ABSTRACT
In November of 763, scarcely a year after the termination of the great rebellion, a large Tibetan army suddenly advanced against the Tang capital of Chang’an. Descending rapidly into the Wei River valley from the northwest, the Tibetans defeated an inferior Tang force at Zhouzhi, about thirty miles west of the capital, on November 12. The very next day the emperor (now Daizong, who had succeeded his father Suzong in the middle of 762) decamped for the relatively safe haven of Shanzhou, on the road to Luoyang. On November 18 the Tibetans entered the city and installed an elderly cousin of Daizong on the imperial throne. They proceeded to plunder the palace and the city, setting fires as they went. Dispersed Tang troops took the opportunity to join in the looting, while much of the populace sought refuge in the hills to the south of the city. The Tibetans were not, however, in a position that was tenable for the long term. Recalled from retirement to deal with the crisis, the great loyalist general Guo Ziyi rallied Tang troops at Shangzhou and moved on Chang’an from the southeast by way of the Wu Pass, while other Tang commanders brought their troops down from the prefectures immediately to the north of the Wei River valley. With Tang forces gathering around them, the Tibetans evacuated the city on November 30, dragging a large number of women, scholars, and craftsmen into captivity, but abandoning their puppet emperor of twelve days to his fate. The capital was secured by Tang troops in December, and Daizong returned to his palace early in 764.1
The temporary loss of Chang’an was a dramatic indicator of the extent to which Tang power had been diminished by the An Lushan rebellion. The immediate opening for the Tibetan advance was created by the defection of a key fortress guarding the valley of the Jing River, but the groundwork had been prepared over the course of several years. As veteran Tang troops were recalled from the western frontier to be thrown into the struggle against the rebels, the ambitious Tibetan ruler Khri-srong-lde-brtsan threw his forces against the greatly weakened Chinese defenses. Each year, more towns fell to the Tibetans. Most of the Longyou region was eventually overrun, and the frontier shifted more than 150 miles to the east. Even after the Tibetans retreated from the Tang capital in 763, they remained entrenched on the
headwaters of the Wei and Jing rivers, still within striking distance of Chang’an.2 The areas north and west of the capital were disturbed by Tibetan incursions throughout the the 760s and 770s, and the threat would not be removed until the collapse of the Tibetan state in the middle of the ninth century.
