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
In 53 BC Huhanye (呼韓邪) decided to enter into tributary relations with Han China. The original terms insisted on by the Han court were that, first, the "chanyu" or his representatives should come to the capital to pay homage; secondly, the "chanyu" should send a hostage prince; and thirdly, the "chanyu" should present tribute to the Han emperor. The political status of the Xiongnu in the Chinese world order was reduced from that of a "brotherly state" to that of an "outer vassal" (外臣). During this period, however, the Xiongnu maintained political sovereignty and full territorial integrity. The Great Wall of China continued to serve as the line of demarcation between Han and Xiongnu.