End of the Han dynasty
The end of the Han dynasty refers to the period of Chinese history from 189 to 220 AD, which roughly coincides with the tumultuous reign of the Han dynasty's last ruler, Emperor Xian. During this period, the country was thrown into turmoil by the Yellow Turban Rebellion (184–205). Meanwhile, the Han Empire's institutions were destroyed by the warlord Dong Zhuo, and fractured into regional regimes ruled by various warlords, some of whom were nobles and officials of the Han imperial court. Eventually, one of those warlords, Cao Cao, was able to gradually reunify the empire, ostensibly under Emperor Xian's rule, but the empire was actually controlled by Cao Cao himself. Cao Cao's efforts to completely reunite the Han empire were rebuffed at the Battle of Red Cliffs in 208 / 209, when his armies were defeated by the allied forces of Sun Quan and Liu Bei. The Han dynasty formally ended in 220 when Cao Cao's son and heir, Cao Pi, pressured Emperor Xian into abdicating in his favour. Cao Pi became the emperor of a new state, Cao Wei. A year later, in response to Cao Pi's usurpation of the Han throne, Liu Bei declared himself emperor of Shu Han; and in 229, Sun Quan followed suit, declaring himself emperor of Eastern Wu. The period from Emperor Xian's abdication in 220 to the partial reunification of China under the Jin dynasty in 265 was known as the Three Kingdoms era in Chinese history.
Emperor Wu of Han
Emperor Wu is considered one of the greatest emperors in Chinese history, due to his effective governance which made the Han dynasty one of the most powerful nations in the world. Michael Loewe called the reign of Emperor Wu the "high point" of "Modernist" (classically justified Legalist) policies, looking back to "adapt ideas from the pre-Han period." His policies and most trusted advisers were Legalist, favouring adherents of Shang Yang. However, despite establishing an autocratic and centralised state, Emperor Wu adopted the principles of Confucianism as the state philosophy and code of ethics for his empire and started a school to teach future administrators the Confucian classics. These reforms had an enduring effect throughout the existence of imperial China and an enormous influence on neighbouring civilizations.