The Han dynasty began with the defeat of the Qin army in 206 B.C. by the Han and their leader, Liu Bang. The Chinese people had suffered under the Legalist rule of the Qin emperors and rebellion had begun with the death of the first Qin emperor, and only four years into the rule of the second Qin emperor, the empire fell to the Han.
The Han dynasty is divided into three parts: The Western or Former Han dynasty (206 BCE - 9 CE), the Xing dynasty (the interregnum of Wang Mang, lasting from 9-25 CE), and the Eastern or Later Han dynasty (25-220 CE). In fact, the Former and Later Han dynasties were separate, but as the Eastern dynasty was created by a relative of the founder of the Western, they are often considered to be two parts of a single dynasty.
The most notable effort of the Han dynasty was that of achieving a unified Chinese philosophy. While the Qin tried to achieve this aim by squelching any thoughts not in keeping with their ambitions, including those of Kong Zi (Confucious) and Lao Zi (Lao Tzu), the Han formed a syncretic philosophy. It was first during Han rule that such concepts as the dao, yin and yang, and the five elements began to be thought of as underlying all events in the universe.
Thus, the Han developed the first fusion of the somewhat disparate ideas developed during the much earlier Warring States period. The Han were the beginning of the tradition of rigorously factual history, imbuing it with discussions of the dao and with their humanist idea that although people behave selfishly and hurt others, they do so because of depraved social and economic conditions. Virtue in government should engender virtue in populace, according the the Han, and thus their extreme attention to proper government, as in the Confucian ideal, as opposed to the government-of-force that Legalism and the Qin proposed.
The Former Han Dynasty
After the death of Qin Shihuangdi, the first Qin emperor and the last with any ability to govern, various generals and nobles vied for power. Liu Bang, not a noble but a commoner (a peasant farmer, in fact), was the general who gained control of the Wei River, the homeland of the Qin. He built his capital at Chang'an and began the process of reunifying China, entitling himself "Han Gao Su", or Exalted Emperor. He was the first emperor of the Han Dynasty.
The most important change in Han government was the eventual adoption of Confucianism as its official philosophy, along with the Confucian idea that government belonged only to the moral, which led to civil service examinations and rule of those that merited it. Another defining feature of the Han was the encouragement of academics. Confucian ideals encouraged education, in contrast to those of the Qin, who did not encourage scholarship very greatly. Education was seen as a way of reducing the power of the nobility, and all of these changes resulted in a bureaucracy much different from that of the Qin,
The Han dynasty greatly enlarged the dominion of China. During the zenith of Han rule, under Wu Ti's reign (141-87 BCE), China was almost as large as it is now, and included parts of Korea, Vietnam, and most of Mongolia.
The Han empire, in its great size, used taxes as an instrument to control its far-flung territories. The wealthy and powerful managed to avoid paying taxes, while the poor faced a heavier and heavier burden. Eventually, the poor were unhappy and the rich, forming alliances through marriage and obtaining greater power than the emperor himself. In 22 BCE active revolt broke out. Wang Mang, the regent who ruled for the infant Han emperor, was declared emperor by court officials.
Wang Mang's rule was the interregnum known as the Xing Dynasty. Because of his status as unrelated to the Han rulers, it was given the status of a separate dynasty in between the two halves of the Han period.
The Later Han Dynasty
For the two years between Wang Mang's death and the foundation of the Later Han dynasty, China was in chaos. In 25 AD, wealthy landowner Liu Xu assumed the throne, declaring the Han dynasty to be restored, with the new capital of Luoyang. He reestablished the strong central government of the Qin and Former Han Dynasties and pursued agrarian reforms. The later Han then achieved an aggressive military expansion.
In 50 CE the Han government allied itself with some of the Xiongnu tribes and eventually marched across the Gobi desert, attacking the northern Xiongnu tribes. These tribes then migrated into Central Asia and Russia, and eventually to Europe, where they were known as the Huns. This military expansion allowed enough control over inner Asia to establish the Silk Road, connecting China to Rome through trade. At this point, China's military influence reached much of Central Asia and Chinese traders traveled as far as Asia Minor.
Economic power, much as in the Former Han dynasty, soon allowed wealthy landowning nobles to keep their own armies and avoid taxes, weakening the government. The peasants began to bear more than their share of the tax burden and eventually formed radical secret societies to fight the Han government. The Yellow Turbans, a secret Taoist society in eastern China brought down the Later Han government in 220 CE and the Chinese empire separated into the Three Kingdoms. | 
