Cao Ju was a son of Cao Cao, a warlord who rose to prominence towards the end of the Han dynasty and laid the foundation for the Cao Wei state. His mother was Lady Huan, a concubine of Cao Cao. He had two full brothers: Cao Chong and Cao Yu. In 211, Cao Ju was enfeoffed as the "Marquis of Fanyang" by Emperor Xian, the figurehead emperor of the Han dynasty under Cao Cao's control. In 217, his title was changed to "Marquis of Wan". In 220, following Cao Cao's death, Cao Ju's half-brother Cao Pi usurped the throne from Emperor Xian, ended the Han dynasty, and established the Cao Wei state with himself as the new emperor. Cao Pi first enfeoffed Cao Ju as a duke in 221, but promoted him to a prince under the title "Prince of Zhangling" in 222. Later in 222, he changed Cao Ju's title to "Prince of Yiyang". Sometime between 222 and 224, he changed Cao Ju's title to "Prince of Pengcheng" and relocated him to Pengcheng, where Cao Ju's mother Lady Huan was living. Later, he changed Cao Ju's title to "Prince of Jiyin". In 224, Cao Pi issued an edict to reform the nobility system by reducing the sizes of princedoms from commanderies to counties. Cao Ju's title was thus changed to "Prince of Dingtao ". In 232, after Cao Ruirestored the nobility system to the previous one, Cao Ju became the "Prince of Pengcheng " again. In 237, Cao Ju had 2,000 taxable households removed from his princedom as punishment after he was found guilty of ordering the manufacture of restricted items. Cao Rui also issued an imperial edict to reprimand Cao Ju for his conduct. The 2,000 taxable households were returned to him in 239. Throughout the reigns of the subsequent Wei emperors, the number of taxable households in Cao Ju's princedom increased until it reached 4,600.
Family
Cao Ju had at least three sons. One of them, Cao Cong, was designated as the heir of Cao Ju's elder brother Cao Chong, because Cao Chong died early and had no son to succeed him. The other two, Cao Fan and Cao Chan, were consecutively designated as the heirs of Cao Zizheng, a half-brother of Cao Ju, because Cao Zizheng too died early and had no son to succeed him.
