The Tang Dynasty is universally recognized as one of the most glorious periods in China. It has seen great progress in many fields. The territory in the Tang Dynasty, acquired through military expansion, was greater than that in the Han Dynasty. Great advances have been made in agriculture and irrigation tools, making a prosperous agricultural economy. In business, the Tang Dynasty had trade contacts with more countries. The Tang Dynasty was also the golden age of literature and arts. In the high Tang period, there appeared a whole generation of literary giants including Li Bai and Du Fu, the twin masters of the Tang poetry.