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Sima Yi

Sima Yi

Chinese general, politician and regent
Sima Yi
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Quick Facts

Intro Chinese general, politician and regent
A.K.A. Yi Sima, Sima Yi(2)
Is Politician
From China
Type Politics
Gender male
Birth 179, Wen County, People's Republic of China
Death 251, Luoyang, People's Republic of China
Father: Sima Fang
Siblings: Sima FuSima Lang司馬馗
Spouse: Zhang ChunhuaMiss Bai
Children: Sima LunSima ShiSima ZhaoSima JingSima ZhouSima GanSima RongSima JunSima LiangPrincess NanyangPrincess Gaoliu
Peoplepill ID sima-yi
The details


Sima Yi (  Chinese: 司馬懿; 179 – 7 September 251), courtesy name Zhongda, was a Chinese military general, politician, and regent of the state of Cao Wei during the Three Kingdoms period of China.

He formally began his political career in 208 under the Han dynasty's Imperial Chancellor Cao Cao; quickly rising through the ranks. His success in both handling domestic and military affairs, such as in governance and the promotion of agriculture, serving as a capable adviser, repelling incursions and invasions led by Shu and Wu forces, speedily crushing Meng Da's rebellion, and conquering the Gongsun-led Liaodong commandery, all managed to garner him great prestige over the decades. He is perhaps best known for defending Wei from a series of invasions between 231 and 234 led by Wei's rival state Shu.

In 239, he was made to preside as a regent for the young Cao Fang—after the latter's adoptive father, Cao Rui, had died—along with another co-regent, Cao Shuang. Although amicable at first, the relationship soon deteriorated in light of Cao Shuang's corruption, extravagance, and attempts to curtail Sima Yi's political influence. In 249, after carefully planning and building up support, he ousted Cao Shuang from power in a coup d'état and had him and his associates executed.

Sima Yi would go on to serve as the de facto primary authority in Wei after this event, although in 251 he faced some opposition in the form of Wang Ling's rebellion, which he swiftly dealt with. He died later that year, on 7 September 251, at the age of 71 or (more likely) 72, with his eldest son, Sima Shi, succeeding his position.

For the remainder of Wei's history, state power would increasingly rest in the hands of the Sima clan, which paved the way for the establishment of the Jin dynasty, which was founded by Sima Yi's grandson, Sima Yan, in 266. After Sima Yan became emperor, he honoured his grandfather with the posthumous title Emperor Xuan of Jin (宣皇帝) and the temple name Gaozu (高祖).

Family background

Sima Yi's ancestral home was in Xiaojing Village (孝敬里), Wen County (溫縣), Henei Commandery (河內郡), which is in present-day Zhaoxian Town, Wen County, Henan. His ancestor was Sima Ang, the King of Yin (殷王), who was briefly a ruler of one of the Eighteen Kingdoms during the transition period from the Qin dynasty to the Western Han dynasty, before Liu Bang's general, Han Xin, conquered his territory, capturing him and his capital city based in Zhaoge (朝歌; present-day Qi County, Hebi, Henan) in the process. In the early Han dynasty, Sima Ang's former kingdom, which had been largely situated in Henei (河內; in present-day northern Henan), became a commandery of the Han Empire, and his descendants had lived there since.

Sima Jūn (司馬鈞), an eighth-generation descendant of Sima Ang, and the great-great-grandfather of Sima Yi, served as a general of the Han Empire; holding the position of General Who Conquers the West (征西將軍). Sima Jūn's son, Sima Liang (司馬量), held the position of Grand Administrator of Yuzhang (豫章太守), and Sima Liang's son, Sima Jùn (司馬儁), served as Grand Administrator of Yingchuan (潁川太守). Sima Jùn's son, Sima Fang, served as the Prefect of Luoyang (洛陽令), Intendant of Jingzhao (京兆尹), and later in his life as Cavalry Commandant (騎都尉) towards the end of the Eastern Han dynasty. Sima Yi (Zhongda) was Sima Fang's second son.

Sima Yi had one elder brother, Sima Lang (Boda), and six younger brothers (in decreasing order of seniority): Sima Fu (Shuda), Sima Kui (Jida), Sima Xun (Xianda), Sima Jin (Huida), Sima Tong (Yada), and Sima Min (Youda). The eight Sima brothers were collectively known as the "Eight Das" because their courtesy names all ended with da (達).

Early life

Sima Yi displayed intelligence and great ambitions at a young age. He was knowledgeable and well-versed in Confucian classics. When chaos broke out in China towards the end of the Eastern Han dynasty, Sima Yi often expressed sympathy and concern for the people. Before he reached adulthood around the age of 19, Sima Yi once met Yang Jun (楊俊), a commandery administrator who was known for spotting talents. Yang Jun described him as an "extraordinary talent". Cui Yan, a friend of Sima Yi's elder brother, Sima Lang, once said: "(Sima Yi) is intelligent, decisive, and unique. (Sima Lang) can't be compared to him."

Sima Yi and his family used to live in the imperial capital, Luoyang, where his father, Sima Fang, served as a government official. Sima Yi was raised in a strict Confucian manner: He was not allowed to visit his father unless summoned, to speak to his father without being explicitly addressed, and neither was he allowed to be seated in the same room as his father. In 190, when the warlord Dong Zhuo dominated the Han central government and wanted to relocate the imperial capital to Chang'an, Sima Fang ordered Sima Lang to bring the Sima family out of Luoyang and return to their ancestral home in Wen County, Henei Commandery. Some months later, as Sima Lang foresaw that chaos would break out in Henei Commandery, he relocated his family to Liyang Commandery (黎陽郡; around present-day Xun County, Henan), where they stayed with Sima Lang's kinsman, Zhao Weisun. In 194, when war broke out between the warlords Cao Cao and Lü Bu, Sima Lang brought his family out of Liyang Commandery and again returned to their now-ravaged ancestral home in Wen County, Henei Commandery, where Sima Yi and his brothers largely sustained themselves by living as farmers; fending off local groups of bandits while studying diligently during their free time.

