Han dynasty
To the north of China proper, the nomadic Xiongnu chieftain Modu Chanyu (r. 209–174 BC) conquered various tribes inhabiting the eastern portion of the Eurasian Steppe. By the end of his reign, he controlled Manchuria, Mongolia, and the Tarim Basin, subjugating over twenty states east of Samarkand. Emperor Gaozu was troubled about the abundant Han-manufactured iron weapons traded to the Xiongnu along the northern borders, and he established a trade embargo against the group. In retaliation, the Xiongnu invaded what is now Shanxi province, where they defeated the Han forces at Baideng in 200 BC. After negotiations, the "heqin" agreement in 198 BC nominally held the leaders of the Xiongnu and the Han as equal partners in a royal marriage alliance, but the Han were forced to send large amounts of tribute items such as silk clothes, food, and wine to the Xiongnu.
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.