Upheaval of the Five Barbarians

When the Jin dynasty was established in 266, Emperor Wu of Jin sought to learn from the mistakes of his predecessor, the Cao Wei, by empowering the princes. Unlike during the Wei period, the princes were allowed to become military governors and were given personal armies in their fiefdoms. After unifying China in 280, Emperor Wu issued for the demobilization of every province and commandery in the empire and reduced the military authority of the provincial inspector into a civilian role. Only 100 military officials were stationed in large commanderies, while smaller commanderies only had 50.

The emperor had hope that by concentrating military power in the hands of the princes, it would help deter usurpers from the gentry clans. However, the ensuing War of the Eight Princes after his death in 290 undid any potential good from his policies. His successor, Emperor Hui of Jin, was developmentally disabled, making him a mere figurehead to be taken advantage of. Rather than protecting him, the princes pitted their soldiers against one another in a conflict for control over the imperial court.

While the Jin military weakened itself under the princes, many defenseless commanderies became targets for rebellion by the empire's disgruntled or opportunistic subjects. In the finals years of the Western Jin, nomadic subjects collectively known as the Five Barbarians emerged dominant over northern and western China. These Five Barbarians were the Xiongnu, Jie, Qiang, Di and Xianbei.

The migration of the nomadic people into the Chinese interior had been ongoing since the Han dynasty. In 50 CE, a few years after the Xiongnu empire was divided into north and south, the Southern Xiongnu became a vassal of the Han. They moved their court to Xihe Commandery in Bing province and resettled in the frontier commanderies within the Great Wall. They were dependent on trade with the Han and cooperated with them to destroy the rival Northern Xiongnu. Although relations between the two sides declined in the later years with the Xiongnu occasionally rebelling, the Xiongnu remained a vassal to the Han dynasty up to its end in 220 to the Cao Wei.[9]

In 216, the warlord, Cao Cao, abolished the chanyu position and divided the Southern Xiongnu into five divisions around Taiyuan Commandery, away from the frontier in hopes to deter them from rebelling. Gradually throughout the Cao Wei and early Western Jin periods, the Xiongnu elites began expressing resentment towards their new way of life. During the Jiaping era (249–254), the five divisions were unified as one under Liu Bao, but was gradually forced by the Wei-Jin imperial courts to split back to five. In 272, one of the Xiongnu leaders, Liu Meng rebelled against Jin in Bing but was defeated in a matter of months. In 294, another leader, Hao San (郝散), rebelled in Shangdang Commandery, but was also quickly dispatched. As the Xiongnu noble, Liu Xuan, states in the Book of Jin:

“In the past, our ancestors and those of the Han acted like brothers through joy and sorrow. However, since the fall of Han and the rise of Wei and Jin, our titles of chanyus hold no value, and we have not gained a foot of land since. Although we have been bestowed with many noble ranks, our households are all equally low."

Another ethnic group living in Bing at the time were the Jie people. Their exact origins is still debated by scholars today, but it is believed that they were once a part of the Southern Xiongnu and later resided in Shangdang. In 303, Bing was struck by famine, which displaced many of the Xiongnu, Jie and other tribal populace. The provincial inspector, Sima Teng, had these people captured and sold into slavery to fund his army for an ongoing civil war.

After the Han established their presence in the Hexi Corridor in 121 BC, the Qiang people of the Tibetan Plateau became a recurring threat to them in northwestern China. To appease them, the Qiang were sometimes allowed to resettle into the Guanzhong area, as well as the watersheds of the Wei and Jing rivers. There, they lived together with Han immigrants but faced oppression from the local administrators, which frequently led to rebellions. Living close to the Qiang were the Di people, who dispersed throughout the Central Plains after the Han defeated them to establish Wudu Commandery in 108 BC.

The fall of Han and the Three Kingdoms period further encouraged the immigration of nomadic people to repopulate devastated areas and provide military power and labour. The Guanzhong region in particular became a contested region between warlords and later between the states of Cao Wei and Shu Han. In 219, Cao Cao relocated around 50,000 Di from Wudu to Tianshui and Fufeng commanderies. The Qiang and Di people were numerous in northwestern China, and they often fought for Wei and Shu depending on their circumstances. Other nomadic people who lived or resettled in the northwest included the Lushui barbarians (盧水胡) and Xianbei tribes such as the Tufa (禿髮).