Around 201, the administrative office of Henei Commandery nominated Sima Yi to serve in the government by holding local office, possibly as a clerk in charge of the records, and in 202 he was sent as a Reporting Officer (上計掾) to the capital. Around the same year, he married a woman named Zhang Chunhua, possibly at the instigation of his father. At the same time, the warlord Cao Cao, who then held the position of Minister of Works in the Han imperial court, heard of Sima Yi's talent and wanted to recruit him to serve in the administration. Sima Yi declined, presumably on grounds of illness, with the Book of Jin more specifically mentioning that he, seeing that the Han Empire's future was bleak, declined and lied by supposedly saying that he suffered from paralysis; staying at home, with Cao Cao's spies reporting that they saw Sima Yi lying motionless in bed.

One day—in a story that may be apocryphal—while Sima Yi was drying his books under the sun, there was a sudden downpour, so he rushed out to grab his books and was seen by a maid. Sima Yi's wife, Zhang Chunhua, feared that the maid would leak out news that Sima Yi was well and get their family into trouble, so she killed the maid to silence her.

Service under Cao Cao

When Cao Cao became the Imperial Chancellor in 208, he sent an official to recruit Sima Yi to serve as an assistant clerk in his administration. He also allegedly instructed the official to arrest Sima Yi if he dawdled. Sima Yi apparently became afraid, so he accepted the appointment. Although he was initially assigned to be an attendant to the crown prince, he was later reassigned to other positions, including Gentleman of the Yellow Gate (黃門侍郎), Consultant (議郎), Officer in the East Bureau of the Imperial Chancellor's Office (丞相東曹屬), and Registrar in the Imperial Chancellor's Office (丞相主簿).

Advising Cao Cao to attack Yi Province

In 215, Sima Yi accompanied Cao Cao on his campaign against the warlord Zhang Lu, whom Cao Cao defeated in Hanzhong Commandery at the Battle of Yangping, and afterwards Sima Yi urged him to capitalise on the momentum to press on and attack his rival, Liu Bei, who was in the neighbouring Yi Province (covering present-day Sichuan and Chongqing). Sima Yi pointed out that since Liu Bei had only recently seized control of Yi Province from Liu Zhang, he had yet to establish a strong foothold in the province. However, Cao Cao rejected Sima Yi's idea and said that he was already content with having Longyou (隴右; covering parts of present-day Gansu and Shaanxi). He then turned his attention towards his other key rival, Sun Quan.

Urging Cao Cao to usurp the throne

Sun Quan sent an emissary to meet Cao Cao, requesting to make peace and expressing his willingness to pledge allegiance to Cao Cao. He also urged Cao Cao to seize the throne from Emperor Xian and declare himself emperor. In response to Sun Quan's suggestion, Cao Cao remarked: "This rascal wants me to put myself on top of a fire!" However, Sima Yi told him: "The Han dynasty is in decline. Your Lordship controls nine-tenths of the Han Empire. You are in a position to take the throne. Sun Quan's submission is the will of Heaven. Previously, during Yu's time and throughout the Xia, Shang, and Zhou dynasties, the rulers who did not hesitate when they should take the throne were the ones who truly understood Heaven's will." Cao Cao ultimately never usurped the throne from Emperor Xian and remained nominally a subject of the Han Empire until his death.

In 216, after Emperor Xian promoted Cao Cao from a duke to a vassal king under the title "King of Wei" (魏王), Sima Yi became an adviser to Cao Cao's son and heir apparent, Cao Pi. Cao Pi highly regarded and respected Sima Yi for his brilliance. Along with Chen Qun, Wu Zhi, and Zhu Shuo (朱鑠), Sima Yi was one of Cao Pi's close aides and one of his "Four Friends". Before Cao Pi became his father's heir apparent in 216, he engaged in a power struggle against his younger brother Cao Zhi over the succession. During this time, Sima Yi was believed to be among those who secretly backed Cao Pi and helped him win the position of heir apparent. He also allegedly had a hand in Cao Zhi's demotion and removal from politics after Cao Pi became the emperor.

When Sima Yi was appointed as an Army Major (軍司馬), he suggested to Cao Cao to stockpile food supplies and maintain their defences at the same time because there were more than 200,000 people who were unable to sustain themselves through farming. Cao Cao accepted his idea and implemented a policy for the people to farm and stockpile grain.

Battle of Fancheng

Sima Yi also warned Cao Cao about Hu Xiu (胡修) and Fu Fang (傅方), who respectively served as the Inspector of Jing Province and the Administrator of Nanxiang Commandery (南鄉郡; in Jing Province) at the time. He said that Hu Xiu was violent while Fu Fang was arrogant, so they should not be entrusted with the important responsibility of guarding the border at Jing Province. Cao Cao ignored him. In 219, during the Battle of Fancheng, while Cao Cao's general Cao Ren was besieged by Liu Bei's general Guan Yu in Fancheng (樊城; present-day Fancheng District, Xiangyang, Hubei), Cao Cao ordered Yu Jin to lead reinforcements to lift the siege on Fancheng. However, the reinforcements were destroyed in a flood and Yu Jin surrendered to Guan Yu. As Sima Yi foresaw, Hu Xiu and Fu Fang defected to Guan Yu, placing Cao Ren in an even more perilous situation.

Upon learning of Yu Jin's defeat, Cao Cao felt that the Han imperial capital, Xuchang, was too near enemy territory, so he considered moving the capital further north into Hebei. Sima Yi and Jiang Ji said: "Yu Jin's defeat was not due to flaws in our defences, nor would it significantly affect us. Moving the imperial capital is showing our weakness to the enemy. It will cause panic in the regions around the Huai and Mian rivers. Sun Quan and Liu Bei seem close to each other, but they actually don't trust each other. Sun Quan will feel very uneasy upon seeing Guan Yu's victory, so we should incite him to attack Guan Yu's base in Jing Province. This will lift the siege on Fancheng." Cao Cao heeded their advice. Sun Quan later sent his general Lü Meng to attack Gong'an County and invade Jing Province in the winter of 219–220. Guan Yu was captured and executed by Sun Quan's forces.

Cao Cao wanted to relocate residents in Jing Province and Yingchuan Commandery (潁川郡) further north as he felt that they were too close to enemy territory in the south. Sima Yi, however, advised him against doing so and said: "The Jing and Chu regions are unstable. The people are easy to move but hard to pacify. As Guan Yu has been recently defeated, bad people will go into hiding. If we move the good people, we might cause them to feel distressed and unwilling to return to our side." Cao Cao heeded Sima Yi's advice. The people affected by the Battle of Fancheng later managed to revert to their original livelihoods before the battle.

