Chizhishizhuhou Chanyu
The southern Xiongnu were a branch of the eastern Xiongnu that followed the rebellious pretender Huhanye and in 51-53 BC moved en masse within the Han borders under protection of Chinese. Since the times of Huhanye, the status of the southern Xiongnu was loyal allies of the Han Dynasty. The southern Xiongnu enjoyed material support of the old "heqin" treaty, and in return guarded the Chinese northern borders and participated in the Chinese external and internecine conflicts as long as the Chinese court respected their independence. However, when the Han imperial court attempted to appoint an ineligible for the crown Western Jükü-Prince Yufuluo from ineligible Right Wing as a Chanyu, instead of respecting the traditional election, the southern Xiongnu dissented and elected a lawful alternate Hyuibu Gudu-heu. Later they expelled Yufuluo, who had to seek safety in exile at the Han imperial court.
Han–Xiongnu War
During the Warring States period, the Qin, Zhao, and Yan states conquered various nomadic territories inhabited by the Xiongnu and other Hu peoples. They strengthen their new frontiers with elongated wall fortifications. By 221 BC, the Qin ended the chaotic Eastern Zhou period by conquering all other states and unifying the entire nation. In 215 BC, Qin Shi Huang ordered General Meng Tian to set out against the Xiongnu tribes, situated in the Ordos region, and establish a frontier region at the Ordos Loop. Believing that the Xiongnu were a possible threat, the emperor launched a pre-emptive strike against the Xiongnu with the intention to expand his empire. Later that year (215 BC), General Meng Tian succeeded in defeating the Xiongnu and driving them from the Ordos region, seizing their territory as result. After the catastrophic defeat at the hands of Meng, Touman Chanyu and his followers fled far into the Mongolian Plateau. Fusu (Prince of Qin) and General Meng Tian were stationed at a garrison in Suide and soon began with the construction of the walled defenses, connecting it with the old walls built by Qin, Yan and Zhao states. The fortified walls ran from Liaodong to Lintao, thus enclosing the conquered Ordos region, safeguarding the Qin empire against the Xiongnu and other northern nomadic people. Due to the northward expansion, the threat that the Qin empire posed to the Xiongnu ultimately led to the state formation of the many tribes towards a confederacy.