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.
Jiangqu
In 51 BCE a pretender to the Xiongnu's throne Huhanye re-established the "heqin" peace and kinship treaty with the Han empire, and fled to China with a fraction of the Xiongnu, partitioning the Xiongnu state into the Northern Xiongnu and Southern Xiongnu, and establishing a new polity allied with China. The Southern Xiongnu retained a title "Chanyu" for their leader, and started a new dynastic line beginning with Huhanye. Huhanye himself belonged to the 8th generation of the Maodun line of the dynastic paternal Luanti tribe, the tribe Qiang ("Kiyan") was a maternal dynastic tribe of the Southern Xiongnu. During the existence of the Southern Xiongnu state, its Xiongnu population greatly varied depending on the events in the steppe, at times it was swelling with numerous Xiongnu tribes fleeing trouble events, and at times it was losing Xiongnu tribes when they returned after return of peaceful times. The Chinese policies also affected the in and out flows. Until the event with Zhang Xiu in 179 CE, the Southern Xiongnu continued electing their Chanyus without explicit Chinese intervention, Jiangqu was the first Southern Xiongnu Chanyu who broke the traditional Xiongnu succession laws, undermining the integrity of the Southern fraction. Tribes that did not want to recognise a non-eligible leader either revolted against him, or left the area under his control.