Cao Rui's reign was a paradoxical one in many ways. He was clearly intelligent and capable, and yet never fulfilled his potential in his governance of the country or in his military campaigns. He showed great compassion at times, and yet was capable of great cruelty. He carried out many acts that were beneficial for the empire and yet at least as many that were hurtful. Despite his uncle
Cao Zhi's successive petitions, however, he continued the severe prohibitions against princes' holding of offices that his father Cao Pi had put in place, and this was commonly viewed by traditional historians as an eventual factor in the downfall of Cao Wei, as the Simas took power after Cao Rui's death without the imperial princes having any real ability to oppose them.
Treatment of officials Cao Rui, a young adult when he became emperor, quickly showed a knack for finding capable officials to empower while maintaining steady control over them. His father had appointed three regents for him—his distant cousin
Cao Zhen, the steady administrator
Chen Qun, and the shrewd strategist
Sima Yi. Once Cao Rui became emperor, however, he, while knowing the value of the advice of these senior officials, chose perhaps the best path to deal with them: honoring them and making them regional governors with full authority in the provinces they governed. By doing this, he showed that he was his own man while at the same time continued to receive the wisdom of their advice. Throughout Cao Rui's reign, he showed great diligence in seeking out advice from multiple officials, rather than concentrating on listening to several, before making important decisions. He was generally cautious and not willing to take risks, but at the same time was, therefore, able to avoid major disasters for his empire.
Campaigns against Shu Han One immediate threat that Cao Rui had to deal with after he became emperor were attacks from
Shu Han's chancellor,
Zhuge Liang. Zhuge had, after the death of Shu Han's founding emperor,
Liu Bei, initially taken a passive posture militarily with regards to the Shu Han-Cao Wei border, while re-establishing an alliance with Sun Quan's
Eastern Wu, in order to rest the people and the troops. In 227, he, under the theory that Shu Han was naturally a weaker state than Cao Wei and, if it had just sat and done nothing, would eventually be swallowed up by Cao Wei anyway, started a series of five northern campaigns. During these campaigns, Cao Rui's response generally was to head to the metropolitan
Chang'an—a politically important city that Wei could not afford to lose—and then commission generals to the frontlines to ward off Zhuge's attacks. This strategy had the effect of boosting the morale of the troops and shortening the communication line. Being fairly quickly updated as to the events at the frontlines, Cao Rui could also keep the central empire under his watch. Ultimately, Zhuge's campaigns were futile; after his death in 234, his plan was largely abandoned by his successors
Jiang Wan and
Fei Yi. However, that did not mean that there was peace on the borders with Shu Han, as nearly every year, there would be battles between the two states. However, there would be no major confrontations on the scale of Zhuge's campaigns for the rest of Cao Rui's reign.
Campaigns against Eastern Wu During Cao Rui's reign, there were also many battles waged against the other rival empire, Eastern Wu. The very first came only two months after Cao Rui had become emperor in June 226. It was during that campaign that Cao Rui showed his acumen for judging a situation correctly—believing that by the time that reinforcements could be sent, Eastern Wu's monarch Sun Quan would have already withdrawn, and therefore sending reinforcements was pointless. Throughout his reign, he would generally take a similar stance during campaigns against Eastern Wu as he did with Shu Han—head east personally to be close to the theater of the war, while remaining some distance away from the frontlines, which also proved to be effective. He also entrusted the southeastern border to the capable
Man Chong, and Man's stewardship averted many disasters. Cao Rui's greatest military loss came in 228, when the Eastern Wu general
Zhou Fang tricked Cao Rui's distant cousin and regional governor
Cao Xiu into believing that he was ready to surrender his troops to Cao Wei, while instead laying a trap for Cao Xiu. Instead of realizing that it was indeed a trap, Cao Rui enthusiastically approved Cao Xiu's plan, and this led to a major military disaster, but Cao Xiu's forces were saved by
Jia Kui from total annihilation. Another serious crisis posed by Eastern Wu occurred in 234, when Eastern Wu, in a semi-coordinated effort with Shu Han, launched an attack against Cao Wei simultaneously with
Zhuge Liang's Northern Expeditions. At the time, many frontline officials were on vacation visiting families, so Man Chong requested Cao Rui to call them back to fight Sun Quan. Cao Rui refused to cancel his subordinates' vacation, and ordered Man to focus on the defense. Cao Rui then personally led the royal army as reinforcement, and acted as an effective coordinator of the various forces that Cao Wei had on Eastern Wu's borders, and Eastern Wu was unable to make substantial gains.
