Ethnic tensions in the Guanzhong region between the Han and the tribes, primarily the Qiang and Di, led to major revolts which resulted in an exodus of refugees into southwestern China.

In the north, the Five Divisions of Bing province, descendants of the Southern Xiongnu, took advantage of the Jin prince's infighting to declare independence and establish the Han-Zhao in 304, acclaiming the noble, Liu Yuan as their leader.

As anti-Jin revolts spread to Hebei and Shandong, a former Jie slave, Shi Le, rose to prominence, and after joining Liu Yuan, he would effectively control the eastern part of his empire.

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.

Though the Xiongnu gradually ceased as a coherent ethnic group, Bing province remained home to various tribes who were vaguely referred to as hu and other terms for the non-Chinese.

Since the Western Han period, many of the Qiang submitted to the Chinese court and were allowed to settle in the Guanzhong region and the watersheds of the Wei and Jing rivers.

There, they practiced agriculture and lived together with Chinese settlers, but faced with oppression from the local administrators, they often instigated large-scale rebellions which adversely affected the Han military and economy.

Qi Wannian's rebellion was accompanied by famines and plagues so severe that it devastated the Guanzhong and prompted tens of thousands of refugees to move into Hanzhong and Sichuan in search of food.

In the northeast, where the Wuhuan people once dominated before their defeat at the Battle of White Wolf Mountain, the Xianbei Murong, Duan and Yuwen tribes came to fill in the power vacuum.

The Xianbei were a deciding factor in Sima Yue's victory in the civil war, but they also partook in the sacking of Ye in 304 and Chang'an in 306, killing thousands of the cities' inhabitants.

Modern historians and meteorologists believe that climate change was an important factor in the migration of nomadic peoples into the Chinese interior, as the weather became too cold and dry in the north for agriculture.

Chu Coching stated that there was a cold period from the Three Kingdoms to the Northern and Southern dynasties, with relevant historical records reporting cases of extreme weather phenomena, such as the freezings of the Huai River in 226 and the Bohai Sea in 336.

During the Taikang era (280–289), the Jin accepted a series of submissions from people claiming to be "Xiongnu" living outside the border, with the largest group coming in 286, purportedly at 100,000.

Li Te soon submitted back to Jin due to the arrival of the army led by the new inspector, Luo Shang but retained a significant amount of influence in the region as an acting representative for the refugee families.

Between 303 and 304, a Man official, Zhang Chang led a revolt that spread across Jing, Jiang, Xu, Yang and Yu provinces consisting of refugees and people evading the draft to fight against Li Te's rebellion.

After agreeing to join the plot, Liu Yuan received Sima Ying's permission to return to Bing so that he could gather the Five Divisions to help repel Wang Jun.

Official history states that Liu Yuan was a direct descendant of the Southern Xiongnu chanyu as the grandson of Yufuluo, although some modern Chinese historians have challenged this claim.

Many of these rebel leaders were Han Chinese, but the most influential of them would prove to be Shi Le, a Jie chieftain who was previously sold into slavery during the great famine in Bing province of 303.

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.

Claiming to avenge the popular Prince of Chengdu, Sima Ying who had recently died, their forces grew to such a size that in 307, they sacked the city of Ye and left it to burn for ten days.

[24][full citation needed] The defeat of Wang Yan's forces finally exhausted the military capacity of the Jin, leaving Luoyang open to capture.

Not long after recapturing Chang'an, these generals fought each other in a brief but bloody power struggle, with Emperor Min eventually falling into the hands of the pair, Suo Chen and Qu Yun.

After a disastrous campaign to attack Jiankang in 312, he took the advice of his advisor, Zhang Bin, to establish and cultivate a base in Xiangguo (襄國, in modern Xingtai, Hebei).

The two governors had trouble maintaining population in their territories, as initially, they would attract thousands of refugees, but just as many people would leave them to join the safer and better-managed Xianbei fiefdoms.

Other regimes that sprang up from the upheaval but are not considered as part of the Sixteen Kingdoms were the Di-led Chouchi, the Tuoba-led Dai, the Duan and Yuwen states in Liaoxi, and the Tiefu tribe around the Ordos Plateau.

Following Emperor Min's death, Sima Bao made a claim to the throne but died before he could realize it, and his forces were subsequently crushed by Liu Yao in 320.

Safe from the chaos in the north, many northern officials flocked to serve under Sima Rui, and after Emperor Min's capture, the gentry clans backed him to take the throne.

The Jiankang regime was uninterested in helping Emperor Min reclaim northern China, or were genuinely too threatened by the refugee uprisings in Hubei and Hunan to avert their resources.

[29][30][31][32][33][34][35] 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.

[45][46][47][48][49] Han Chinese male nobles and royals of the southern dynasties who fled north to defect married over half of Northern Wei Xianbei Tuoba princesses.