From Wikipedia

Engineering China

The Han Dynasty (202 BCE – 220 CE) emerged in 206 BCE, with its founder Liu Bang proclaimed emperor in 202. It was the first dynasty to embrace the philosophy of Confucianism, which became the ideological underpinning of all regimes until the end of imperial China. Under the Han Dynasty, China made great advances in many areas of the arts and sciences. Emperor Wu (Han Wudi 漢武帝/汉武帝) consolidated and extended the Chinese empire by pushing back the Xiongnu (sometimes identified with the Huns) into the steppes of modern Inner Mongolia, wresting from them the modern areas of Gansu, Ningxia and Qinghai. This enabled the first opening of trading connections between China and the West, the Silk Road. Han Dynasty general Ban Chao expanded his conquests across the Pamirs to the shores of the Caspian Sea. The first of several Roman embassies to China is recorded in Chinese sources, coming from the sea route in 166, and a second one in 284.

Nevertheless, land acquisitions by elite families gradually drained the tax base. In CE 9, the usurper Wang Mang (王莽) founded the short-lived Xin ("New") Dynasty (新朝) and started an extensive program of land and other economic reforms. These programs, however, were never supported by the land-holding families, for they favored the peasants. The instability brought about chaos and uprisings.

Emperor Guangwu (光武帝) reinstated the Han Dynasty with the support of land-holding and merchant families at Luoyang, east of Xi'an. This new era would be termed the Eastern Han Dynasty. Han power declined again amidst land acquisitions, invasions, and feuding between consort clans and eunuchs. The Yellow Turban Rebellion (黃巾之亂/黄巾之乱) broke out in 184, ushering in an era of warlords. In the ensuing turmoil, three states tried to gain predominance in the Period of the Three Kingdoms. This time period has been greatly romanticized in works such as Romance of the Three Kingdoms.