When Cao Cao died in Luoyang in March 220, there was much apprehension in the imperial court. Sima Yi supervised the funerary arrangements to ensure that everything was going to be carried out in an orderly fashion, and thereafter accompanied the funeral cortège to Ye (present-day Handan, Hebei), whereby in doing so he earned the respect of officials both within and outside the central government.

Service under Cao Pi

After Cao Pi succeeded his father as the (vassal) King of Wei (魏王) and Imperial Chancellor of the Han Empire in early 220, he enfeoffed Sima Yi as the Marquis of Hejin Village (河津亭侯) and appointed him as his Chief Clerk (長史).

Later, when Sun Quan led his forces to attack Cao Pi's territories in Jing Province, some officials rejected the idea of resisting Sun Quan since Fancheng (樊城; present-day Fancheng District, Xiangyang, Hubei) and Xiangyang lacked food supplies. At the time, Cao Ren, who was defending Xiangyang, had been reassigned from Fancheng to defend Wancheng (宛城; present-day Wancheng District, Nanyang, Henan). Sima Yi said: "Sun Quan has recently defeated Guan Yu. At this time, he will be thinking of defending his newly acquired territories (rather than attacking us), so he will definitely not pose a threat to us. Xiangyang's land and water routes are crucial to its defences against enemy attacks, so we cannot abandon the city." Cao Pi ignored Sima Yi's advice. As Sima Yi predicted, Sun Quan did not attack them after Cao Ren gave up on Xiangyang and Fancheng. Cao Pi regretted not listening to him.

Throughout the course of 220, Sima Yi would go on to serve as one of the leading officials in court to support and urge for Cao Pi's seizure of the throne, joined as he were by a number of other officials.

In late 220, Cao Pi usurped the throne from Emperor Xian, ended the Eastern Han dynasty, and declared himself emperor of the newly established state of Wei. Cao Pi first appointed Sima Yi as a Master of Writing (尚書) but later reassigned him to be an Army Inspector (督軍) and Palace Assistant Imperial Clerk (御史中丞). He also promoted Sima Yi from a village marquis to a district marquis under the title "Marquis of Anguo District" (安國鄉侯).

In 221, Sima Yi was removed from his post as an Army Inspector and was appointed as a Palace Attendant (侍中) and Right Supervisor of the Masters of Writing (尚書右僕射).

In 222, when Cao Pi visited Wancheng (宛城; present-day Wancheng District, Nanyang, Henan), either because the city wasn't celebratory enough, or because a local market had failed to produce a type of medicine Cao Pi had requested, the Governor of Nanyang (南陽太守), Yang Jun (楊俊), under whose authority the city fell, was arrested. Sima Yi, among other officials, was on good terms with Yang Jun, whom he had previously met during his youth and considered capable and intelligent, and therefore pleaded on his behalf; knocking his forehead on the ground until it started bleeding, but Cao Pi dismissed the appeal. Yang Jun, admitting that he was at fault, committed suicide. Sima Yi was greatly saddened at such a loss.

Two years later, in September 224, Cao Pi went on a tour of the south to inspect his forces in the areas near the Wei–Wu border. Sima Yi remained behind to defend Xuchang and his marquis title was changed to "Marquis of Xiang District" (向鄉侯).

In the spring of 225, he was appointed General Who Pacifies the Army (撫軍將軍) and placed in command of 5,000 troops, in addition to holding the positions of Official Who Concurrently Serves in the Palace (給事中) and Manager of the Affairs of the Masters of Writing (錄尚書事). When Sima Yi declined to accept these appointments, Cao Pi told him: "I am so busy with state affairs that I have been working through both day and night and have hardly a moment for rest. (When I entrust you with these responsibilities,) I am not commending you, but rather, I need you to help me share my burden."

In 226, Cao Pi led his armies to attack Sun Quan and left Sima Yi behind to defend and govern the imperial capital in his absence, as well as providing reinforcements and supplies for his armies at the frontline. Before departing, Cao Pi issued a decree: "I am deeply concerned about what happens after I die. This is why I entrust you with this responsibility. Even though Cao Shen made many contributions on the battlefield, Xiao He played a more important role than him. Can I be free of worries I have about the west (referring to the rival state Shu in the west)?" Cao Pi later returned from Guangling Commandery to Luoyang and he told Sima Yi: "When I am in the east, you will be in charge of the west; when I am in the west, you will be in charge of the east." Sima Yi remained behind to guard Xuchang.

In mid 226, when Cao Pi became critically ill, he summoned Sima Yi, Cao Zhen, Chen Qun, and possibly Cao Xiu to meet him in the south hall of Chonghua Palace (崇華殿), where he ordered them to assist his son Cao Rui after his death. Cao Pi also told Cao Rui: "There may be those who would alienate these Three Ducal Ministers from you, but be careful and do not doubt them."

Service under Cao Rui

Driving back Wu invaders

After Cao Rui became the Wei emperor, he elevated Sima Yi from the status of a district marquis to a county marquis under the title "Marquis of Wuyang (County)" (舞陽侯). Around that time, Sun Quan attacked Jiangxia Commandery (江夏郡; around present-day Xinzhou District, Wuhan, Hubei) and sent his generals Zhuge Jin and Zhang Ba (張霸) to attack Xiangyang. Sima Yi led Wei forces to resist the Wu invaders, defeated Zhuge Jin, and killed Zhang Ba and more than 1,000 Wu soldiers. In recognition of Sima Yi's efforts, Cao Rui promoted Sima Yi to General of Agile Cavalry (驃騎將軍).

Suppressing Meng Da's rebellion

A Qing dynasty illustration of Meng Da's death at Xincheng.

In July 227, Cao Rui ordered Sima Yi to garrison at Wancheng (宛城; present-day Wancheng District, Nanyang, Henan) and put him charge of the military affairs of Jing and Yu provinces.

