The weather in Tubo is getting warmer.

Tubo troops invaded Chang 'an, wantonly burned and looted, and committed all kinds of evils, supporting a princess's younger brother as a puppet emperor. However, this situation only lasted for half a month, and then the Tubo army retreated for various reasons.

The first is the correct command of Guo Ziyi. Guo Ziyi actively recruited soldiers on the way. Although he encountered obstacles on the way, he also recruited thousands of troops. Although thousands of people can't compare with the 200,000 troops of the Tubo army. However, Guo Ziyi deployed a large number of troops in Chang 'an and won the support of the people, which made the Tubo army think that Guo Ziyi was an army to crusade, so the Tubo army retreated without a fight.

The second reason is the Tubo side. Tubo troops were originally stationed in western Shaanxi, and then attacked Chang 'an. They fought for a long time, and the goal was not to occupy Chang 'an, but to enter Chang 'an to burn, kill and plunder. Chang 'an is too far away from Tubo, and they can't be stationed after shooting down.

Tubo has also been at war for years, and domestic contradictions have long been constant. They don't have enough manpower, material resources and financial resources to support the occupation of Chang 'an. After all, Chang 'an was the political center of the Tang Dynasty. Although it has declined, the thin camel is bigger than the horse. Therefore, Tubo did not intend to occupy Chang 'an from the beginning, and it was for this reason that he supported a puppet to be emperor.

Although Tubo withdrew his troops, he did not stop attacking the Tang Dynasty. Every year after that, Tubo sent troops to attack the Tang Dynasty and plundered a lot of property. Guo Ziyi, the general at that time, said that Tubo was a snot and a tear, and Tang Gaozu could no longer trust military commanders, which also weakened the resistance to Tubo.