What is the full name of the person acknowledged by Emperor Xuānzong as jiedushi military governor of the new Guiyi Circuit?
The last great ambitious ruler of the Tang dynasty was Emperor Xianzong (r. 805–820), whose reign was aided by the fiscal reforms of the 780s, including a government monopoly on the salt industry. He also had an effective well trained imperial army stationed at the capital led by his court eunuchs; this was the Army of Divine Strategy, numbering 240,000 in strength as recorded in 798. Between the years 806 and 819, Emperor Xianzong conducted seven major military campaigns to quell the rebellious provinces that had claimed autonomy from central authority, managing to subdue all but two of them. Under his reign there was a brief end to the hereditary jiedushi, as Xianzong appointed his own military officers and staffed the regional bureaucracies once again with civil officials. However, Xianzong's successors proved less capable and more interested in the leisure of hunting, feasting, and playing outdoor sports, allowing eunuchs to amass more power as drafted scholar-officials caused strife in the bureaucracy with factional parties. The eunuchs' power became unchallenged after Emperor Wenzong's (r. 826–840) failed plot to have them overthrown; instead the allies of Emperor Wenzong were publicly executed in the West Market of Chang'an, by the eunuchs' command.
However, the Tang did manage to restore at least indirect control over former Tang territories as far west as the Hexi Corridor and Dunhuang in Gansu. In 848 the ethnic Han Chinese general Zhang Yichao (799–872) managed to wrestle control of the region from the Tibetan Empire during its civil war. Shortly afterwards Emperor Xuānzong of Tang (r. 846–859) acknowledged Zhang as the protector (防禦使, Fangyushi) of Sha Prefecture and jiedushi military governor of the new Guiyi Circuit.
Zhang Yichao