Earlier, during Cao Pi's reign, Sima Yi had warned Cao Pi that Meng Da, a former Shu general who had defected to Wei, was untrustworthy, but Cao Pi ignored him. He was proven right after Cao Pi's death, as towards the end of 227, Sima Yi received news that Meng Da was planning to rebel against Wei and return to Shu, and so, according to the Weilüe, he had sent his adviser Liang Ji (梁幾) to investigate Meng Da's case while urging Meng Da to visit the Wei capital Luoyang to attend to court, which alarmed the latter and finally convinced him to rebel.

The Book of Jin and Zizhi Tongjian, however, are in agreement that Sima Yi, upon hearing that Meng Da wished to rebel, instead wrote a flattering letter to Meng Da to distract and confuse him while preparing to suppress the rebellion. While Meng Da was stuck in a dilemma on whether to commit to his rebellion or not, Sima Yi swiftly assembled his troops and in secret led them to attack Meng Da's base in Shangyong Commandery (上庸郡; around present-day Zhushan County, Hubei). While heading towards the location, Sima Yi's subordinates suggested that they observe Meng Da's actions first before advancing, but Sima Yi replied: "(Meng) Da is not a trustworthy person. Now that he is hesitating due to suspicions, we should seize this opportunity to get rid of him." The marching speed was subsequently hastened and, covering 2,200 li, Sima Yi reached there within eight days and ordered his subordinates to lead separate detachments to intercept and block Meng Da's reinforcements in the form of Shu and Wu forces that had just arrived at An Bridge (安橋) and Mulan Fort (木闌塞) in Xicheng (西城) respectively.

Meng Da was taken by utter surprise as he did not expect Sima Yi to show up at Shangyong Commandery so quickly. As Meng Da was surrounded on three sides by a river, he set up wooden barriers to defend himself. Sima Yi's forces crossed the rivers, destroyed the barriers, and arrived just outside Shangyong. Sima Yi split up his forces and attacked the city from eight different directions for over two weeks. On the sixteenth day, Meng Da's nephew Deng Xian (鄧賢) and subordinate Li Fu (李輔) opened the city gates and surrendered to Sima Yi. Meng Da was captured and executed and his head sent to the capital Luoyang; more than 10,000 captives were taken and Sima Yi returned to Wancheng in triumph.

Governing Jing and Yu provinces

While he was in charge of Jing and Yu provinces, Sima Yi encouraged and promoted agriculture and reduced wastage of public funds. The people of the southern lands were happy and showed their support for him.

Shen Yi, a former subordinate of Meng Da, had remained in Weixing Commandery (魏興郡; around present-day Ankang, Shaanxi) for a long time and had become deeply entrenched there. All these years, he had been illegally using the Wei emperor's name to carve official stamps and seals, and giving them to others. After hearing of Meng Da's downfall, he became worried that he would be the next target of Sima Yi's crackdown on traitorous officials. Around that time, as Sima Yi had just suppressed Meng Da's rebellion, many regional officials came to present gifts and congratulate him. Sima Yi sent a messenger to provoke Shen Yi and lure him into a trap. When Shen Yi came to confront him, he fell into the trap and was captured and sent to the imperial capital. Sima Yi also relocated to You Province more than 7,000 households who used to live in Shangyong Commandery. The Shu military officers Yao Jing (姚靜), Zheng Ta (鄭他), and others later brought more than 7,000 men with them to surrender to Sima Yi. However, these Shu military officers, who are primarily referenced in the Book of Jin, do not appear in the Zizhi Tongjian and Records of the Three Kingdoms and Chronicles of Huayang.

At the time, among the thousands of people who migrated to Wei from Shu, many were unregistered residents, so the Wei government wanted to have them officially registered as citizens of Wei. The Wei emperor, Cao Rui, summoned Sima Yi back to Luoyang and sought his opinion on this issue. Sima Yi said: "The enemy seized these people through deception and now abandon them. It's advisable to have them registered. This way, they will feel happy and at ease." Cao Rui then asked him which of Wei's two rival states (Wu and Shu) they should attack first. Sima Yi replied: "The people of Wu know that we are not adept in naval warfare, hence they dare to live in Dongguan. When we attack an enemy, we should always block its throat and strike its heart. Xiakou and Dongguan are the enemy's heart and throat. If we can move our land forces to Wan to lure Sun Quan to advance east, and take advantage of Xiakou's low defences by sending our navy to attack it, it will be like an army from Heaven descending (upon the enemy) and they will definitely be defeated." Cao Rui agreed with Sima Yi's view and ordered him to return to his post at Wancheng (宛城; present-day Wancheng District, Nanyang, Henan).

Around August 228, during the time of the Battle of Shiting, records make brief mention of Sima Yi's involvement in the events by stating that he led Wei forces into Jiangling (江陵; present-day Jiangling County, Jingzhou, Hubei).

Aborted campaign against Shu

In March 230, Sima Yi was promoted to General-in-Chief (大將軍), appointed Grand Chief Controller (大都督), and given a ceremonial yellow axe. The Wei emperor, Cao Rui, put him and Cao Zhen in charge of defending Wei's western borders from attacks by its rival state Shu, which had been launching invasions since 228. At Cao Zhen's instigation, a campaign against Shu was proposed and eventually implemented after Cao Rui approved his proposal. In September 230, Cao Zhen led an army from Chang'an to attack Shu via the Ziwu Valley (子午谷). At the same time, another Wei army led by Sima Yi, acting on Cao Rui's order, advanced towards Shu from Jing Province by sailing along the Han River. The rendezvous point for Cao Zhen and Sima Yi's armies was at Nanzheng County (南鄭縣; in present-day Hanzhong, Shaanxi). The army led by Sima Yi passed through Zhuoshan (斫山) and Xicheng County (西城縣; present-day Ankang, Shaanxi), sailed along the Mian River to Quren County (朐忍縣; west of present-day Yunyang County, Chongqing), and arrived at Xinfeng County (新豐縣; south of present-day Weinan, Shaanxi). He made camp at Dankou (丹口). Other Wei armies also prepared to attack Shu from the Xie Valley (斜谷) or Wuwei Commandery. However, the campaign eventually had to be aborted by October 230, because the gallery roads leading into Shu were too damaged for the troops to pass through, and also because of constant heavy downpour, which had lasted for more than 30 days.

