八王之乱
By the end of the 4th century, the nomadic tribes had moved into the Guanzhong area, as well as the watersheds of the Wei and Xing rivers, practically surrounding the Jin capital in Luoyang. At the same time, the accession of Emperor Hui of Jin, who was possibly developmentally disabled, led to a struggle between the princes of the ruling Sima family to control him, sparking off the War of the Eight Princes.