At the end of the Three Kingdoms Period, Sima family became prominent in the Wei. In 265 AD, Sima Yan ( 司马炎 ) ， the descendants of the great historian Sima Qian ( 司马迁 ) ， usurped the power and founded a new dynasty Jin. They also conquered the Wu, thus ending the period of The Three Kingdoms . Jin was historically divided into two periods: the Western Jin ( 西晋 ) with Luoyang ( 洛阳 ) as its capital city and Eastern Jin ( 东晋 ) as Jiankang ( 建康 ) ( present Nanjing ) became the capital city .

After defeating the Wu ( 东吴 ) in AD 280 , there was no longer a serious danger of being invaded. Therefore, the Jin emperor declared the armies should be disbanded, and returned. However, this did not occur in every region. The princes, most of whom had been given their titles due to their relationship to the emperor, declared they needed personal guards, so they sold these discharged soldiers belonging mainly to the state. This was a fatal mistake of the Jin government, as it made them virtually powerless, while all their rivals and enemies gained power.

After the death of Si-ma Yan, there was never again a strong leader. The leaders and princes were often assassinated in the struggle for power. During this time, the Chinese people surrounding the capital suffered due to the fighting and began a migration out from the center of the empire to the more peaceful frontier regions. Although providing a brief period of unity after conquering the The Wu , the Jin could not contain the invasion and uprising of nomadic peoples after the devastating War of the Eight Princes ( 八王之乱 ) .

The Jin was eventually defeated by the Huns ( 匈奴 ) , who claimed they were descendents of the Han Dynasty because of the Han princesses given to them in marriage. However, they never succeeded in forming a true dynasty and uniting China . Rather, the disunity continued with the Northern and Southern dynasties ( 南北朝 ) . The defeated Jin fled and from 317 AD-420 AD they ruled as the Eastern Jin in Nanking . The Eastern Jin was the first of a couple of dynasties ( Southern Dynasties ) that developed a culture different from that of northern China . As an economical center of whole China , the south should be of great importance for the whole of China until today.