Xiongnu
Full-scale war broke out in autumn 129 BC, when 40,000 Chinese cavalry made a surprise attack on the Xiongnu at the border markets. In 127 BC, the Han general Wei Qing retook the Ordos. In 121 BC, the Xiongnu suffered another setback when Huo Qubing led a force of light cavalry westward out of Longxi and within six days fought his way through five Xiongnu kingdoms. The Xiongnu Hunye king was forced to surrender with 40,000 men. In 119 BC both Huo and Wei, each leading 50,000 cavalrymen and 100,000 footsoldiers (in order to keep up with the mobility of the Xiongnu, many of the non-cavalry Han soldiers were mobile infantrymen who traveled on horseback but fought on foot), and advancing along different routes, forced the "chanyu" and his court to flee north of the Gobi Desert. Major logistical difficulties limited the duration and long-term continuation of these campaigns. According to the analysis of Yan You (嚴尤), the difficulties were twofold. Firstly there was the problem of supplying food across long distances. Secondly, the weather in the northern Xiongnu lands was difficult for Han soldiers, who could never carry enough fuel. According to official reports, the Xiongnu lost 80,000 to 90,000 men, and out of the 140,000 horses the Han forces had brought into the desert, fewer than 30,000 returned to China.
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".