Campaigns against Liaodong The only real military gain for Cao Wei during Cao Rui's reign was the end of the Gongsun clan's hold on Liaodong (modern central and eastern
Liaoning), which was started by
Gongsun Du in 190. In 228, Gongsun Du's grandson
Gongsun Yuan deposed his uncle
Gongsun Gong in a coup and asked for an official commission from Cao Rui. Acting against
Liu Ye ()'s advice to attack the Gongsuns while there was dissension within, Cao Rui instead gave Gongsun Yuan an official commission as governor of
Liaodong Commandery. In 232, Gongsun Yuan's repeated communicated with and sales of horses to
Eastern Wu angered Cao Rui, who ordered his generals
Tian Yu and Wang Xiong () to attack Liaodong against
Jiang Ji ()'s advice; the attacks were not successful, although Tian was able to intercept the Eastern Wu horse-buying fleet and destroy it. After the incident, although Gongsun formally maintained vassalage to Cao Wei, the relationship was damaged. The next year saw that relationship would be somewhat improved. Gongsun, apprehensive of another attack from Cao Wei, sent ambassadors to Eastern Wu to formally submit to its emperor Sun Quan. Sun was so pleased that he immediately created Gongsun the Prince of Yan and granted him the
nine bestowments, which were typically reserved for officials so powerful that the bestowments were typically viewed as a sign that the emperor was about to abdicate to them. However, Gongsun realized later that Eastern Wu would be of little help in an expedition against him. He betrayed Eastern Wu, slaughtered Sun's ambassadors as they arrived in Liaodong, and seized their troops. In response, Cao Rui created Gongsun the Duke of Lelang. In 237, Cao Rui once again considered attacking Liaodong, angered by reports that Gongsun had repeatedly defamed him. He commissioned
Guanqiu Jian to prepare for an attack, and then ordered Gongsun to come to Luoyang for an official visit. Gongsun refused and instead declared independence. Guanqiu attacked him, but was stopped by torrential rains. Gongsun then declared himself the Prince of Yan and entered into alliances with the
Xianbei tribes to harass Cao Wei's borders. The following year, Cao Rui sent Sima Yi with 40,000 men to attack Liaodong. Upon hearing this, Gongsun again requested aid from Eastern Wu. Sun, angry at Gongsun's previous betrayal, pretended to agree, but did not send Gongsun any actual help. Although Sima's expeditionary force was also initially halted by torrential rains as Guanqiu's was, Sima waited out the rains and eventually surrounded Gongsun's capital of
Xiangping (襄平, in modern
Liaoyang,
Liaoning), starving Gongsun's troops. After nearly three months of siege, Xiangping fell, and Gongsun fled, but was captured and executed by Sima. Liaodong became part of Cao Wei's domain.
Building projects and collection of concubines Almost immediately after Cao Rui ascended the throne, he started out large scale palace and temple-building projects. Part of it was to be expected—the Luoyang palaces had been remnants of the ones not destroyed by
Dong Zhuo, and the temples were needed for the cults of his ancestors. However, he went beyond the minimally required, and continued to build temples and palaces throughout the rest of his reign, severely draining the imperial treasury. While he occasionally halted projects at the officials' behest, the projects would restart after brief breaks. He not only built palaces in Luoyang, but also built a palace in
Xuchang. In 237, he further moved many of the magnificent statues and monuments that were commissioned by
Emperor Wu of Han from Chang'an to Luoyang, costing great expenses and lives. He further built gigantic bronze statues of his own and placed them on a man-made hill inside his palace, surrounded by rare trees and plants and populated by rare animals. Cao Rui was also increasing his collection of women, as his concubines and ladies in waiting numbered thousands. His palace-building projects might have been with intent to house them. The contemporary historian
Yu Huan recorded that in 237, Cao Rui even ordered that beautiful married women all be formally seized unless their husbands were able to ransom them, and that they would be married to soldiers instead—but that the most beautiful among them would become his concubines. Despite some officials' (including Zhang Mao's) protestations, this decree was apparently carried out, much to the distress of his people.
