During the Tang dynasty,China is known as the most stable and civilized country. The national territory and cultural traditions laid by the ""Zhenguan governance"" in Tang Dynasty are far beyond surpassing of that in any times of peace and prosperity afterward. In the first half of Tang Dynasty, with its developed economy and advanced culture, China becomes the biggest exporter of culture and technology to its neighboring countries. The inclusive social environment provides all ethnic groups with an opportunity for extensive exchanges and integrations. The national might of the Tang Dynasty reaches its peak at the last year of the reign of Emperor Kaiyuan, after which it begins to decline. Finally, the Rebellion of An Lushan and Shi Siming in 755 AD witnesses a watershed in the history of Tang Dynasty. The most remarkable literary achievement of the Tang Dynasty is Tang Poetry, with its endless famous poets in different styles. The poem culture reaches an insurmountable peak in the Tang Dynasty.