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.
Cao Zizheng
In 220, Cao Zizheng's half-brother Cao Pi became the first emperor of the Cao Wei state after usurping the throne from Emperor Xian, the last emperor of the Han dynasty. The following year, he honoured Cao Zizheng with the posthumous title "Duke Dai of Mei" (郿戴公), and ordered Cao Fan (曹範), a son of Cao Ju, to be Cao Zizheng's heir. In 222, Cao Pi enfeoffed Cao Fan as the Marquis of Pingshi (平氏侯), but changed his title to Marquis of Chengwu (成武侯) in the following year. In 229, Cao Pi's successor, Cao Rui, promoted Cao Fan from a marquis to a duke. Cao Fan died in 235 without a son to succeed him, and was posthumously honoured as "Duke Dao" (悼公). In 236, Cao Rui ordered Cao Chan (曹闡), Cao Fan's younger brother, to be Cao Fan's heir. Cao Chan thus became the new Duke of Mei (郿公). Throughout the reigns of the subsequent Wei emperors, the number of taxable households in Cao Chan's dukedom increased until it reached 1,800.