Battle of Mount Qi

The following year, in 231, Shu forces led by Zhuge Liang attacked Tianshui Commandery and besieged Wei forces led by Jia Si (賈嗣) and Wei Ping (魏平) at Mount Qi (祁山; the mountainous regions around present-day Li County, Gansu). Cao Rui ordered Sima Yi to move to Chang'an (present-day Xi'an, Shaanxi) to supervise military operations in Yong and Liang provinces. Sima Yi then ordered Fei Yao and Dai Ling to protect Shanggui County (上邽縣; in present-day Tianshui, Gansu) with 4,000 elite troops and set out with the rest of his men westward to relieve the mountainous battlefield. Zhang He wanted to take a detachment and station it at Yong (雍) and Mei (郿) counties, but Sima Yi reasoned: "If the vanguard is able to face the enemy alone, your words are right; but should they not be able to do so, the dividing of the forces into vanguard and rear would be unwise; in this manner the Three Armies of Chu were captured by Qing Bu." After making preparations for battle, Sima Yi, with Zhang He, Fei Yao, Dai Ling (戴陵), and Guo Huai serving as his subordinates, led the Wei forces to Yumi County (隃麋縣; east of present-day Qianyang County, Shaanxi) and stationed there.

When Zhuge Liang heard of the Wei army's arrival, he led his troops to Shanggui County to collect the harvest. Supposedly, without good coordination, Sima Yi's subordinates defied his order to defend their positions; a detachment of the Wei army went to attack the Shu forces, but were defeated, although accounts from the Book of Jin make no mention of a detachment being defeated, and records of the campaign in general tend to vary and prove unreliable. After getting the enemy out of the way, Zhuge Liang foraged for the early spring wheat that was available in the vicinity. Sima Yi's subordinates feared losing the wheat, but Sima Yi stated that "Zhuge Liang thinks too much and makes too little decisions. He'll definitely fortify his camp and defences first before coming to harvest the wheat. Two days is sufficient for me (to reach Shanggui County)." He indeed reached there within two days after travelling overnight. When Zhuge Liang and his men heard that Sima Yi was marching towards their position, they swiftly retreated instead of giving battle. Sima Yi commented: "I'm weary from travelling day and night. This is because I know what militarists covet. Zhuge Liang does not dare to remain near the Wei River. This is easy for me." Initially, the Wei emperor, Cao Rui, wanted to supply Sima Yi's army with the wheat in Shanggui County and had rejected a proposal to transport grain from Guanzhong to the frontline. However, Zhuge Liang's movements turned out to be quicker than Cao Rui anticipated; only a portion of the wheat produce in Shanggui County was left after the Shu army's harvesting. The Wei general Guo Huai then asserted his influence over local nomadic tribes and forced them to produce food supplies for the Wei army. The Wei army was thus able to gain access to food supplies without assistance from the central government in Luoyang.

Sima Yi again encountered Zhuge Liang, this time east of Shanggui County, at Hanyang (漢陽), but no direct engagement came of it; Sima Yi drew his troops in and put them into formation while waiting, finding protection in the nearby defiles; concurrently he sent Niu Jin to lead a lightly-armed cavalry detachment to lure the enemy to Mount Qi, who in the process briefly engaged in battle with Shu vanguard commander Ma Dai and managed to inflict some losses on the enemy. Zhuge Liang simultaneously withdrew his forces, and Sima Yi thereafter closely followed Zhuge Liang from the rear. Zhang He reportedly advised against pursuit on grounds that they could effectively station at Mount Qi, combine their forces, and indulge in conducting irregular expeditions, as well as that Zhuge Liang's provisions were running low, effectively having the strategic problem take care of itself, as Zhuge Liang would soon be forced to retreat, but Sima Yi did not heed this advice, and continued his pursuit. Zhuge Liang meanwhile ordered a retreat towards the eastern side of the Mount Qi ridges, where the Shu army fortified at Lucheng (鹵城), seizing control of the hills in the north and south, and using the river as a natural barrier while pitching "covering camps" near the riverbank to take complete control of the water passage.

Although his subordinates repeatedly urged him to attack the enemy, Sima Yi was hesitant to do so after seeing the layout of the Shu camps in the hills. However, he eventually relented when his subordinates criticised and mocked him by saying he would become a laughing stock if he refused to attack. Sima Yi sent Zhang He to attack the southern Shu camps, guarded by Wang Ping, while he personally led a frontal assault on Lucheng from the central avenue. In response, Zhuge Liang ordered Wei Yan, Wu Ban, and Gao Xiang to lead troops to engage and resist the enemy outside Lucheng. The Wei forces suffered an unexpected and tremendous defeat: 3,000 soldiers were killed, and 5,000 suits of armour and 3,100 sets of hornbeam crossbows were seized by the Shu forces; however, Sima Yi still retained a sizable army, which he led back to his camp.

Despite his victory, Zhuge Liang could not make use of the momentum to launch a major offensive on the enemy because his army was running low on supplies. The Book of Jin claimed that Sima Yi launched an attack on the Shu garrisons at this juncture and succeeded in capturing the Shu "covering camps". Zhuge Liang abandoned Lucheng and retreated under the cover of night, but Sima Yi pursued him and inflicted roughly 10,000 casualties on the Shu army. This account from the Book of Jin is disputed by historians and is not included in the Zizhi Tongjian. According to the Records of the Three Kingdoms and Zizhi Tongjian, Zhuge Liang supposedly retreated due to a lack of supplies, not due to defeat, and the Wei forces pursued him. The pursuit itself did not go completely smoothly for Wei. Sima Yi had ordered Zhang He to further pursue the enemy in an attempt to capitalise on their momentum. The Weilüe mentioned that Zhang He apparently refused to initially obey Sima Yi's order and argued that, according to classical military doctrine, one should refrain from pursuing an enemy force retreating to its home territory. However, Sima Yi refused to listen and forced Zhang He to carry out this order. Zhang He fell into an ambush at Mumen Trail (木門道; near present-day Mumen Village, Mudan Town, Qinzhou District, Tianshui, Gansu), where Zhuge Liang had ordered crossbowmen to hide on high ground and fire at approaching enemy forces when they entered a narrow defile; Zhang He died after a stray arrow hit him in the right knee. Regardless of this setback, Cao Rui sent an emissary to congratulate Sima Yi on his victory and rewarded him by adding more taxable households to his marquisate.

