The Jin dynasty was founded by Sima Yan 司馬炎 (Emperor Wu 晉武帝, r. 265-289), who hailed from a family of powerful generals and was able to overthrow the house of Cao 曹 that had ruled over the empire of Wei 魏 (220-265), one of the Three Kingdoms 三國 (220-280).
Sima Yan took over the complete political and administrative system of the Wei empire, but also its structural weaknesses, particularly the inability of the central government to dominate the local aristocracy and to deprive of of their rights on levying taxes and maintaining their own armies.
During the Later Han period 後漢 (25-220 CE), the social stratum of eminent families (shijia 世家, dazu 大族, haozu 豪族, shizu 士族), possessing large tracts of lands, had also been allowed to participate in certain government affairs because of their education in the sense of socially and politically responsible Confucianism. Yet during the Wei and Jin periods members of the local gentry did only occasionally have access to high state offices. These were reserved for members of the imperial house. The decay of Confucian education and the Confucian-style central government led to an attitude of the aristocracy to remain on their estates and fortified manors (wubao 塢保) instead of engaging in political matters.
The family Sima had therefore a lower intellectual background than the Han rulers before, and were not as much supported by the local aristocracy than the imperial house of the Han had been. Furthermore, the tendency of independent peasants to escape the heavy burden of taxes and corvée labor by hiring out themselves as tenant farmers or even to sell themselves into slavery resulted in a very small financial base for the central government because only self-employed and independent farmers were taxed.
The area southeast of the lower Yangtze reaches (Jiangdong 江東) was nominally reigned by the Jin dynasty. The factual power instead remained by the local magnates and estate owners, former subjects of the empire of Wu 吳 (222-280). The ruling dynasty of the Wu empire had granted them generous freedom in political and fiscal questions, and the Sima emperors of the Jin dynasty followed this pattern in order to win the support of the southeasterrn gentry.
The paramount victory of Sima Yan during the power struggles among the aristocracy of the later Wei period had trapped Sima Yan in a consciousness that it was not necessary to appease the many influential gentry families of the north and of the newly conquered south. Instead of further disempowering other families, Sima Yan generously bestowed titles of nobility and princedoms (wangguo 王國) to members of his own family. These princes were even allowed to maintain their own armies. This situation crucially contributed to the disintegratiion of the Jin empire after Sima Yan's death.
The fifteen years of power struggles inside the imperial family Sima, by historians called the Rebellions of the Eight Princes (bawang zhi luan 八王之亂) or "disturbances of the Yongjia reign-period" (Yongjia zhi luan 永嘉之亂), indirectly led to the downfall of the Western Jin dynasty 西晉 (265-316).
Already during the lifetime of Emperor Wu the court officials disagreed about the question who should be the heir apparent. Sima Yan's younger brother Sima You 司馬攸 (248-283), Prince of Qi 齊, who was long favoured, died untimely. Emperor Wu was therefore succeeded by his son Sima Zhong 司馬衷 (Emperor Hui 晉惠帝, r. 289-306). Emperor Hui was supported in government by Yang Jun 楊駿, a relative of his mother (Empress Dowager Yang 楊太后), who acted as regent for the young ruler. Emperor Hui's wife Empress Jia 賈后 tried to shovel important government posts on to her own family, a pattern of behaviour that had already been in use during the Han period.
Im 291, Empress Jia allowed Sima Wei 司馬瑋, the Prince of Chu 楚, to enter the capital with his troops to extirpate the Yang family. The regency of the empire fell into the hands of Sima Liang 司馬亮, the Prince of Runan 汝南, and Wei Guan 衛瓘. On order of the Empress, Sima Wei killed the new regent, but he was soon himself eliminated by the Empress. The important governmental posts were filled now with members and supporters of the Jia family, like Jia Mo 賈模, Jia Mi 賈謐, and their supporters like Zhang Hua 張華, Pei Wei 裴頠, and Wang Rong 王戎. After the Empress had in 300 the Heir Apparent Sima Yu 司馬遹 killed, the other princes rose in rebellion.
