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.
Noin-Ula burial site
Despite the aforementioned excavated Noin-Ula portrait indicating Mongoloid lineage of the Xiongnu, Euro-centric observers of Xiongnu culture and history try to place the Xiongnu people in a non-Mongoloid or non-Asian ancestry or descendancy. Among the most important artifacts from Noin-Ula are embroidered portrait images. These shed light on the ethnicity of the Xiongnu, albeit controversially. It has been claimed that the portraits depict Greco-Bactrians, or are Greek depictions of Scythian soldiers from the Black Sea. Such suggestions are far-fetched. There are several historical sources confirming the appearance of the Xiongnu. In 350 AD, for example, power in the South Xiongnu state of Chjao (Pin. "Zhao") was seized by a usurper, a Chinese named Shi Min, who ordered all the Xiongnu in the state exterminated; in the slaughter "many Chinese with prominent noses" died, suggesting the Xiongnu had "prominent noses" compared to those of the Chinese. In the famous Chinese bas-relief "Fight on the bridge" the mounted Xiongnu are shown with big noses. A skull analysis of Xiongnu burials made by G.F. Debets found a distinct Paleo-Siberian type of Asian facial appearance with "not a flat, but with not strongly protruding nose", somewhat similar to some North American Indians. This type is represented on the embroidery from Noin-Ula. What to the rest of the Chinese looked like a high nose, to the Europeans looked like a flat nose.