Guo Ziyi - Under Emperor Daizong and Tibetan Invasion

Under Emperor Daizong and Tibetan Invasion

Not long after, Suzong died and was succeeded by his son Daizong. The new emperor was worried about Guo Ziyi's fame and called him back to Chang'an. Guo Ziyi advised the emperor to take a note of the threat posed by the Tibetans, but the emperor largely ignored this.

The "Battle" of Chang'an

In 763, an invading force of perhaps one hundred thousand Tibetans penetrated China so far as to surround the capital city, Chang'an. This height of Tibetan power was also a height of Guo's career. Guo ordered cavalry scouts to go forward and light fires, in places which the Tibetans could see, and to then retreat. Guo also sent secret messages to Chang'an, ordering citizens to strike gongs and shoot off fireworks. The Tibetans, confused by these actions, panicked, scattering when the rumor spread that Guo Ziyi moved against them with a large force. With the Tibetans retreating from their positions, the battle was concluded without loss to either side. Many Chinese military historians considered this victory to be the best example of Sun Tzu's idea of the cleanest kind of battle, "a war with no loss on either side but simply played out with the desired effect for the victor." There are discrepancies in the number of cavalry troops Guo dispatched; some Chinese texts state that Guo had sent out only thirteen scouts, but a Tibetan text source indicated there had been two hundred. Nevertheless, it was a great victory, and when Guo Ziyi arrived at Chang'an with his "large" force, Daizong appeared to him and stated, "By employing the Elder not sooner: so many deaths reached, woe is this!" 「用卿不早，故及於此。」

The Tibetan threat of 765 and the Uyghur alliance

The next two years were peaceful, but the Tibetans attacked again in 765, when the Uyghur Jiedushi Pugu Huai'en sent false messages to the King of Tibet stating that Guo Ziyi had died. The Tibetan king was eager to avenge his earlier defeat, and dispatched a large force to attack Tang China again. Various Uyghur chieftains, also believing that Guo was dead, joined force with the Tibetans. The Tibetan force was recorded as more than thirty thousand (including a few thousand of Uyghurs), almost the entire Tibetan military at the time.

When news of the Tibetans reached Emperor Daizong, he sent Guo Ziyi out with a few thousand men. When Guo was within a day's march from the enemy, he decided to go alone to see the Uyghur chieftains. His officers and son Guo Xi (郭晞) were so dismayed and panicked by his intention that they would not let go of his horse's reins, declaring such an act would be suicide. Guo laughed and convinced his officers to let him go, but his son would not. Angered, Guo whipped his son's hand so that he released the reins, reprimanding him and telling him that this was a life and death situation for the empire; their force was small and if they fought the Tibetans alone, both father and son, and their troops, would die. If he succeeded in his plan the empire would be defended, but if it failed only his own life would be lost.

When Guo arrived at the Uyghur's camp, he did not reveal his identity and appeared to be a messenger who had been sent to tell them that Guo Ziyi was coming to see them. The Uyghur chieftains, many of who had joined the rebel side in the An Shi Rebellion, were surprised and panicked to hear that Guo was alive, deciding that they had to meet with him. Guo laughed at them and asked them why they would want to face Guo Ziyi again after their defeat at his hands during the An Shi Rebellion. The Uyghur chieftains replied they had been told that he was dead, but if they met with him and saw he was alive, they would retreat. Guo, however, insisted that Guo Ziyi did not seek their retreat but instead wanted them to join him against the Tibetans. The Uyghur chieftains, saying they had been deceived by the Tibetans about Guo's death, decided to break the alliance with them. They even claimed that shamans had foretold that a great man would lead them to victory and that they now believed this man must be Guo, and agreed to join forces with the Tang.

Battle of Xiyuan

Guo returned to his camp and ordered a thousand light horsemen to made a quick rush at the Tibetan camp at Xiyuan. When the Tibetans realized the Uyghurs had broken their alliance, they tried to withdraw, but Guo's horsemen arrived and scattered their forces; at the same time, the Uyghurs arrived and prevented the Tibetans' retreat. Over ten thousand Tibetans were killed in battle and another ten thousand were taken as prisoners of war. Guo continued to pursue the Tibetans and freed over four thousand civilians they had taken captive.

When the Tibetan king heard that his force had been defeated, he quickly sent a message to Emperor Daizong seeking a peace, stating that his army had been on a hunting trip and had had no intention of attacking the Tang Empire. Although Daizong did not believe this, he agreed to the peace and Tibet was never again a threat to China.