Du Xi, who was his adviser, and Xue Ti (薛悌) told Sima Yi that the wheat will be ready for harvest the following year and Zhuge Liang would definitely come to seize the wheat. Since Longyou (隴右) lacked food supplies, they should transport the wheat there that winter. Sima Yi said: "Zhuge Liang advanced towards Mount Qi again and attacked Chencang (陳倉; east of present-day Baoji, Shaanxi) but lost and withdrew. If he advances again, instead of attacking cities, he will call for a battle in the east of Long(you) and not the west. Zhuge Liang feels frustrated by the shortage of grain so he will definitely stockpile supplies when he returns (to Shu). Based on my prediction, he won't attack again if he doesn't have at least three harvests' worth of food supplies." Sima Yi then proposed to the Wei imperial court to mobilise farmers from Ji Province to Shanggui County and put them under the jurisdiction of Jingzhao (京兆), Tianshui, and Nan'an (南安) commanderies. By 233, Sima Yi's agricultural plan came to fruition and became a source of food supplies for the three commanderies.

Battle of Wuzhang Plains

A Qing dynasty illustration of "a dead Zhuge drives away a living Zhongda".

In March or April 234, Zhuge Liang reportedly led around 100,000 Shu troops (although it was likely closer to 60,000) out of the Xie Valley (斜谷) and camped at the southern bank of the Wei River near Mei County (郿縣; southeast of present-day Fufeng County, Shaanxi).

Sima Yi's subordinates wanted to station their camp north of the Wei River, but Sima Yi said: "Many civilians have gathered at the south of the Wei River. That will definitely become a hotly contested location." Sima Yi then led his troops across the Wei River and took up his position with his rear facing the river, and began constructing fortifications. He additionally said: "If Zhuge Liang is brave enough, he'll move out from Wugong County (武功縣; east of present-day Mei County, Shaanxi) and head eastward in the direction of the mountains. If he moves west to the Wuzhang Plains, we'll have no worries." Around that time, the Wei emperor, Cao Rui, became worried, and so decided to send the general Qin Lang to lead 20,000 infantry and cavalry as reinforcements to join Sima Yi.

While Sima Yi and his troops were stationed at the south of the Wei River, Guo Huai urged him and the various officers to move a detachment to the plains on the north bank of the river as he foresaw that Zhuge Liang would attempt to seize the plains. When the other officers disagreed, Guo Huai stated: "If Zhuge Liang crosses the Wei River and occupies those plains, his troops will have access to the mountains in the north. If they block the road through the mountains, it will cause fear and panic among the people living in the region. This isn't helpful to our state." Sima Yi finally agreed with Guo Huai and sent him to occupy the plains. While Guo Huai and his men were building a camp on the plains, they came under attack by Shu forces, but managed to drive them back.

During that time, Zhuge Liang moved his army west to the Wuzhang Plains and prepared to cross to the northern bank of the Wei River. Sima Yi sent Zhou Dang (周當) to station at Yangsui (陽遂; the area north of the Wei River in present-day Mei and Fufeng counties, Shaanxi) and lure Zhuge Liang to attack him. However, Zhuge Liang did not mobilise his troops for several days, and Sima Yi reportedly exclaimed: "Zhuge Liang wants to take control of the Wuzhang Plains and won't advance towards Yangsui. His intention is obvious." He then sent Hu Zun (胡遵) and Guo Huai to defend Yangsui. Several days later, Guo Huai received news that Zhuge Liang was planning to launch an attack in the west, and his subordinates therefore wanted to strengthen their defences in the west. Guo Huai was the only one who recognised that it was a ruse, and that Zhuge Liang was actually planning to attack Yangsui. He was proven right later as the Shu forces attacked Yangsui at night. However, as Guo Huai had set up defences earlier, the Shu forces failed to capture Yangsui. Zhuge Liang could not advance further, so he retreated back to the Wuzhang Plains.

One night, Sima Yi saw a star falling towards the Shu camp and predicted that Zhuge Liang would be defeated. He ordered a surprise attack on the Shu camp from behind: 500 Shu soldiers were killed, 600 surrendered, and more than 1,000 livestock of the Shu army were captured by Wei forces. This account, which stems from the Book of Jin, is not included in the Zizhi Tongjian. Instead, the accounts from the Records of the Three Kingdoms were included in the Zizhi Tongjian.

Around that time, the Wei government observed that since the Shu army was far away from its base at Hanzhong Commandery, it would not be in its interest to fight a prolonged war in enemy territory, so it would be better for the Wei army to adopt a defensive posture against the Shu invaders. The Wei emperor, Cao Rui, thus ordered Sima Yi to hold his position and refrain from engaging the Shu forces in battle. Zhuge Liang attempted to lure Sima Yi to attack him; on one occasion, Zhuge Liang supposedly sent Sima Yi women's ornaments to taunt him. Sima Yi, apparently feeling enraged, sought permission from Cao Rui to attack the enemy, but was denied. The emperor even sent Xin Pi, bearing the imperial sceptre (a symbol of the emperor's authority), to the battlefield to make sure that Sima Yi followed orders and remained in camp. Zhuge Liang knew that Sima Yi was pretending to be angry because he wanted to show the Wei soldiers that he would not put up with the enemy's taunting, and to ensure that the Wei soldiers were ready for battle.

According to the Book of Jin, when Sima Fu wrote to Sima Yi to ask him about the situation at the Wuzhang Plains, Sima Yi replied by saying: "Zhuge Liang has big ambitions but he fails to recognise opportunities. He is full of wits but not decisive. He likes leading troops into battle even though he does not have much authority over them. Even though he has 100,000 troops under his command, he has already fallen into my trap and I'll certainly defeat him." When Zhuge Liang's envoy visited Sima Yi's camp, the latter allegedly inquired about his sleeping and eating habits, along with how busy he was. When told how Zhuge Liang consumed little and didn't sleep much, Sima Yi said to his men: "Zhuge Kongming takes little food and does much work; how can he last long?"

