Family background and ascension to the throne
Cao Mao was born in 241, the son of Cao Lin , the Prince of Donghai, who was the son of Cao Wei's first emperor Cao Pi, making him the cousin of Cao Fang, the emperor at the time of his birth. In 244, at age three, in accordance with Cao Wei's regulations that the sons of princes were to be created dukes, he was created the Duke of Gaoguixiang. When he was young, he became known for his intelligence and studiousness.
In 249, Cao Mao's father Prince Cao Lin died. Cao Mao was eight. His older brother Cao Qi became the Prince of Donghai.
By 254, the governance of the empire was firmly in the hands of the Simas, whose patriarch Sima Yi had seized power from Cao Fang's regent Cao Shuang in 249. After Sima Yi's death in 251, the Simas were led by his son Sima Shi. In 254, after falsely accusing the emperor's father-in-law Zhang Ji and Zhang's associates Li Feng and Xiahou Xuan of treason, Sima Shi had them and their clans executed, and when Cao Fang considered a coup against the Simas later that year, Sima Shi had him deposed.
It was at this time that Cao Fang's stepmother made a last ditch attempt at preserving Cao Wei's imperial authority, by injecting herself into the process of selecting the next emperor. When Sima Shi notified her that he intended to make Cao Pi's brother Cao Ju , the Prince of Pengcheng, emperor, she managed to persuade him that such a succession would be improper -- that since Cao Ju was the uncle of her husband Cao Rui, such a succession would leave Cao Rui effectively sonless with no heir. Sima Shi was forced to agree with her, and he made, as she suggested, Cao Mao emperor instead. When Sima Shi asked her for the imperial seal, she again reasoned with him and refused politely, under the reasoning that she had met Cao Mao before and wanted to personally hand him the seal. When Cao Mao was summoned to the capital, he acted in accordance with the ceremonies due a duke, rather than putting on imperial pretensions immediately, until he was enthroned. This earned him popular support and praise as a humble young emperor.
Reign: domination by the Simas
Despite Empress Dowager Guo's intentions and Cao Mao's own intelligence, however, they made very little impact in trying to stem the tide of the Simas' growing power. In 255, the general Guanqiu Jian, the commander in the important eastern city of Shouchun, along with another general Wen Qin, raised a rebellion against the Simas, but were quickly crushed by Sima Shi's forces. Guanqiu was killed, and his clan was slaughtered. Wen and his sons fled to Eastern Wu.
Sima Shi, however, was already ill when Guanqiu and Wen started the rebellion, and he grew sicker during the campaign and died less than a month after the defeat of Guanqiu and Wen, at Xuchang. In the aftermaths of Sima Shi's death, the 14-year-old emperor made an effort to regain imperial power. With Sima Shi's brother and heir Sima Zhao also at Xuchang, Cao Mao issued an edict which, under the rationale that Sima Shi had just defeated Guanqiu and Wen's rebellion and that the southeastern empire was still not complete pacified, ordered Sima Zhao to remain at Xuchang and that Sima Shi's assistant Fu Gu return to the capital Luoyang with the main troops. Under Fu and Zhong Hui's advice, however, Sima Zhao returned to Luoyang anyway against edict, and was able to maintain control of the government. Indeed, from that point on, he would not let Cao Mao or Empress Dowager Guo to be out of his control.
Also in 255, Cao Mao created his wife empress.
In the next few years, Cao Mao was further known for his diligent studies. He gradually established a circle around him -- a number of officials who were unquestioned in their support of the Simas, but who might also have something to gain from allegiance to the emperor, including Sima Zhao's cousin Sima Wang, Wang Chen , Pei Xiu, and Zhong Hui, all of whom were known for their literary talent. By doing this, he was hoping that he could minimize suspicion against him but at the same time gradually win their heart. He often met with them to discuss literature, and, because Sima Wang lived farther from the palace than the others, he gave Sima Wang a fast two-wheeled wagon and five imperial guardsmen as escorts.
