A qaghan of the Western Turkic Khaganate is assassinated in a Chinese palace by Eastern Turkic rivals after the approval of Tang emperor Gaozu.
The Tang campaigns against the Western Turks, known as the Western Tujue in Chinese sources, were a series of military campaigns conducted by the Tang dynasty against the Western Turkic Khaganate in the 7th century AD. Early military conflicts were a result of the Tang interventions in the rivalry between the Western and Eastern Turks in order to weaken both. Under Emperor Taizong, campaigns were dispatched in the Western Regions against Gaochang in 640, Karasahr in 644 and 648, and Kucha in 648.
The wars against the Western Turks continued under Emperor Gaozong, and the khaganate was annexed after General Su Dingfang's defeat of Qaghan Ashina Helu in 657. The Western Turks attempted to capture the Tarim Basin in 670 and 677, but were repelled by the Tang. The Second Turkic Empire defeated the fragmented Western Turks in 712, and absorbed the tribes into the new empire.
The areas controlled by Tang Empire came under the dynasty's cultural influences and the Turkic influence of the ethnically Turkic Tang soldiers stationed in the region. Indo-European prevalence in Central Asia declined as the expeditions accelerated Turkic migration into what is now Xinjiang. By the end of the 657 campaign, the Tang had reached its largest extent. The Turks, Tibetans, Muslim Arabs and the Tang competed for control over Central Asia until the collapse of the Tang in the 10th century.