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.
Origin of the Huns
There is a gap of about two hundred years between the conquest of the Xiongnu by the Xianbei and their disappearance from Chinese historical records and the appearance of the Huns in Greco-Roman sources. According to the "Book of the Later Han", the final known Xiongnu emperor either disappeared to the west or moved to the territory of the Wusun in modern Kazakhstan in 91. According to the "Wei shu", they then moved further west to around modern Tashkent, where they were defeated by the Xianbei in 153after this, nothing further is recorded about them for twocenturies.
Denis Sinor argued that the origins of the Huns cannot be established beyond what it is said in the work of Roman historian Ammianus Marcellinus: Ammianus said that the Huns dwelled beyond the Sea of Azov next to "the frozen ocean" before they entered Europe, though Sinor does not take "frozen ocean" literally. Both he and Maenchen-Helfen, meanwhile, note that Ammianus refers to the Huns having been "little known", not unknown, before they appeared in 370: they connect this with a mention of a people called the "Khounoi" by the geographer Ptolemy in the mid-second century. Maenchen-Helfen notes, moreover, that the fact that the Huns were not noticed before 370 is not proof that they came from far away, comparing them to the ancient Hungarians: "We know by now that the Magyars (Hungarians) lived for three hundred years practically unnoticed by the Byzantines in the region of the Dnieper, Bug, Dniester, Pruth, and Sereth before they swept over Central Europe very much like the Huns".