Meanwhile, according to at least one source, Sima Yi continued to provoke Zhuge Liang. Sima Yi reportedly made some 2,000 people cheer by the southeast corner of the military compound. When Zhuge Liang sent a man to inquire on the situation, he stated: "Eastern Wu's envoy came and said he would surrender." Zhuge Liang responded: "Eastern Wu will not surrender. Sima Yi is an old man who will soon be 60 years old, does he really need to use such a trick?"

After a standoff lasting more than 100 days, Sima Yi heard from civilians that Zhuge Liang had died from illness and the Shu army had burnt down their camp and retreated. He then led his troops to pursue the enemy and caught up with them, but withdrew when the Shu forces got into battle formation. Some days later, Sima Yi surveyed the remains of the Shu camp and thereafter reportedly exclaimed: "He was a genius." He also concluded that Zhuge Liang was indeed dead when he saw that the Shu army had hastily retreated. Xin Pi felt that they could not be certain about Zhuge Liang's death yet, but Sima Yi said: "The most important things in an army are its documents, troops, horses, and supplies. (Zhuge Liang) has abandoned all of them. How can a person lose his five most important organs and still be alive? We should quickly pursue (the enemy)." The ground in the Guanzhong region was full of devil's weed so Sima Yi sent 2,000 men wearing wooden clogs with flat soles to clear the path before his main army advanced and continued pursuing the enemy, although he retreated when he eventually encountered the Shu forces. When Sima Yi reached Chi'an (赤岸), he asked the civilians living there about Zhuge Liang and heard that there was a saying: "A dead Zhuge (Liang) scares away a living Zhongda." When Sima Yi heard that, he laughed and said: "I can predict the thoughts of the living but I can't predict the dead's."

In 235, Sima Yi was promoted to Grand Commandant (太尉) and had the number of taxable households in his marquisate increased. In the same year, when the Shu general Ma Dai led troops to invade Wei, Sima Yi sent Niu Jin to lead Wei forces to resist the invaders. Niu Jin defeated Ma Dai and killed more than 1,000 enemy soldiers. However, this account from the Book of Jin is not referenced in the Zizhi Tongjian. When a famine broke out in Guandong (關東; referring to the area east of Hangu Pass), Sima Yi had more than five million hu of grain transported from Chang'an to Luoyang to aid in disaster relief efforts.

Around this time, Sima Yi established a military market at Chang'an. When an official named Yan Fei (顏斐) reported that the soldiers were insulting the people living there, he summoned the market captain and personally flogged him 100 times in front of Yan Fei, and thereafter strictly supervised the conduct of all the officials and soldiers.

Liaodong campaign

Gongsun-controlled territory (light green, approximate).

In 236, Sima Yi caught a white deer, which was regarded as an auspicious animal, and presented it to the Wei emperor, Cao Rui. Cao Rui said: "When the Duke of Zhou assisted King Cheng in governance, he presented white pheasants to the king. Now you are in charge of Shaanxi and you present a white deer. Isn't this a sign of loyalty, cooperation, long-lasting stability, and peace?" Later, when Cao Rui asked for capable and virtuous men to be recommended to him, Sima Yi chose to recommend Wang Chang.

Around that time, Gongsun Yuan, a warlord based in Liaodong Commandery (in present-day Liaoning) who previously pledged allegiance to the Wei state, started a rebellion and declared independence, defeating the general Guanqiu Jian in an engagement.

In January 238, Cao Rui summoned Sima Yi back to the imperial capital Luoyang to lead a campaign against Liaodong. When asked by the emperor as to how Gongsun Yuan will respond, Sima Yi stated that there were three choices available: to flee, to resist, and to defend his capital city, with the last being the worst choice, and the one he was most likely going to employ against Sima Yi after putting up some initial resistance. When further asked by the emperor on how long it will take, Sima Yi said that he needed only one year in total to lead the troops to Liaodong, to suppress the revolt, and to then return and repose. At the time, the Wei government had forced many men into military service or recruited them for manual labour to work on Cao Rui's palace construction/renovation projects. Sima Yi felt that doing so would increase the burden on the common people and make them resent the Wei government, so he advised Cao Rui to halt the projects and focus on dealing with the more pressing issues.

Thereafter, Sima Yi set out with an army of 40,000 men from Luoyang to attack Liaodong, with Niu Jin and Hu Zun (胡遵) serving as his subordinates. Cao Rui personally saw him off at Luoyang's Ximing Gate (西明門), where he ordered Sima Yi's brother Sima Fu and son Sima Shi, as well as other officials to attend the ceremony. During the extensive and lively festivities, in which Sima Yi met with elders and old friends, he began sighing and, feeling emotional and dissatisfied, sang a song:

Heaven and Earth unfold and open up, (the) Sun and Moon are very bright.

Coming to a border meeting, a final effort in distant lands.

(I am) about to seep away the dirty pack, returning to pass by the old hometown.

Respectful and pure for ten thousand li, all equally in every direction.

Announcing success and returning in old age, awaits not in Wuyang. [Wuyang was his fief]

Thereupon he finally advanced with the army, which would later be reinforced by Guanqiu Jian's own forces in You Province, which included the Xianbei auxiliary led by Mohuba (莫護跋), ancestor of the Murong clan. The Wei army reached Liaodong in June 238, and as Sima Yi had anticipated, Gongsun Yuan had sent his Grand General Bei Yan (卑衍) and Yang Zuo (楊祚) to face him. They built their camps along the Liao River in anticipation of him. The Wei generals wanted to directly attack the enemy on the banks of the river, but Sima Yi reasoned that attacking the encampment would only wear themselves out and deplete their valuable resources; on the other hand, since the bulk of the Liaodong army was at the Liao River, Gongsun Yuan's headquarters at Xiangping (襄平; present-day Liaoyang), the capital of the Liaodong Commandery, would be comparatively empty and the Wei army could take it with ease. Sima Yi therefore decided to dispatch Hu Zun with a contingent of his army south with numerous banners and drums, so as to indicate that he was going to make a sortie there with a large force. This deceived Bei Yan and his men, who pursued the decoy unit, whereby Hu Zun, having lured the enemy out, crossed the river and broke through Bei Yan's line, while Sima Yi managed to secretly cross the river to the north, sink the boats, burn down the bridges, build up a long barricade along the river, and then march for the capital itself. Once the opposing generals realised they had fallen for a feint, they started marching back in haste towards the capital, and in the night while heading north to intercept Sima Yi, as had been expected of them, they caught up at Mount Shou (首山; a mountain west of Xiangping), where Bei Yan was ordered to give battle, and was subsequently routed and crushed by Sima Yi and his army. Sima Yi then marched towards Xiangping unopposed, and started besieging it.

