The "Great Unity" established by Tang Zhisheng is another expansion after the Han Dynasty, and its history is usually called "Han and Tang Dynasties". Tang, defeated the northwest Turkic, made Anxi its capital; In the northeast, Goguryeo was completely defeated, and Anton Duhu was established, and Heishui Duhu was established far away in Heilongjiang to govern the northeast. Kaiyuan is extremely prosperous, and its territory far exceeds that of the Western Han Dynasty.

The unprecedented unification of Han and Tang Dynasties is two important historical periods of China's territorial expansion.

Under the condition of "great unification", we have achieved long-term stability, steady development of production, sufficient food and substantial national treasury. During the Kaiyuan and Tianbao years of the Tang Dynasty, every family had several years of grain reserves, which were "too old to be measured".