Excerpts from Books and Wikipedia
"Historians generally regard the Tang as a high point in Chinese civilization, and a golden age of cosmopolitan culture. . . . The Tang capital at Chang'an (present-day Xi'an) was the most populous city in the world in its day. . . . Besides political hegemony, the Tang also exerted a powerful cultural influence over neighboring East Asian states such as those in Japan and Korea. The Tang dynasty was largely a period of progress and stability in the first half of the dynasty's rule, until the devastating An Lushan Rebellion (755–763) and the decline of central authority in the latter half of the dynasty. . . . Buddhism became a major influence in Chinese culture . . . However, in the 840s the Emperor Wuzong of Tang enacted policies to persecute Buddhism, which subsequently declined in influence. [Wikipedia] "The Tang capital at Chang'an became a great international metropolis, a focal point of the Eurasian world. Between 600 and 900 no Western capital could compete in size and grandeur . . . . Under the Emperor Xuanzong (who reigned from 713 to 755) the Tang reached its height of prosperity and grandeur . . . They were defeated by Arab forces in 751 near Samarkand." [Fairbank: China, p. 78-82]