While the situtation was relatively controlled under Wei, the northwest descended into chaos under Western Jin as they lost the support of the tribes due to inept governance. In 270, the Xianbei chieftain, Tufa Shujineng, led a multi-ethnic rebellion against Jin in Liang and Qin provinces that lasted until 279, with the rebels even briefly taking control over Liang. From 296 to 299, the various tribes rebelled again, this time within Guanzhong and acclaiming the Di chieftain, Qi Wannian as their emperor. These rebellions were accompanied by famines and plagues, with Qi Wannian's rebellion being so severe that it devastated Guanzhong and prompted tens of thousands of refugees to move into Hanzhong and Sichuan in search of food.[10]

Following the fragmentation of the Xianbei confederation, the Murong, Duan and Yuwen tribes moved to the Liaoxi region where the three developed a rivalry with one another. The Murong was the first to affiliate themselves with the Central Plains dynasties starting with the Cao Wei in 238. They remained affiliated even after the founding of Jin, and despite a war between both sides from 281 to 289, the Murong resubmitted to Jin and their chieftain, Murong Hui, was appointed Commander of the Xianbei. Meanwhile, in 258, another Xianbei tribe, the Tuoba, occupied the abandon city of Shengle and also became a vassal of Wei and Jin.

At the turn of the 4th century, the Inspector of You province, Wang Jun, sought to consolidate his control over his province amidst the War of the Eight Princes. He allied himself with the neighbouring Duan tribe and a chief of the Yuwen as well as other smaller tribes like from the Wuhuan. The Xianbei provided him with troops who fought in the campaigns against Sima Ying and Sima Yong, playing a crucial role in securing Sima Yue's victory in the civil war. However, they also partook in the sacking of Ye in 304 and Chang'an in 306, killing thousands of the cities' inhabitants.

The Xianbei's effectiveness saw them continued use after the civil war by northern governors to contain the growing threat of Han-Zhao, eventually enlisting the help of the Tuoba tribe as well. However, it also created an overdependence that would cost Jin dearly in the later stages of the war.

In 304, the Xiongnu nobility in Bing province conspired to take advantage of the Jin princes' infighting to break away from the empire. Serving under the prince, Sima Ying, was the Xiongnu general, Liu Yuan. Liu Yuan was the grandson of the Southern Xiongnu chanyu, Yufuluo, although some modern Chinese historians doubt this claim, instead believing he was a member of the non-related but influential Tuge tribe (屠各部). He was a Sinicized Xiongnu, having spent his youth in the Chinese capital Luoyang as a hostage and being educated with Chinese-Confucian literature. After leaving Luoyang, Liu Yuan served a series of offices under Jin to oversee the Xiongnu tribes in Bing, during which he won the support of both the Xiongnu and Han people in Bing, You and Ji provinces.

Under Sima Ying, Liu Yuan served as the Chief Controller of the Five Divisions in the prince's base, Ye. Liu Yuan's granduncle, Liu Xuan, convinced the conspirators to elect Liu Yuan as their leader, so they sent an envoy to inform him of the plot and offered him the title of Grand Chanyu. At the time, Sima Ying was on the verge of defeat as Wang Jun's forces marched onto Ye. After agreeing to join the plot, Liu Yuan convinced Sima Ying to allow him to return to Bing so that he could gather the Xiongnu tribes to help fight Wang Jun. Once Liu Yuan reached Lishi, he was installed as the new Grand Chanyu and rallied around 50,000 soldiers.[11]

Later in 304, Liu Yuan established the state of Han (renamed Zhao in 319, thus the name Han-Zhao). Despite being a Xiongnu, Liu Yuan depicted his state as a continuation of the Han dynasty, citing that his ancestor, Modu Chanyu, was married to a Han princess through Heqin. He initially took the imperial title of King, only becoming Emperor in 308 to imitate the ascension of Emperor Gaozu of Han. He also honored the emperors of the Western, Eastern and Shu Han. To bolster his forces, he was willing to accept the Han Chinese and non-Xiongnu tribes to serve under him.[12][13][14][15][16][17][18][19][20]

Soon after becoming king, Liu Yuan greatly defeated a Jin force sent to quell his rebellion at Daling County (大陵縣; northeast of present-day Wenshui County, Shanxi). He then expanded his domain by capturing counties in Taiyuan and Xihe commaderies before suffering his first major defeat in 305. This defeat saw the first involvement of the Tuoba-Xianbei tribe in the war, as they provided Jin with their light cavalries to fight Han-Zhao. Along with a famine that forced him to move his capital to Lishi (離石; in modern Lüliang, Shanxi), Liu Yuan's expansion was temporarily stifled.

In the next few years, more rebellions began to break out in northeastern China. In 305, the general, Gongshi Fan rebelled in Hebei and in 306, the prefect, Liu Bogen (劉柏根), rebelled in Shandong. The two rebellions were swiftly dealt with by late-306, but Jin was unable to completely wipe out their forces, allowing their remnants to develop into more serious threats. Many of these rebel leaders were Han Chinese, but the most influential of them would prove to be Shi Le, a Jie chief who was previously sold into slavery during the famine in Bing province of 303 and 304.

