops to seal the wolf in Xuzhou. The two armies annihilated more than 90,000 Huns, making it impossible to cross the desert south for a while.
The decline and fall period of Xiongnu was from an oblique Khan to Uhaanyehe, as Khan experienced 18, from Ding Yuan, Emperor Wu of Han Dynasty, to Zhao Jian, Emperor Wu of Han Dynasty (the first 36 years).