Emperor Xian of Han
Cao Cao died on 15 March 220. His son and successor, Cao Pi, soon forced Emperor Xian to abdicate the throne in favour of himself, ending the Han dynasty. Cao Pi established a new state known as Cao Wei (sometimes known inaccurately as the Kingdom of Wei), and he granted Emperor Xian a noble title – Duke of Shanyang (山陽公). The former Emperor Xian died in 234 and was buried with honours befitting an emperor, using Han ceremonies, and the then emperor of Wei, Cao Rui, was one of the mourners. As Emperor Xian's crown prince was already dead, his grandson Liu Kang (劉康) inherited his dukedom, which lasted for 75 more years and two more dukes, Liu Jin (劉瑾) and Liu Qiu (劉秋), until the line was exterminated by invading Xiongnu tribes in about 309, during the Jin dynasty. This practice of an emperor conferring hereditary nobility on his predecessor, from whom he usurped the throne, was known as "er wang san ke" (二王三恪).
Jian'an poetry
The term "Jian'an poetry" covers the final years at the end of the Han Dynasty and during which the Cao family was rising, or risen, to prominence were known as the "Jian'an" era (196-220), the final reign era of Emperor Xian of Han: the following period is known as the Three Kingdoms era, due to the three kingdoms which divided up the Han Dynasty, and war with one another for succession to the Han empire. A prominent Han dynasty general, Cao Cao effectively took control of the Han dynasty from the Liu imperial family, and following Cao Cao's death, his son Cao Pi formalized this by accepting the abdication of the last titular ruler of Han and establishing the Cao family as the ruling dynastic family of a new state, Wei (also known as Cao Wei), one of the Three Kingdoms which were successor states to the Han empire. Besides their role as leaders in war and politics, the Cao family also had an important role in the field of poetry and literature.