The rebellion of the eight princes (ba wang zhi luan 八王之亂) was a large-scale uprising of members of the imperial house against the central government of the Western Jin dynasty 西晉 (265-316). The rebellion continued for 16 years and initiated the downfall of the Western Jin by critically weakening its military performance.
|Sima Wei 司馬瑋 (271-291), Prince of Chu 楚|
|Sima Liang 司馬亮 (d. 291), Prince of Runan 汝南|
|Sima Lun 司馬倫 (249-301), Prince of Zhao 趙|
|Sima Jiong 司馬冏 (d. 302), Prince of Qi 齊|
|Sima Ying 司馬穎 (279-306), Prince of Chengdu 成都|
|Sima Yong 司馬顒 (d. 306), Prince of Hejian 河間|
|Sima Yi 司馬乂 (277-304), Prince of Changsha 長沙|
|Sima Yue 司馬越 (d. 311), Prince of Donghai 東海|
The existance of princedoms in the Jin empire goes back to the decision of Sima Yan 司馬炎, Emperor Wu 晉武帝 (r. 265-289 CE), to establish militarily strong local governments in order to built up a defense shield for the capital Luoyang 洛陽 (today in Henan). He was convinved that these local governments were to be entrusted into the hands of members of the imperial family, a constellation that would prevent any general from turning against the emperor. In 265 therefore, he gave 27 persons of his family the title of prince, which was endowed with a territory (princedom or kingdom, wangguo 王國). These could be freely dispose of their lands and had at hand strong military contingents of a maximum of 5,000 troops per kingdoms. Other members of the imperial family were appointed to high posts in the central and local governments, as well as with the command of important garrisons. Some of the princes also held the command of provincial troops. Prince Wei of Chu, for instance, was concurrent commander-in-chief (dudu 都督) of Jingzhou 荊州, and Prince Liang of Runan commanded the garrison of Xuchang 許昌. When Emperor Hui 晉惠帝 (r. 290-306) succeeded to the throne, he entrusted Sima Tong 司馬彤, Prince of Liang 梁, Prince Lun of Zhao and Prince Yong of Hejian with the defense of the metropolitan region and Prince Ying of Chengdu with the defense of the secondary capital Ye 鄴 (close to modern Anyang 安陽, Henan).
Shortly before Emperor Wu died, he entrusted his father-in-law Yang Jun 楊駿 (d. 291) with the regency for his successor. Yang Jun had been General of Chariots and Cavalry (cheji jiangjun 車騎將軍) was was now appointed Grand Mentor (taifu 太傅, see Three Dukes) and area commander-in-chief (da dudu 大都督). When Emperor Hui mounted the throne, his wife, Empress Jia Nanfeng 賈南風, conspired with Prince Wei of Chu and had the palace guard assassinated Yang Jun, so that the most powerful position could now be laid into the hands of Prince Liang of Runan and Grand Councilor (yuanlao 元老) Wei Guan 衛瓘 (220-291). This situation was not yet sufficient for Empress Jia, so that she instigated Prince Wei of Chu to kill Prince Liang. She thereupon charged Prince Wei guilty of high treason and thereupon took over personally the regency for the young Emperor Hui. Having reached the most powerful position in the empire, Empress Jia killed the heir apparent Sima Yu 司馬遹 (278-300). This incident caused Prince Lun of Zhao, who commanded the imperial guard, to conspire with Prince Jiong of Qi, to raise weapons and to kill the Empress. In 301 Prince Lun dethroned Emperor Hui and proclaimed himself emperor. This usurpation was the incending spark of the rebellion of the imperial princes.
Prince Jiong of Qi, commander of the garrison of Xuchang, was the first to raise weapons, and he was soon followed by Prince Ying of Chengdu, the commander of Ye, and Prince Yong of Hejian, the commander of the metropolitan region around Chang'an 長安 (modern Xi'an 西安, Shaanxi). Wang Yu, a high officer of the capital guard, killed the usurper and reenthroned Emperor Hui. Prince Jiong entered the capital with his troops under the pretext of protecting the Emperor as a regent for him. Prince Yong was not content with this new situation and approached the capital Luoyang with his troops in early 302. Prince Yi of Changsha, who at that time resided in the capital, likewise raised weapons against Prince Jiong and killed him, taking over regency by himself.
In 303 the princes Yong of Hejian and Ying of Chengdu decided to kill the new regent Prince Yi. Commander-in-chief Zhang Fang 張方 (d. 306) was ordered to march against the capital with his elite troops, while Prince Yong himself took with him an army of more than 20,000 troops. Although the regent's contingents were smaller, he several times defeated the rebellious princes Yong and Ying. Yet the rebels finally were able to encircle Luoyang and laid siege to the capital. Inside the walls, the defenders were unsure about to side with whom, and in early 304 Prince Yue of Donghai decided to arrest Prince Yi and to hand him over to Zhang Fang, who burnt his prisoner alive. Prince Ying of Chengdu, now the most powerful man of the empire, entered Luoyang, required the post of Counsellor-in-chief (chengxiang 丞相), yet he did not reside in the capital but instead returned to Ye, from where he, as the new regent, controled the politics of the empire.
Prince Yue of Donghai took the emperor as a hostage and attacked Prince Ying in Ye. He was defeated by Prince Ying in the battle of Dangyin 蕩陰 (modern Tangyin 湯陰, Henan), and Emperor Hui fell into the hands of the regent who took him prisoner in Ye. Prince Yue had fled to his territory in Donghai. Prince Yong had his right hand Zhang Fang secure the capital Luoyang, while he joined his forces with Prince Yue's brother Sima Teng 司馬騰, who was regional inspector (cishi 刺史) of the province of Bingzhou 幷州 (approx. modern Shanxi) and Wang Jun 王浚 (252-314), regional inspector of Youzhou 幽州 (around modern Beijing). They attacked Ye, so that the regent, Prince Ying, fled with his prisoner, the emperor, to Luoyang, and then to Chang'an in the west. In 305 Prince Yue had assembled new forces and attacked Prince Yong and defeated him. Only a year later he was able to liberate Emperor Hui and guided him back to the capital. The rebellious princes Ying and Yong were killed in subsequent battles, and the highest power in the empire fell into the hands of Prince Yue. The rebellion of the eight princes was ended.
The 16 years of interal trouble had cost a lot of lives, had led to the devastation of the large cities Luoyang and Chang'an, and had decreased the political role of the central government. Instead, the local governments and private landholders became more and more independant from the politial centre, arranging their own economic and social outcome. During that time of insecurity, several Non-Chinese tribes, especially Xiongnu 匈奴 and Xianbei 鮮卑, migrated into northern China. Some of them served as mercenaries for the princely armies. In the century to come, these tribes would drive out the Jin dynasty from northern China to the southeast (as Eastern Jin 東晉, 317-420) and found their own "barbarian" empires 五胡十六國 (300~430).