<P> After Dong Zhuo withdrew to Chang'an, he maintained an even tighter grip on the government and cruelly dealt with all dissent against him . Interior Minister Wang Yun and a few other officials, including Huang Wan (黃 琬), Shisun Rui (士 孫 瑞), and Yang Zan (楊 瓚), plotted to eliminate Dong Zhuo . They eventually persuaded Dong Zhuo's foster son, Lü Bu, to join them . Lü Bu bore a grudge against Dong Zhuo because the latter almost killed him once during a fit of anger, and also because he was afraid that his secret affair with one of Dong Zhuo's maids might be exposed . In May 192, the conspirators, led by Lü Bu and Wang Yun, assassinated Dong Zhuo and slaughtered his clan . </P> <P> After Dong Zhuo's death, it was believed that the chaos caused by Dong Zhuo's "reign of terror" would subside, and the central government would be restored to its original state . However, although Wang Yun was regarded as a capable minister, he gradually became arrogant and made several key mistakes that would cause his downfall . He failed to maintain good relations with Lü Bu, and strongly refused to grant amnesty to the surviving followers of Dong Zhuo and ordered them to be disbanded . This caused Dong Zhuo's men to fear that they might be massacred . Dong Zhuo's son - in - law, Niu Fu, took control of Dong's forces in Liang Province and resisted Wang Yun, but later died in a friendly fire incident . Niu Fu's subordinates, Li Jue, Guo Si and Fan Chou, wanted to submit to the imperial court, but as they had previously resisted Wang Yun, Wang now rejected their request for amnesty . Li Jue, Guo Si and Fan Chou led their armies to attack Chang'an and took control of the government . Wang Yun was captured and executed along with his family, while Lü Bu was defeated and driven away . </P> <P> After taking control over the imperial court in Chang'an, Li Jue, Guo Si and Fan Chou did as they pleased without showing any regard for the welfare of the state . Concurrently, provincial warlords all over China battled each other to expand their territories or further their personal interests . Some of those warlords were friendly with Li Jue's forces, while others remained hostile to them, even though all of them nominally acknowledged Emperor Xian as the sovereign ruler of China . </P> <P> In 193, armed conflict broke out between the northern warlords Liu Yu and Gongsun Zan . Liu Yu strongly opposed warfare while Gongsun Zan continuously waged war against Yuan Shao . Liu Yu and Gongsun Zan made accusations against each other in their respective memorials to Emperor Xian . Eventually, Liu Yu was unable to tolerate Gongsun Zan and attacked the latter, but was defeated and killed . </P>

What led to the collapse of the han dynasty