Western Jin was the first dynasty to be overthrown by a Chinese minority ethnic group, the Huns. Before it was overthrown, Western Jin grew for 52 years, under the rule of four emperors.
During the Three Kingdoms Period (220 AD – 280 AD), Sima Yi Had assisted Wei State as it overthrew the Shu State, later overthrowing Wei as well. After his death, Sima Yi's sons Sima Shi and Sima Zhao consecutively controlled State Wei. Sima Zhao's power was so great that he proclaimed himself King Jin and named his son, Sima Yan, crown prince. In 265 AD, Sima Zhao died and Sima Yan dethroned the emperor of State Wei, Cao Huan, and then changed the state's name to 'Jin', making Luoyang (Henan Province today) the capital city. Sima Yan then became Emperor Jinwu, the first emperor of Western Jin.
After ascending the throne, Sima Yan overturned what remained of the Wu State, unifying China. He then crowned many members of the royal family in order to establish a powerful government (he attributed the downfall of the State of Wei to weaknesses in the royal clan's power). This, however, did not work out as planned - soon many of the beneficiary kings began to extend their spheres of influence, resulting in the 'Rebellion of the Eight Kings'. This rebellion was initiated by eight kings of the Western Jin Dynasty who sought to contend the domination of Western Jin. The rebellion lasted 16 years, from 291 AD to 306 AD.
Upon Emperor Jinwu's Death, his second son, Emperor Jinhui, Sima Zhong, took the throne. Sima Zhong was a fool and unable to govern the country, so most of the power was controlled by Empress Jia. The Rebellion of the Eight Kings took place during his reign. The rebellion wrought serious damages on the people and cities – especially Luoyang (Henan Province today) and Changan (Xian today). The Huns, Di, Serbi and other immigrant ethnic groups seized the opportunity and rebelled against Western Jin, causing its downfall as well. The emperors who followed Sima Zhong's rule (Emperor Huai - Sima Chi and Emperor Min) were puppet leaders.
In 308 AD, Liu Yuan, leader of the Huns, proclaimed himself king and set out to destroy the Jin Dynasty. In 316 AD, Changan was captured and Emperor Min – Sima surrendered, signaling the end of the Western Jin Dynasty.
Once he had unified the country, Sima Yan took significant steps to develop agriculture and appease the general population. He encouraged production, reduced the rate of unpaid labor, worked to decrease homelessness, and embarked on numerous water conservation projects. Unfortunately, the socioeconomic progress that resulted from Emperor Jinwu's reign fell apart after his death.
The disorder that sprung from Emperor Jinwu's death did, though, inspire numerous works of cultural and literary significance, including Maijing (Manual of the Pulses) by Wang Shuhe and the History of the Three Kingdoms (Sanguo Zhi) by Chen Shou.