Gao Xianzhi
The Tang captured the vital route through the Gilgit Valley from Tibet in 722, lost it to the Tibetans in 737, and regained it under the command of the Goguryeo-Korean General Gao Xianzhi. When the An Lushan Rebellion ended in 763, the Tang Empire withdrew its troops from its western lands, allowing the Tibetan Empire to largely cut off China's direct access to the Silk Road. An internal rebellion in 848 ousted the Tibetan rulers, and Tang China regained its northwestern prefectures from Tibet in 851. These lands contained crucial grazing areas and pastures for raising horses that the Tang dynasty desperately needed.