In AD 47, Southern Xiongnu(南匈奴) that was formed centering on the group that moved south around the Great Wall of China lived separately after the division of Xiongnu and served as the defender of Han(漢) Dynasty. After that, Xianbi(鮮卑) tribe became powerful after the collapse of Northern Xiongnu(北匈奴) in AD 91, so many groups of Xiongnu from Mongol steppe migrated to the northern area of Great Wall of China. Due to that reason, the area of Great Wall of China was in confusion due to conflicts between various ethnic groups but it was increasingly stabilized. Southern Xiongnu, which was developed by Han Dynasty`s support and formed its power, gave rise to an internal conflict again in the late 2nd century, so key forces including Shanyu(單于) group mostly migrated to counties by centering on He-Dong(河東) province while other groups moved several provinces by centering on Bing-Zhou(幷州) province. In addition, chaotic states such as Bandits of Yellow flag(Huang-jin-Zei, 黃巾賊)`s uprising in the 180s and northern immigrants who moved south were made so that Southern Xiongnu caused inner divisions again and the key force group expelled from their stronghold held their own ground by uniting with Yuan-Shao(袁紹), but finally was controlled by Cao-Cao(曹操) who took the northern part. After that, Xiongnu failed to form the big power and was under the control of Bing-Zhou and He-Dong province. Later, Xiongnu lived in Bing-Zhou province in better environment than the edge of north by farming instead of Chinese people who moved south in the Later Han Dynasty. Cao-Cao, a person in power, firstly separated Shanyu from their own tribe and weakened power and at the same time divided groups to live separately. The control of each group was given to the own heads, so Xiongnu who lived in Bing-Zhou province was divided but many town heads were internally developed on behalf of Shanyu`s power. Like this, Cao-Cao`s controlling of Xiongnu aimed to stabilize them that was the mounted army with excellent military ability during the situation of unification war and to smoothly mobilize it. When clan of Si-Ma came to power in the late Cao-Wei Dynasty, Liu-Bao(劉豹), a chief of Xiongnu group, increased power and tried to unify Bing-Zhou Xiongnu groups. With such a movement, Si-Ma-Yan(司馬炎) unified the three nations and Argument of barbarian`s emigration(徙戎論) was strongly recommended to solve threat of immigrants, but Si-Ma-Yan(Wu-ti, 武帝) didn`t accept it. Si-Ma-Yan rather repressed the uprising of Liu-Bao, divided Bing-Zhou Xiongnu groups into five, and tried to separate the power by making Du-Wei(都尉), the Chinese official position for control. Besides, Si-Ma-Yan captured former Shanyu`s descendant, Liu-Yuan(劉淵), in Luo-Yang(洛陽) to prevent his stronger power. This was a realistic method of preventing the unity of Xiongnu while might strongly control them. However, such a countermeasure of the Royal Court was not successful as the reign of Xi-Jin(西晉) collapsed without time enough to change the power relationship inside the Xiongnu groups. On the other hand, Liu-Yuan took the chance and returned to Shan-Xi(山西) so it founded the new country in central districts on the basis of Xiongnu`s own tribe organization system. As a result, so-called Wu-Hu-Shi-Liu(五胡十六國) era has begun.