An Lushan Rebellion
In 754 Tang forces defeated Baltistan (Greater Bolü) and Tibetan forces. In 755 the An Lushan Rebellion occurred and the Tang dynasty withdrew 200,000 soldiers from the Western Regions to protect the capital. In 763 the Tibetan Empire conquered Yanqi. In the same year the Tang capital was briefly taken by the Tibetans before they were forced to retreat.