After Gongshi Fan's defeat, his subordinates, Ji Sang and Shi Le, fled to the pastures of Shandong where they gathered followers, many of who were horse shepherds, and raided the surrounding counties. Their forces grew to such a size that in 307, they sacked the city of Ye and left it to burn for ten days. Around 10,000 people were killed including the city's commander, Sima Teng. However, after they left to invade Yan province, they suffered a string of defeats to the general, Gou Xi. Following a decisive defeat, the two decided to escape to Bing province to join Han-Zhao, but along the way, they were intercepted by Jin forces and forced to split up. Shi Le continued on to Bing while Ji Sang fled back to Shandong, where he was killed by refugees forces loyal to Sima Teng, the Qihuo.

Liu Bogen's subordinate, Wang Mi, also survived his superior's defeat and fled to Shandong, where he formed a bandit group. Much like Ji Sang and Shi Le, his forces grew immensely, and in 307, he invaded Qing and Xu provinces, ravaging the commanderies and killing many of the local officials. Wang Mi then attached himself to Han-Zhao, and in 308, his rebellion spilled over to Yan and Yu provinces while his forces swelled to the tens of thousands. He was even able to enter Xuchang and empty the city's arsenal before laying siege on Luoyang. However, the siege ended in failure as he was unable to break through the capital's defense. With his momentum coming to a halt, Wang Mi brought his forces over to Han-Zhao territory.

Under Liu Yuan, Shi Le and Wang Mi were elevated to powerful commanders. Wang Mi had previously befriended Liu Yuan during his youth in Luoyang and was thus immediately entrusted with important military affairs. Meanwhile, Shi Le, around the time of joining Han-Zhao, helped convinced the tribes of Shangdang Commandery and the Wuhuan people of Leping County (樂平; in present-day Jinzhong, Shanxi) into joining the state. For his deeds, he was given full command over the armies east of the Taihang Mountains.[21]

The chaos and devastation of the north led to a mass migration of Han Chinese to the areas south of the Huai River, where conditions were relatively stable. The southward migration of the Jin nobility is referred to in Chinese as yī guān nán dù (衣冠南渡, lit. "garments and headdresses moving south"). Many of those who fled south were of prominent families, who had the means to escape; among these prominent northern families were the Xie clan and the Wang clan, whose prominent members included Xie An and Wang Dao. Wang Dao, in particular, was instrumental in supporting Sima Rui to proclaim the Eastern Jin dynasty at Jiankang and serving as his chancellor. The Eastern Jin, dependent on established southern nobility as well as exiled northern nobility for its survival, became a relatively weak dynasty dominated by regional nobles who served as governors; nonetheless it would survive for another century as a southern regime.

The "Eight Great Surnames" were eight noble families who migrated from northern China to Fujian in southern China due to the uprising of the five barbarians when the Eastern Jin was founded, the Hu, He, Qiu, Dan, Zheng, Huang, Chen and Lin surnames.[27][28][29][30][31][32][33]

The different waves of migration such as the fourth century and Tang dynasty northern Han Chinese migrants to the south are claimed as the origin of various Chen families in Fuzhou, Fujian.[34] Mass migrations led to southern China's population growth, economic, agricultural and cultural development as it stayed peaceful unlike the north.[35][36][37][38][39][40][41] Yellow registers were used to record the original southern Han Chinese population before the migration and white registers were used to record the massive influx of commoner and aristocratic northern Han Chinese migrants by the Eastern Jin dynasty government.[42]

After the establishment of the Northern Wei in northern China and a return to stability, a small reverse migration of southern defectors to northern China took place. In Luoyang a Wu quarter was set up for southerners moving north.[43][44][45][46][47] Han Chinese male nobles and royals of the southern dynasties who fled north to defect married over half of Northern Wei Xianbei Tuoba princesses.[48] Southern Chinese from the southern capital of Jiankang (Nanjing) were deported to the northern capital of Chang'an by the Sui dynasty after reuniting China.[49]

Han Chinese refugees from the five barbarian uprising also migrated into the Korean peninsula[50] and into the Murong Former Yan state.[51][52][53][54] Eastern Jin maintained nominal suzerainty over the Murong state until 353 as the Murong accepted titles from them.[55] An official in the Murong state, Dong Shou defected to Goguryeo.[56][57][58][59][60][61] Han Chinese refugees migrated west into Han Chinese controlled Former Liang.[62][63][64]

The descendants of northern Han Chinese aristocrats who fled the five barbarians uprising to move south with the Eastern Jin and the local southern Han Chinese aristocrats already in southern China combined to form the Chinese Southern aristocracy in the Tang dynasty, in competition with the northeastern aristocracy and the mixed Han-Xianbei northwestern aristocracy of the former Northern Zhou who founded the Sui dynasty and Tang dynasty.[65][66] The southern aristocracy only intermarried with each other and viewed themselves as preserving Han culture.[67][68]

Southern Chinese Daoism developed as a result of a merger of the religious beliefs of the local southern Han Chinese aristocrats and northern Han Chinese emigres fleeing the five barbarians.[69] The Han aristocrats of both south and north were highly insular and closed against outsiders and descended from the same families who originally hailed from northern China.[70][71]