Tuyuhun

Tuyuhun (Chinese: 吐谷渾; LHC: *tʰɑʔ-jok-guən; Wade-Giles: T'u-yühun), also known as Henan (Chinese: 河南) and Azha (Tibetan: ཨ་ཞ་, Wylie: ‘A-zha; Chinese: 阿豺), was a dynastic monarchy established by the nomadic peoples related to the Xianbei in the Qilian Mountains and upper Yellow River valley, in modern Qinghai, China.

After the disintegration of the Xianbei state, nomadic groups were led by their khagan, Murong Tuyuhun (慕容吐谷渾; 246–317), to the rich pasture lands around Qinghai Lake about the middle of the 3rd century AD.

Murong Tuyuhun was the older brother of the Former Yan's ancestor Murong Hui and elder son of the chanyu Murong Shegui (慕容涉歸) of the Murong Xianbei who took his people from their original settlements on the Liaodong Peninsula to the Yin Mountains, crossing the Yellow River between 307 and 313, and into the eastern region of modern Qinghai.

The Tuyuhun Empire was established in 284 by subjugating the native peoples referred to as the Qiang, including more than 100 different and loosely coordinated tribes that did not submit to each other or any authority.

After Tuyuhun died in Linxia, Gansu in 317, his sixty sons further expanded the empire by defeating the Western Qin (385–430) and Xia (407–431) kingdoms. The Qinghai Xianbei, Tufa Xianbei, Qifu Xianbei and Haolian Xianbei joined them. They moved their capital 6 kilometres (3.7 mi) west of Qinghai Lake.

These Xianbei groups formed the core of the Tuyuhun Empire and numbered about 3.3 million at their peak. They carried out extensive military expeditions westward, reaching as far as Hotan in Xinjiang and the borders of Kashmir and Afghanistan, and established a vast empire that encompassed Qinghai, Gansu, Ningxia, northern Sichuan, eastern Shaanxi, southern Xinjiang, and most of Tibet, stretching 1,500 kilometres (930 mi) from east to west and 1,000 kilometres (620 mi) from north to south. They unified parts of Inner Asia for the first time in history, developed the southern route of the Silk Road, and promoted cultural exchange between the eastern and western territories, dominating the northwest for more than three and half centuries until it was destroyed by the Tibetan Empire. For most of its history, Tuyuhun existed as an independent state.

During the beginning of the Tang dynasty, the Tuyuhun Empire came to a gradual decline and was increasingly caught in the conflict between the Tang and the Tibetan Empire. Because the Tuyuhun controlled the crucial trade routes between east and the west, the empire became the immediate target of invasion by the Tang.

The Tibetan Empire developed rapidly under the leadership of Songtsen Gampo, who united the Tibetans and expanded northward, directly threatening the Tuyuhun Empire. Soon after he took the throne of the Yarlung Kingdom in Central Tibet in 634, he defeated the Tuyuhun near Qinghai Lake and received an envoy from the Tang. The Tibetan emperor requested marriage to a Tang princess, but was refused. In 635–636 the Emperor Taizong of Tang defeated the Tibetan army; after this campaign, the Emperor Taizong agreed to provide a Tang princess to Songtsen Gampo.