Lasting some four hundred years and larger at its height than contemporary imperial Rome, the Han was the first great empire, one that experienced a flowering of culture and a major impetus to push out frontiers and open them to trade, people and new ideas. In doing so it defined the national identity to such an extent that the main body of the Chinese people still style themselves " Han Chinese " after this dynasty.

Liu Bang maintained the Qin model of local government, but to prevent others from repeating his own military takeover, strengthened his position by handing out large chunks of land to his relatives. This secured a period of stability, with effective taxation financing a growing civil service and the building of a huge and cosmopolitan capital, Chang'an , at today's Xi'an. Growing revenue also refuelled the expansionist policies of later ruler Wu . From 135 to 90 BC he extended his lines of defence well into Xinjiang and Yunnan, opening up the Silk Road for trade in tea, spices and silk with India, west Asia and Rome. He used his sons and competent generals to beat off northern tribes, enter Korea, and to subdue and colonize the unruly southern states, including Guangdong and even parts of Vietnam. At home Wu stressed the Confucian model for his growing civil service, beginning a two-thousand-year institution of Confucianism in government offices.

But, eventually, the empire's resources and supply lines were stretched to breaking point, while the burden of taxation led to unrest and retrenchment. Gradually the ruling house became decadent and was weakened by power struggles between rival factions of imperial consorts, eunuchs and statesmen, until Wang Mang , regent for a child emperor, usurped the rule to found his own brief dynasty in 9 AD. Fifteen years later the Eastern Han was re-established from a new capital at Luoyang, where the classical tradition was re-imposed under Emperor Liu Xiu , though after his reign the dynasty was again gradually undermined by factional intrigue. Internal strife was later fomented by the Yellow Turbans , who drew their following from Taoist cults, while local governments and landowners began to set up as semi-independent rulers, with the country once again splitting into warring states. But by this time two major schools of philosophy and religion had emerged to survive the ensuing chaos. Confucianism's ideology of a centralized universal order had crystallized imperial authority; and Buddhism , introduced into the country from India, began to enrich aspects of life and thought, especially in the fine arts and literature, while itself being absorbed and changed by native beliefs.