[Yun]

The formidable Tie'le general Pugu Huai'en fought under Guo Ziyi during the An Lushan rebellion, but immediately after the rebellion he was falsely accused of conspiring with the Uyghurs to rebel. Because of this he did rebel, and eventually got the Uyghurs, Tibetans, Tuyuhun and Tangut on his side. He attacked the Chang'an region two times within three months in 764, but was forced to retreat both times (the first time because his vanguard was defeated, the second time because Tang troops attacked his home base at Lingwu). In 765, he struck at Chang'an a third time with several tens of thousands of troops from the Uyghurs, Tibetans, Tuyuhun and Tangut, but suddenly fell ill and died. Guo Ziyi was then able to persuade the Uyghurs to switch sides and attack the Tibetans, defusing the crisis.

If Pugu Huai'en had not died of illness, could he have succeeded where An Lushan and Shi Siming did not?

[snowybeagle]

Well, the accounts I read of Guo ZiYi's solo ride into the Uyghurs made the presumption that the Uyghurs were deceived into thinking Guo ZiYi had died.

Was the regard for Guo ZiYi so high among the Uyghurs?
Or was a fiction created to boost Guo ZiYi's image?

[Yun]

Guo Ziyi had fought alongside the Uyghurs during the An-Shi rebelion, and they had much reason to be impressed by him. From official accounts, we know that he was over 2.1m tall, and topped the Martial Examinations which included tests of physical strength and archery. He was probably the only person they respected more than Pugu Huai'en.

But then, Li Siye is also described in the histories as being about 2m tall, so there might be an element of myth-making there.

[Yun]

I just remembered that in 763, the Tibetans actually took Chang'an and installed a puppet emperor, forcing Tang Daizong to flee. However, they could not sustain their occupation, and withdrew leaving the puppet emperor to be defeated by the Tang government. Further evidence of how a Tibetan alliance with Pugu Huai'en could have succeeded in starting a new dynasty n Chang'an.