Sima Tong 司馬彤, the Prince of Liang 梁, and Sima Lun 司馬倫, teh Prince of Zhao 趙, entered the capital Luoyang 洛陽 (today in Henan) and killed the Empress and her followers. Sima Lun took over the civil and military government and tried to make himself emperor in 301. Another group of princes under the leadership of Sima Jiong 司馬冏, Prince of Qi 齊, Sima Yin 司馬穎, Prince of Chengdu 成都, and Sima Yong 司馬顒, Prince of Hejian 河間, rehabilitated the defenseless Emperor Hui. Sima Jiong took over the crucial government functions. When the Heir Apparent Sima Shang 司馬尚 died in 302 without an issue, Sima Jiong installed the minor-age prince Sima Tan 司馬覃 as heir apparent. This action provoked a new rebellion, this time led by Sima Yong, Sima Xin 司馬歆, the Duke of Xinye 新野, and Sima Xiao 司馬虓, the Prince of Fanyang 范陽). Sima Yi 司馬乂, the Prince of Changsha 長沙, killed Sima Jiong and took over the government functions in Luoyang.
The year 303 brought a dramatical increase in belligerent acitivites. With an enormous army, Sima Ying and Sima Yong beleaguered the capital. Sima Yue 司馬越, the Prince of Donghai 東海, killed Sima Yi and took over the government, residing on his own estates instead of in the capital. In order to secure his grip on Luoyang, he garrisoned an army in the capital. The attempt of Sima Yue, Sima Chi 司馬熾, the Prince of Yuzhang 豫章, and Sima Fan 司馬范, the Prince of Xiangyang 襄陽, to overthrow Sima Yue, failed. The next attempt to topple him came from the side of Sima Teng 司馬騰, the Duke of Dongying 東瀛, and Wang Jun 王浚, regional inspector (cishi 刺史) of the province of Youzhou 幽州. They made use of armies staffed with non-Chinese Wuhuan 烏桓 and Xianbei 鮮卑 cavalry. Sima Ying thereupon kidnapped the helpless Emperor Hui and abducted him to the secondary capital Chang'an 長安 (modern Xi'an 西安, Shaanxi). Sima Chi took over the regency for the high-jacked emperor. Only in 306, Sima Yue was able to subdue Sima Ying and finally made an end to the power struggles. Emperor Hui was welcomed back to Luoyang, but he died in the same year.
During the twelve and more years of power struggle at the court of the Jin dynasty, the peasant population was afflicted by distress, calamities and hunger. Many peasants had left their fields or the field they had rented, and roamed around the country (peasant refugees, liumin 流民) in the search for food and labour. In the northwestern parts of the empire, numerous non-Chinese immigrants from the peoples of the Di 氐, Xianbei, Qiang 羌, and Xiongnu 匈奴 had settled among the Chinese population since several decades.
Since the 290es, numerous rebellions against the disintegrating central government of the Jin dynasty took place. Zhang Chang 張昌 occupied a vast territory in modern Hubei, Qiu Shen 丘沈 called himself Liu Ni 劉尼 and regarded himself as a descendant of the great Han dynasty. He controlled the whole area of the middle and lower Yangtze River. Similar popular rebellions was undertaken and lead by Wang Ru 王如, Pang Shi 龐實, Hou Tuo 侯脫, Li Xiang 李驤, and Du Tao 杜韜. In Sichuan, the Di chieftain Li Te 李特 and his descendants founded the Cheng-Han empire 成漢 (304-347), first of a group of "barbarian" kingdoms and empires that eventually controlled northern China for more than one century.
