Ordos Plateau
In Chinese accounts, the Xiongnu first appear at Ordos in the "Yizhoushu" and "Shanhaijing" during the Warring States period before it was occupied by Qin and Zhao. It is generally thought to be their homeland, however when exactly they came to occupy the region is unclear, and it might have been much earlier than traditionally thought, as suggested by archaeological finds. As the Xiongnu expanded southward into Yuezhi territory around 160 BC under their leader Modun, the Yuezhi in turn defeated the Sakas (Scythians) and pushed them away at the Issyk Kul. It is thought the Xiongnu also occupied the Ordos area during the same period, when they came in direct contact with the Chinese. From there, the Xiongnu conducted numerous devastating raids into Chinese territory (167, 158, 142, 129 BC). The Han Dynasty started to fight the Xiongnu in the 2nd century BC under emperor Han Wudi, and colonized the area of the Ordos under Shuofang commandery in 127 BC. Prior to the campaign, there were already commanderies established earlier by Qin and Zhao until they were overrun by the Xiongnu in 209 BC.
Xiongnu
As a result of these battles, the Chinese controlled the strategic region from the Ordos and Gansu corridor to Lop Nor. They succeeded in separating the Xiongnu from the Qiang peoples to the south, and also gained direct access to the Western Regions. Because of strong Chinese control over the Xiongnu, the Xiongnu became unstable and were no longer a threat to the Han Chinese.
Ban Chao, Protector General (都護; "Duhu") of the Han dynasty, embarked with an army of 70,000 men in a campaign against the Xiongnu insurgents who were harassing the trade route now known as the Silk Road. His successful military campaign saw the subjugation of one Xiongnu tribe after another. Ban Chao also sent an envoy named Gan Ying to Daqin (Rome). Ban Chao was created the Marquess of Dingyuan (定遠侯, i.e., "the Marquess who stabilized faraway places") for his services to the Han Empire and returned to the capital Luoyang at the age of 70 years and died there in the year 102. Following his death, the power of the Xiongnu in the Western Regions increased again, and the emperors of subsequent dynasties were never again able to reach so far to the west.