Marriages, succession issues and death When Cao Rui became emperor, it was commonly expected that his wife, Princess Yu, would be created empress, but she was not. Rather, he created a favorite concubine,
Consort Mao, empress in late 227. Princess Yu was exiled back to their original palace. He loved Empress Mao dearly, and a number of her relatives, including her father and brother, became honored officials (but without actual powers). Despite his collection of women, however, Cao Rui was without any son who survived infancy. He adopted two sons to be his own—
Cao Fang and
Cao Xun, whom he created princes on 23 September 235. In June or July 237, Cao Rui took the unprecedented (and unrepeated in Chinese history) action of setting his own temple name of
Liezu, while setting the temple names of Cao Cao and Cao Pi. He also ordered that the temples of Cao Cao, Cao Pi and himself were not to be torn down in the future. He carried out these actions apparently in apprehension that he would be given an unflattering temple name (or none at all) and that his temple would eventually be destroyed, due to his lack of biological issue and unclear origin. By 237, Cao Rui's favorite was no longer Empress Mao, but
Consort Guo. In September that year, when Cao Rui was attending a feast hosted by Consort Guo, Consort Guo requested that Empress Mao be invited to join as well, but Cao Rui refused and further ordered that no news about the feast is to be given to Empress Mao. However, the news leaked, and Empress Mao talked about the feast with him anyway. He became exceedingly angry, and killed a number of his attendants whom he suspected of leaking the news to Empress Mao, and, inexplicably, ordered Empress Mao to commit suicide, even though she was still buried with honors due an empress, and her family remained honored. On 31 December 238, Cao Rui grew ill. He created Consort Guo empress on 16 January 239 in preparation of allowing her to become empress dowager after his death. He initially wanted to entrust his adopted son, Cao Fang the Prince of Qi, to his uncle
Cao Yu, to serve as the lead regent, along with Xiahou Xian (),
Cao Shuang, Cao Zhao (; son of
Cao Xiu), and
Qin Lang (). However, his trusted officials Liu Fang () and Sun Zi () were unfriendly with Xiahou and Cao Zhao and were apprehensive about their becoming regents, and managed to persuade him to make Cao Shuang (with whom they were friendly) and Sima Yi regents instead. Cao Yu, Cao Zhao, and Qin were excluded from the regency. On 22 January 239, Cao Rui created the seven-year-old Cao Fang crown prince, and died that same day. Cao Fang succeeded him as emperor. On 17 February, Cao Rui was buried at Gaoping Tombs.
Oddities regarding traditions and customs Even before his setting of his own temple name, Cao Rui was recorded to be involved in odd behaviour in events regarding the traditions and customs of his day. After he became emperor, Cao Rui once attempted to tug at
Empress Dowager Guo's clothing as he begged her to play some music; Lady Guo was well-known for her playing of the
pipa. At the time,
Yang Fu was by his side; he then asked the emperor, "The Empress Dowager is Your Majesty's
dimu; where is your decorum?" Ashamed, Cao Rui withdrew his hand. After Lady Guo left, the emperor said to Yang, "I know you emphasize greatly on proper behavior. But I am indeed feeling troubled. Now that I have listened to you, isn't it like standing beside the flowing waters of the
Xiang River and being unable to see that person?" On 3 August 229,
Cao Teng was posthumously honoured as "Emperor Gao of Wei" (), becoming the only eunuch in
Chinese officialdom to have this honor. When Cao Rui's daughter Cao Shu (曹淑) died in infancy (less than one month old) on 15 February 232, Cao Rui insisted on taking part in the funeral procession. Yang Fu noted that he did not do so during the funerals of Cao Pi and
Empress Dowager Bian, and advised him not to join in the funeral procession. Cao Rui ignored Yang's advice. Cao Rui also insisted that the funeral rites used be those for an adult woman and that court officials were to don mourning clothing;
Chen Qun wrote a formal submission to advise the emperor. Cao Rui ignored the advice. Afterwards, besides bestowing upon Cao Shu the posthumous title of "Princess Yi of Pingyuan", Cao Rui ordered that a temple be raised for her. A deceased grandson of his mother Lady Zhen's brother, Zhen Huang (甄黄), was also buried with Cao Shu and was posthumously made a marquis. A male relative of Empress Mingyuan, Guo De (郭德), was declared to be the deceased couple's child; his surname was changed to "Zhen" and he was made Marquis of Pingyuan, inheriting the princess's title.
Changes to the calendar during the ''Jing'chu'' era In February 237, after receiving reports of auspicious signs, Cao Rui agreed to make changes to the calendar, such that the ''jian'chou
month (the 12th month) became the new zheng
month (and thus the start of a new year). This calendar change took effect after 11 April 237 in the Julian calendar, along with the change in era name from Qing'long
to Jing'chu''. After Cao Rui's death, his successor
Cao Fang reverted the changes, and the ''jian'yin
month (the 1st month) once again became the zheng'' month, and thus the start of a new year. ==Era names==