The Tang Dynasty was the most prosperous dynasty in China and the pride of the entire Han civilization. Before the Anshi Rebellion, Tang used an army of 550,000 to stand up to no less than 2 million foreign troops around it, which showed the prosperity of its force. The glory of the early Tang Dynasty and the flourishing Tang Dynasty is indeed proud, but the strength of the Middle and Late Tang Dynasty has long been lost...
After the Anshi Rebellion, the division of feudal towns, foreign invasions, eunuch dictatorship, partisan disputes, and peasant uprisings, various factors the strength of the Tang Empire has long gone. The Tang Dynasty originally had only one empty shelf left in the central government, and the tang emperors in various localities had long been ignored until 907 AD, when Zhu Wen ordered Li Zhuchan to let go, and the Tang Dynasty collapsed.
After the fall of the Tang Dynasty, no government in the interior could take over the vast and fragmented territory it had left behind. The war zones have openly declared their independence in areas where they have them. As a result, China fell into a state of division for 73 years, and it was not until 979 AD that it was unified by the emerging Song Dynasty, but the Song Dynasty could not restore the golden age that lasted forever.
As for the Western Regions, after the Tang Dynasty quelled the Anshi Rebellion, its strength had been weakened, and the Western Regions were cut off by Tubo and slowly encroached upon, until 808 AD, when all the Western Regions fell into the hands of Tubo. And the Anxi Capital Protectorate became a word that appeared in the history books of the Tang Dynasty.
Comparing the maps of the Qin Dynasty and the Song Dynasty, we will find that in fact, there is not much difference in size between the two, and the territory of the Song Dynasty is only the approximate extent of the Qin Dynasty in the third century BC. The demise of the Tang Dynasty also lost more than 1,000 years of China's territorial expansion.