As early as the last decades of Later Han period and the following power vacuum in the northwest of China, numerous non-Chinese tribes penetrated into areas that had already been inhabited by Chinese settlers. During the Wei period non-Chinese tribes were even invited to settle within the Chineses borders to compensate the population "deficit" that had accrued during the previous warfare activities. People like the Xiongnu, Qiang, Di, Xianbei (Murong 慕容, Yuwen 宇文, Duan 段, Tuoba 拓拔, Qifu 乞伏, Tuyuhun 吐谷渾) and Wuhuan more and more became accustomed to Chinese language and culture.
In the first years of the Jin period many of these tribes were enlisted in the normal household registers (bianhu 編戶) and had to pay taxes and to deliver corvée labour. Sometimes discriminated, these foreign peoples started to become rebellious against their Chinese suppressors, like Tufa Shuji 禿髮樹機 (a Xianbei chieftain) in 270, Liu Meng 劉猛 (a Xiongnu leader) in 279, and She San 赦散 (a Xiongnu) in 294. The court of the Jin therefore developed plans to resettle these peoples in their original homelands.
During the Rebellion of the Eight Princes, many of the warlords hired non-Chinese soldiers – quite similar to the Romans, in whose armies consisted of more than 50 per cent of German mercenaries. The Xiongnu ruler Liu Yuan 劉淵 was bestowed with Chinese military titles before he made himself king of Han 漢 and finally emperor of Han in 308. One of his followers, the Qiang chieftain Shi Le 石勒, was employed as "conquerer of the east". Shi Le became one of the mightiest and most ruthless "barbarian" rulers and dynastic founders in the fourth century. For 130 years, China would be controlled by the so-called Sixteen Kingdoms of the Five Barbarian Peoples 五胡十六國 (300~430).
The increasing drive of conquest and the rebellions of the non-Chinese population in the north against the Jin dynasty and the local Chinese gentry led to an enourmous exodus of Chinese peasants, landowners, and aristocrats to the south, especially into the lower Yangtze area. Many peasants literally ran for their life. The fleeing landowners took with them their whole households that included slaves, servants, and tenant farmers working on their fields. The imperial household was evacuated relatively late, in 310, when the "barbarians" had already crossed the Yellow River and beleaguered the capital Luoyang.
Led by Sima Yue, Sima Fan 司馬范 and Wang Yan 王衍, the imperial household finally crossed the Yellow River, too, and took refuge in the former capital of the Wu empire, Jianye 建業 (modern Nanjing 南京, Jiangsu), that was renamed Jiankang 建康. The number of the surviving members of the imperial family was reduced seriously.
Emperor Huai 晉懷帝, r. 306-312), who had planned to escape to Chang'an, was killed by the Xiongnu leader Liu Yao 劉曜. Sima Rui 司馬睿, the Prince of Langya 琅琊, who resided in the southeast, quickly enthroned Sima Ye 司馬鄴, the Prince of Qin 秦 (known as Emperor Min 晉愍帝, r. 313-316) as the new ruler of the Jin, but the emperor was soon captured by Liu Yao was killed in 317.
Sima Rui decided to adopt the title of Prince of Jin, and a year later took over the throne. He ruled as Emperor Yuan 晉元帝 (r. 317-322) from the southeast, while north China and the Sichuan Basin were lost to foreign warlords, many of which founded their own dynasties.
Following to the examples of the Eastern Zhou 東周 (770-221 BCE) and Eastern Han 東漢 (25-220 CE) dynasties that both had started in the west and ended in the east, the unbroken rulership of the Jin dynasty was euphemistically called "Eastern Jin" 東晉 (317-420).
Together with the surviving ministers of the central government and the imperial family numerous landowning families of the aristocracy (tuzu 土族) from northern China had fled to the more secure area of the River Huai 淮 and to the Yangtze delta. Most of them carried their family registers (jiapu 家譜) with them to testify later – in the case they could return to the north – that they had been owners of large estates. In the first decades after the exodus and escape to the south, the household registers of the northern immigrants were seen as provisional and were therefore written on paper that was not treated with the yellow conservant chemical – hence the difference between the yellow household registers (huangji 黃籍) of the native southeners and the white household registers (baiji 白籍) of the northern immigrants.
