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Conquest by the Tang

Although the Göktürk Khaganate once provided support to the Tang dynasty in the early period of the civil war during the collapse of the Sui dynasty, the conflicts between the Göktürks and Tang finally broke out when Tang was gradually reunifying China proper. The Göktürks began to attack and raid the northern border of the Tang Empire and once marched their main force of 100,000 soldiers to Chang'an, the capital of Tang. The emperor Taizong of the Tang, in spite of the limited resources at his disposal, managed to turn them back. Later, Taizong sent his troops to Mongolia and defeated the main force of Göktürk army in Battle of Yinshan four years later and captured Illig Qaghan in 630 AD. With the submission of the Turkic tribes, the Tang conquered the Mongolian Plateau. From then on, the Eastern Turks were subjugated to China.

After a vigorous court debate, Emperor Taizong decided to pardon the Göktürk nobles and offered them positions as imperial guards. However, the proposition was ended by a plan for the assassination of the emperor. On 19 May 639 Ashina Jiesheshuai and his tribesmen directly assaulted Emperor Taizong of Tang at Jiucheng Palace (九 成 宮, in present-day Linyou County, Baoji, Shaanxi). However, they did not succeed and fled to the north, but were caught by pursuers near the Wei River and were killed. Ashina Hexiangu was exiled to Lingbiao. After the unsuccessful raid of Ashina Jiesheshuai, on 13 August 639 Taizong installed Qilibi Khan and ordered the settled Turkic people to follow him north of the Yellow River to settle between the Great Wall of China and the Gobi Desert. However, many Göktürk generals still remained loyal in service to the Tang Empire.