Jin Dynasty
A era of relative prosperity had existed since Jin Wudi unified China in 280. Wu hu tribes residing inside and near China regularly paid taxes to the Jin court. They traded horses and animal products for agricultural goods and silk. Mercenaries could always be called upon. The scenario resembled that of Eastern Han Dynasty with one exception: the internal weakness of the dynasty provided the Wu Hu with the chance to become rulers of China.
An important reason for this weakness was the influence of the principal landholding families. These families were so powerful that the founders of the Three Kingdoms had to rely on them to establish their domains. The Nine grade controller system, by which prominent individuals in each administrative area were given the authority to rank local families and individuals in nine grades according to their potential for government service, further consolidated their authority. Because the ranking was arbitrarily decided by a few prominent persons, it frequently reflected the wishes of the leading families in the area rather than the merit of those being ranked.
Since individuals from the elites were almost guaranteed bureaucratic posts without ever working hard, many found other ways of killing time. They engaged either in extravagantly showing off their wealth or time-consuming and often useless discussions on Daoism. Such pastimes were so popular that the minority of hard working individuals were often despised. Local officials and nobles often exploited both peasants and Wu Hu herdsmen for personal gain and in order to bribe officials for higher posts.
Although the Jin Dynasty was slowly deteriorating socially and politically, some officials did foresee the crisis. Discussion of the God of Money (錢神論 Qián Shén Lùn) and Discussion on Tribe Relocation (徒戎論 Tú Róng Lùn) acutely reflected the extravagant livelihood and the possibility of an uprising of the Wu Hu. The latter work provides accurate locations of the region where the Wu Hu resided. Southern Xiongnu now dominated Bingzhou (in modern Shanxi province) and their horsemen could arrive at Jinyang (Taiyuan) in half-a-day's ride and Luoyang, the capital, in a few days.
Read more about this topic: Wu Hu