Han–Xiongnu War
In 119 BC, when the Xiongnu suffered a catastrophic defeat by the Han armies, the Chanyu moved his court (located in present-day Inner Mongolia) to another location north. This had the desired result that the Xiongnu were separated the Wuhuan people, which also prevented the Xiongnu from exacting many resources from the Wuhuan. The Han court placed the Wuhuan in tributary protection and resettled them in five northeastern commandaries, namely Shanggu, Yuyang, Youbeiping (present-day Hebei), Liaoxi, and Liaodong (present-day Liaoning). A new office, the Colonel-Protector of the Wuhuan, was established (near present-day Beijing) in order to prevent contact between the Wuhuan with the Xiongnu and to use them to monitor the Xiongnu activities. Nevertheless, the effective Han control over the Wuhuan was lacking through much of the Western Han period, since the Xiongnu had considerable military and political influence over the Wuhuan while relations between the Wuhuan and Han often remained strained at best. This can be exemplified by a situation in 78 BC, when the Xiongnu led a punitive campaign against the Wuhuan, resulting in General Fan Mingyou (范明友) leading a Han army to impede further incursions. When they learned that the Xiongnu had left by the time the army arrived, the Han court ordered Fan to attack the Wuhuan instead, killing 6000 Wuhuan men and three chieftains, since the Wuhuan had recently raided Han territory. Only in 49 AD, when 922 Wuhuan chieftains submitted during Emperor Guangwu's reign, did many of the Wuhuan tribes come under tributary system of the Han empire. The Han court provided for the Wuhuan and in return the Wuhuan tribes guarded the Han frontier against the Xiongnu and other nomadic peoples.
Xianyun
Later Chinese annals contain a number of references to the Xianyun, such as by Sima Qian (c. 145/135 – 86 BCE), Ying Shao (140-206 CE), Wei Zhao (204-273 CE), and Jin Zhuo (late 3rd–4th century CE). Without giving specific arguments, they stated that Xunyu (獯鬻) or "Xianyun" were terms that designated nomadic people who later during the Han dynasty were transcribed as "Xiongnu" (匈奴). This view was also held by the Tang dynasty commentator Sima Zhen (c. 8th century CE). Wang Guowei (1877–1927), as a result of phonetical studies and comparisons based on the inscriptions on bronze and the structure of the characters, came to the conclusion that the tribal names "Guifang" (鬼方), "Xunyu" (獯鬻), "Xianyu" (鮮虞), Xianyun, "Rong" (戎), "Di" (狄), and "Hu" (胡) given in the annals designated one and the same people, who later entered history under the name Xiongnu.