the Yangtze. In 581, the Prime Minister of Northern Zhou, Yang Jian, usurped the throne and founded the Sui dynasty (581-618) as Emperor Wen of Sui. His son, Emperor Yang of Sui, annihilated the Chen dynasty (557-589) and unified northern and southern China, thereby bringing an end to the Southern and Northern Dynasties era. Over the course of this period, the Xianbei who entered into China were immersed among the Chinese and later classified into "Han". Yet, not all branches of the Xianbei shared this fate. In the 3rd and 4th centuries, Tuyühu, a branch of the Murong Xianbei, undertook a westward migration that allowed them and those who followed them to develop in a different path. Westward migration The separation of Tuyühu from the Murong Xianbei occurred during the Western Jin dynasty (265-316), which succeeded the Cao Wei (220-265) in northern China. Legends accounted the separation to be due to a fight between his horses and those of his younger brother, Murong Wei. The actual cause was intense struggle over the Khanate position and disagreement over their future directions. The fraction that supported Murong Wei into the Khanate position aimed at ruling over China, whereas Tuyühu intended to preserve the Xianbei culture and lifestyles. The disagreement resulted in Tuyühu to proclaim as the Khan, or Kehan, and undertook the long westward journey under the title of the Prince of Jin, or Jin Wang, followed by other Xianbei and Wuhuan groups. While passing through western Liaoning and Mt. Bai, more Xianbei groups joined them from the Duan, Yuwen, and Bai sections. At the Hetao Plains near Ordos in Inner Mongolia, Tuyühu Khan led them to reside by Mt. Yin for over thirty years, as the Tuoba Xianbei and Northern Xianbei joined them through political and marriage alliances. After settling down in the northwest, they established the powerful Tuyühu Empire named to his honor as the first Khan who led them there, by subjugating the native peoples who were summarily referred to as the "Qiang" and included more than 100 different and loosely coordinated tribes that did not submit to each other or any authorities. After Tuyühu Khan departed from the northeast, Murong Wei composed an "Older Brother’s Song," or "the Song of A Gan:" "A Gan" is Chinese transcription of "a ga" for "older brother" in the Xianbei language. The song lamented his sadness and longing for Tuyühu. Legends accounted