The Tang dynasty (A.D. 618-907), with its capital at Chang'an, is regarded by historians as a high point in Chinese civilization--equal, or even superior, to the Han period.
Its territory, acquired through the military exploits of its early rulers, was greater than that of the Han. Stimulated by contact with India and the Middle East, the empire saw a flowering of creativity in many fields. Buddhism became a permanent part of Chinese traditional culture. Block printing was invented, making the written word available to vastly greater audiences.
The Tang period was the golden age of literature and art. A government system supported by a large class of Confucian literati selected through civil service examinations was perfected under Tang rule.
By the middle of the eighth century A.D., Tang power had ebbed. Domestic economic instability and military defeat in 751 by Arabs, marked the beginning of five centuries of steady military decline for the Chinese empire.
Thanks for this information, but as I know the Arabs reach to the west border of China and never plunge into. An agreement signed between them and till now a minority of Arab descendants are living in China.