Together with the imperial family most of the high officials at the court of Jianye like Zhou Ji 周玘, Wang Dao 王導 or Diao Xie 刁協, were members of the northern aristocracy and the northern magnates. Southeners suddenly saw themselves ruled and dominatedby foreign families that had come from the north. Scores of local uprisings against the new domination by the "foreign" Jin aristocracy occurred during the first half of the fourth century.
A very important aim not only of the ruling class, but also among the refugees and the intellectuals was to conquer back the north of China. Some of the military campaigns could indeed gain back important territories, like the campaign of Zu Ti 祖逖 in 310 who conquered the River Huai region, the destruction of the Cheng-Han empire in 346, or the conquest of a great part of modern Shandong by general Liu Yu 劉裕. After the victorious battle of Feishui 淝水 (often falsely written 肥水; between modern Hefei 合肥 and Huainan 淮南, Anhui) in 383, the frontier between the Eastern Jin territory and the Former Qin 前秦 (351-394) empire in the north became a stable border for a long time.
The political history of Eastern Jin is characterized by changing constellation of powerful families and their supporters. These families all belonged to the immigrated northern aristocracy. The first phase is dominated by the family Wang 王 from the old Langya 琅琊 (with the main representants Wang Dao 王導 and Wang Dun 王敦), the second phase by the Yu family 庾 from Yingchuan 穎川 (Yu Liang 庾亮), the third phase by the Huan 桓 family from Qiao 譙 (Huan Wen 桓溫), and finally the fourth phase by the Xie 謝 family from Chen 陳 (Xie Shang 謝尚, Xie An 謝安 and Xie Xuan 謝玄).
Some of these potentates were real challengers of the imperial throne. Wang Dun for example tried to make himself emperor in 323, and Huan Wen dethroned Sima Yi 司馬奕 (Duke of Haixi 海西, r. 365-370) in 371 and made Sima Yu 司馬昱 ruler (Emperor Jianwen 晉簡文帝, r. 371-372). Huan Wen's power was ended by the new emperor who did not want to install Huan Wen as regent but nominated Sima Yao 司馬耀 his successor (Emperor Xiaowu 晉孝武帝, r. 372-396).
Apart from the mighty families, some rebellions and insurgencies endangered the imperial power like the uprising of Su Jun 蘇峻, who occupied and devastated the capital in 328.
Although Sima Daozi 司馬道子 and Sima Yuanxian 司馬元顯 were able to assure the central position of the imperial power of their family, the last years of the Eastern Jin dynasty are marked by constant power struggles between the imperial house and the occupants of high government posts. Chancellors, regional inspectors, generals and ministers like Wang Guobao 王國寶, Wang Gong 王恭, and Yin Zhongkan 殷仲堪 fought for influence and power and forged coalitions with princes of the imperial family.
During these years, the decisive rebellion was the religious-led movements of Sun En 孫恩 and Lu Xun 盧循 in 399 and 412. Sun En was head of a Daoist rebellion whose ideas originated in the sect of the Five-Pecks-of-Grain (Wudoumi dao 五斗米道). Many of the local magnates who felt suppressed by the northern immigrant regime sympathized with the rebellion. Although Sun En and later Lu Xun were not able to conquer the capital, there was an opportunity for Huan Xuan 桓玄 to occupy Jiankang and to make himself emperor of Chu 楚.
General Liu Yu, who was famous for his successful campaigns against the northern barbarian empires, overthrew Huan Xuan and enthroned Sima Dezong 司馬德宗 (Emperor An 晉安帝, r. 396-418). He was rewarded with the title of Prince of Song 宋, yet Liu Yu then killed Emperor Dezong and enthroned his brother Sima Dewen 司馬德文 (Emperor Gong 晉恭帝, r. 419-420).