War of the Eight Princes
While initial conflicts were relatively minor and confined to the imperial capital of Luoyang and its surroundings, the scope of the war expanded with each new prince who entered the struggle.
The initial period (290–291) mainly concerns the power struggle between the Yang and Jia clans as they fought for control for Emperor Hui in the wake of his ascension.
The later period (300–306) began following the fall of the Jia clan, who held power over the imperial court behind Emperor Hui for a decade before they were deposed by Sima Lun in 300.
This period, particularly after Sima Lun's usurpation in February 301, escalated into a series of civil wars in northern China as Emperor Hui changed hands several times to the remaining six princes.
By empowering the princes, Emperor Wu intended for them to act as a safeguard for his successors against the gentry clans should they overstep their boundaries, even more so considering Sima Zhong's disability.
The War of the Eight Princes coincided with the upheaval of the so-called "Five Barbarians"; non-Chinese groups that had been resettling into the Chinese interior as far back as the Eastern Han dynasty.
Through their civil wars and mismanagement of the empire, the Jin lost support from both the Chinese peasantry and the non-Chinese tribes, pushing them to join rebel groups in different parts of China.
As the emperor's health declined, Yang Jun sought to monopolize his control over Zhong as consort kin, first by sending away Sima Liang to Xuchang and then by forcing his court rival, Wei Guan, into retirement.
On the night of 23 April 291, Empress Jia and her allies sent out an imperial edict calling for the deposal of Yang Jun and occupied the gates leading to his residence.
They attempted to strip him of his military power and send him back to his fief in Jing province, but Wei retaliated by conspiring with Empress Jia to depose them, claiming to her that the two were planning to overthrow her.
Despite the efforts of ministers like Zhang Hua and Pei Wei to uphold the government's functionality, the imperial court under the Jia clan was beset with widespread corruption and bribery.
The rebellion in Qin and Yong coincided with famines and plagues, and although it was ultimately put down in 299, it sparked an influx of refugees fleeing south to Yi province.
They awarded their family members and allies with high-ranking positions and noble titles, while also posthumously honoring Sima Yu and recruiting famed individuals into their administration to win the people's support.
Meanwhile, the Prince of Qi, Sima Jiong, who played a vital part in Empress Jia's arrest, was unhappy with the positions he received under Lun's administration.
The following year, he claimed in a report that the spirit of his father, Sima Yi, had ordered him to move into the Western Palace (西宮), the residence of Emperor Hui.
Lun recalled a segment of his army to defend Luoyang, but when news of Zhang Hong's recent victories reached him, he sent them out again to attack Sima Ying.
Sun Hui led the main army against Ying at Huangqiao (黃橋, in present-day Wen County, Henan), defeating the prince's vanguard and killing 10,000.
As the coalition forces approached, officials and generals in the capital began to turn on Lun and Sun Xiu despite their attempts to suppress reports of their losses.
In a letter to Jiong, Wang Bao urged him to send the princes back to their respective fiefs and to divide control over the state between him and Sima Ying.
At the time, Sima Ying was setting out to quell Zhang Chang's rebellion, but hearing about the situation in Luoyang and Guanzhong, he took his troops to join Yong instead, once again ignoring Lu Zhi's advice.
Meanwhile, Emperor Hui was constantly on the move and shifting his base before he defeated Ying's troops at Goushi (緱氏; in present-day Yanshi District, Henan) on 22 October.
[21] Although Ai was defeated, Yong was still threatened by Liu Chen, while Huangfu Zhong continued to resist in his city of Jicheng (冀城; in present-day Gangu County, Gansu).
With Yue defeated, Ying then planned to eliminate the Chief Controller of You province, Wang Jun, a former partisan of Empress Jia who refused to join the coalition against Sima Lun.
His forces swelled to over 50,000 and would continue to grow as both the Chinese peasants and non-Chinese tribes joined them in their resentment towards the Jin in light of the civil wars and famines.
Although Emperor Hui was now in Chang’an, the influential ministers, Xun Fan, Liu Tun, and Zhou Fu, were left behind in Luoyang to run a separate court.
His brothers and several other prominent governors such as Wang Jun and Sima Xiao all joined him, and he also began handing out new appointments to his allies without the emperor's assent.
Yet, Yue was also wary of the new emperor's capabilities and was likely insecure about his own position due to the various coups and civil wars that led to the downfalls of his predecessors in recent years.
Ji Sang and Shi Le sacked Ye in 307, killing Sima Teng in the process, while Wang Mi wreaked havoc on the North China Plain, going as far as occupying Xuchang and laying siege on Luoyang in 308.
Although Yue eventually quelled their rebellions, both Shi Le and Wang Mi brought their remaining forces to join Liu Yuan's state of Han.
Five years after his death, both the capitals of Chang'an and Luoyang had been lost and most of northern China fell under the rule of an assortment of short-lived states known as the Sixteen Kingdoms.