As it became clearer that Sima Zhao had designs on the throne, the general Zhuge Dan, who succeeded Wuqiu as the commander at Shouchun, became uneasy. When Sima Zhao sent his associate Jia Chong to Shouchun to discuss military matters with Zhuge and Jia probed whether Zhuge could support a Sima takeover -- which Zhuge sternlly rebuke Jia about. After Jia returned to Luoyang, he advised Sima to summon Zhuge back to the capital under the guise of promoting him to Prime Examiner , and Sima did so. Zhuge, in response, declared a rebellion and sought help from Eastern Wu . Sima acted swiftly and quickly surrounded Shouchun, but not until an Eastern Wu detachment led by Wen entered the city to help its defense. However, the main Eastern Wu forces, under the command of the powerful but incompetent general Sun Lin, failed to advance on Shouchun, and was of little help to Zhuge. By spring 258, Zhuge and Wen were trapped inside the city, and they got into an argument as to proper strategy. Zhuge killed Wen, whose sons then defected to Sima, leading to the fall of the city. Zhuge was captured and killed, along with his clan, except for his son Zhuge Jing , who had been sent as a messenger to Eastern Wu. After Zhuge's failure, no other general or official dared to resist Sima's might. Cao Mao became desperate, and in 259, after reports of discovery of yellow dragons in two wells, Cao Mao commented that it was actually a sign of divine ''disfavor'' and wrote the following poem, entitled ''The Ode to the Hidden Dragon'' :
:''The poor dragon is trapped, alone and cold;''
:''He cannot leap out of the depths;''
:''He cannot rise to the heavens;''
:''He cannot even descend onto fields.''
:''The poor dragon fell into the deep well;''
:''Even catfish dance before him;''
:''He hides his teeth and claws and sighs;''
:''And I am this depressed as well.''
This greatly displeased Sima Zhao, who paid more attention to the emperor's activities afterwards.
Also in 258, under pressure from Sima, Cao Mao issued an edict granting him the nine bestowments -- a sign of impending usurpation -- and while Sima declined, it became even clearer what his intentions were.
Attempted coup against Sima Zhao and death
In 260, at age 19, Cao Mao was forced to again issue an edict granting Sima Zhao the nine bestowments, which Sima declined again, but which drew Cao Mao's ire. He gathered his associates Wang Chen, Wang Jing , and Wang Ye and told them that, while he knew the chances of success were slight, he was going to act against Sima Zhao. He stated that he was willing to die if needed -- but that he felt he has some chance of success. Despite urging from Wang Jing to call it off as a sure disaster, he went into the palace to report to Empress Dowager Guo his intentions; Wang Chen and Wang Ye fled to report to Sima, but Wang Jing, despite his opposition to the plan, did not desert.
Cao Mao then led the imperial guards and servants and, arming himself with a sword, set out to head for Sima's mansion. Sima Zhao's brother Sima Zhou tried to resist, but after Cao Mao's attendants yelled loudly, Sima Zhou's forces deserted. Jia Chong then arrived and intercepted the imperial troops. Cao Mao fought personally, and Jia Chong's troops, not daring to attack the emperor, were also deserting, when one of the officers under Jia's command, Cheng Ji , after asking Jia what to do and was told by Jia to defend the Sima power regardless of the consequences, took a spear and killed Cao Mao with it.
After Cao Mao's death, public sentiments called for Jia's death, but what Sima Zhao did first was to force Empress Dowager Guo to posthumously demote Cao Mao to common citizen status and order that he be buried as such. He also executed Wang Jing and his clan. The next day, after pleas from his uncle Sima Fu, Sima Zhao instead had Empress Dowager Guo order that Cao Mao be demoted back to duke but buried with the ceremonies of an imperial prince. Sima Zhao then summoned Cao Huang , the Duke of Changdaoxiang and a grandson of Cao Cao to the capital to become the emperor; by now, Empress Dowager Guo was powerless to speak further. 19 days later, however, Sima Zhao publicly accused Cheng and his brothers of treason and had them and their clan executed, to appease public sentiment, while sparing Jia.
** Cao Lin , Prince Ding of Donghai, son of Cao Pi