It is unknown when Cao Shuang was born. When young, he was considered prudent and steady among the Cao clansmen. When Cao Rui was still
his father's heir, he favored Cao Shuang greatly. After ascending the throne in June 226, Cao Rui bestowed upon Shuang several titles of increasing seniority and prestige over his reign. When Shuang's father Cao Zhen died in 231, Shuang inherited his father's peerage and marquisate as the Marquis of Shaoling (邵陵侯). Around 239, when the Wei emperor
Cao Rui became critically ill, he resolved to pass the throne to his adopted son,
Cao Fang. He initially wanted to entrust Cao Fang to his uncle
Cao Yu, to serve as the lead regent, along with Xiahou Xian (夏侯獻), Cao Shuang, Cao Zhao (曹肇; son of
Cao Xiu) and
Qin Lang. However, his trusted officials
Liu Fang (劉放) and
Sun Zi (孫資), who were unfriendly with Xiahou Xian and Cao Zhao, became apprehensive upon hearing that Cao Rui wanted to appoint them as regents. They managed to persuade the dying emperor to appoint Cao Shuang (with whom they were friendly) and
Sima Yi (who was then with his troops at Ji County (汲縣; in present-day
Xinxiang, Henan) as the regents instead. Cao Yu, Cao Zhao and Qin Lang were excluded from the regency. As a result, Cao Shuang came to power in the final days of Cao Rui's reign. However, Cao Shuang was clearly inadequate for the important task assigned to him. When Cao Rui asked if he was competent enough, Cao Shuang was so nervous that he was unable to speak, so Liu Fang stepped on his foot and whispered into his ear, urging him to say: "I will serve the dynasty to my death." Despite his inability, Cao Shuang and his brothers, Cao Xi (曹羲) and Cao Xun (曹訓), wielded great power in Wei. He was also often at odds with his co-regent
Sima Yi, who had greater influence and support. In 243, Sima Yi's position was further strengthened by another successful deployment:
Zhuge Ke, a general of Wei's rival state,
Eastern Wu, was constantly sending agents to Shouchun (壽春; around present-day
Shou County,
Anhui) to prepare an invasion, so Sima Yi led Wei forces to Shu County (舒縣), Lujiang Commandery (盧江郡) near the Wei–Wu border. Upon hearing the news, the Wu emperor
Sun Quan immediately ordered Zhuge Ke to withdraw to Chaisang (柴桑), Yuzhang Commandery (豫章郡). Sima Yi's popularity and influence instantly multiplied as he was cheered as being able to scare away the enemy numbering over 100,000 without a fight and thus secured the border and saved Shouchun from certain attack. Cao Shuang, feeling insecure over Sima Yi's triumph, managed to persuade the emperor Cao Fang to promote Sima Yi to the position of Grand Tutor (太傅). While it was ostensibly a promotion for Sima Yi, the position of Grand Tutor was in fact an honorary one without any real authority over military affairs. Cao Shuang was desperate for a victory to boost his own fame so he selected
Shu Han, Wei's other rival state, as his target. Leading an army numbering over 100,000 troops, Cao Shuang invaded Shu territory in March 244. However, two months later, he lost to Shu forces led by
Wang Ping and
Fei Yi at the
Battle of Xingshi and barely escaped back to
Chang'an. Cao Shuang's popularity and influence dropped to a new low after his defeat. At the same time, Sima Yi's popularity and influence further increased due to his opposition to the campaign from the start. Potentially to deceive Cao Shuang into letting down his guard, Sima Yi stopped engaging in any political activity in May 247 and retired on the grounds of illness. He went on further to pretend to be ill and senile. In the same year, Cao Shuang followed the advice of
Li Sheng,
Deng Yang and
Ding Mi in order to maintain his power. In the winter of 248, Cao Shuang's protégé,
Li Sheng, was appointed as the Inspector of
Jing Province by the Wei imperial court. Before he left
Luoyang to assume office in Jing Province, Cao Shuang sent him to check on Sima Yi. Cao Shuang and his followers overjoyed when Li Sheng reported that Sima Yi was indeed ill and that he could not even hear what Li Sheng said. According to Li Sheng, Sima Yi misheard "Jing Province" as "
Bing Province". Cao Shuang sensed that Sima Yi no longer posed a threat to him and started to lower his guard against the latter. On 5 February 249, Cao Shuang and his two brothers, Cao Xi (曹羲) and Cao Xun (曹訓), left the imperial capital
Luoyang to accompany the emperor Cao Fang to pay respects to his ancestors at the Gaoping Tombs (高平陵). After that, they proceeded to go on a hunting expedition outside Luoyang. ==Execution==