Along with the month of July came the summer monsoons, which had impeded Guanqiu Jian's campaign a year ago. There was a constant heavy downpour for more than a month, so that even ships could sail the length of the flooded Liao River from its mouth at the Liaodong Bay up to the walls of Xiangping. Despite the water being several feet high on level ground, Sima Yi was determined to maintain the siege regardless of the clamours of his officers who proposed changing camps; threatening to execute those who advocated for the idea, such as one of the officers, Zhang Jing, who violated the order. The rest of the officers subsequently became silent.

Because of the floods, the encirclement of Xiangping was by no means complete, and the defenders used the flood to their advantage to sail out to forage and pasture their animals. Sima Yi forbade his generals from pursuing the foragers and herders from Xiangping, and upon being questioned by one of his subordinates, stated: "Meng Da's multitudes were small, but he had food and supplies for a year. My generals and soldiers were four times those of Da, but with provisions not even for a full month. Using one month to plot against one year, how could I not be quick? To use four to strike against one, if it merely makes half be eliminated, I would still do it. In this case, I consider not calculations on death and injuries, I compete against provisions. Now, the rebels are numerous and we are few; the rebels are hungry and we are full. With flood and rain like this, we cannot employ our effort. Even if we take them, what is the use? Since I left the capital, I have not worried about the rebels attacking us, but have been afraid they might flee. Now, the rebels are almost at their extremity as regards supplies, and our encirclement of them is not yet complete. By plundering their cattle and horses or capturing their fuel-gatherers, we will be only compelling them to flee. War is an art of deception; we must be good at adapting ourselves to changing situations. Relying on their numerical superiority and helped by the rain, the rebels, hungry and distressed as they are, are not willing to give up. We must make a show of inability to put them at ease; to alarm them by taking petty advantages is not the plan at all."

The officials back in the Wei imperial court in Luoyang were also concerned about the floods and proposed recalling Sima Yi. The Wei emperor, Cao Rui, being completely certain in Sima Yi's abilities, turned the proposal down. Around this time, the Goguryeo king sent a noble (大加; taeka) and the Keeper of Records (主簿; jubu) of the Goguryeo court with several thousand men to aid Sima Yi.

On 3 September, a comet was seen in the skies of Xiangping and was interpreted as an omen of destruction by those in the Liaodong camp. A frightened Gongsun Yuan sent his Chancellor of State Wang Jian (王建) and Imperial Counsellor Liu Fu (柳甫) to negotiate the terms of surrender, where he promised to present himself bound to Sima Yi once the siege was lifted. Sima Yi, wary of Gongsun Yuan's double-crossing past, executed the two, explaining his actions in a message to Gongsun Yuan that he desired nothing less than an unconditional surrender: "In ancient times, Chu and Zheng were classed as states of equal footing, yet the Earl of Zheng nevertheless met the Prince of Chu with his flesh bare and leading a sheep. I am a superior Ducal Minister of the Son of Heaven, yet Wang Jian and his following wanted me to raise the siege and withdraw my men. Is this proper? These two men were dotards who must have failed to convey your intentions; I have already put them to death (on your behalf). If you still have anything to say, then send a younger man of intelligence and precision."

When Gongsun Yuan sent Wei Yan (衛演) for another round of talks, this time requesting he be allowed to send a hostage to the Wei court, Sima Yi dismissed the final messenger as a waste of time: "In military affairs there are five essential points. If able to fight, you must fight. If not able to fight, you must defend. If not able to defend, you must flee. The remaining two points entail only surrender or death. Now that you are not willing to come bound, you are determined to have death; there is no need of sending any hostage." Apparently, Sima Yi's previous suggestion of further negotiations was nothing more than an act of malice that gave false hope to Gongsun Yuan while prolonging the siege and placing further strain on the supplies within the city.

When the rain stopped and the floodwater got drained away, Sima Yi hastened to complete the encirclement of Xiangping. The siege carried on day and night, which utilised mining, hooked ladders, battering rams, and artificial mounds for siege towers and catapults to get higher vantage points. The speed at which the siege was tightened caught the defenders off guard: since they had been obtaining supplies with such ease during the flood, there apparently was not any real attempt made to stockpile the goods inside Xiangping, and as a result, famine and cannibalism broke out in the city. Many Liaodong generals, such as Yang Zuo, surrendered to Sima Yi during the siege.

On 29 September, the famished Xiangping fell to the Wei army. Gongsun Yuan and his son Gongsun Xiu (公孫脩), leading a few hundred horsemen, broke out of the encirclement and fled to the southeast. The main Wei army gave pursuit and killed both father and son on the Liang River (梁水; present-day Taizi River). Gongsun Yuan's head was cut off and sent to Luoyang for public display. A separate fleet led by future Grand Administrators Liu Xin (劉昕) and Xianyu Si (鮮于嗣) had been sent to attack the Korean commanderies of Lelang and Daifang by sea, and in time, all of Gongsun Yuan's former holdings were subjugated.

After his army occupied Xiangping, Sima Yi erected a pair of guideposts to separate recent and long-time serving government officials and military personnel of Gongsun Yuan's disestablished regime, and thereafter ordered a systematic purge of some 2,000 officials. He also had some 7,000 men aged 15 and above from within the city executed and raised a victory mound (京觀) with their corpses, while pardoning all the remaining survivors. In total, Sima Yi's conquest gained Wei an additional 40,000 households and over 300,000 citizens, although Sima Yi did not encourage these frontier settlers to continue their livelihoods in the Chinese northeast and instead ordered that those families who wished to return to central China be allowed to do so. Sima Yi also posthumously rehabilitated and erected mounds over the graves of Lun Zhi (倫直) and Jia Fan (賈範), two officials who had attempted to stop Gongsun Yuan from rebelling but were executed by him, and also freed Gongsun Gong, the previous Administrator of Liaodong, who had been imprisoned by his nephew Gongsun Yuan, with all of this being carried out under an order which stated: "During the ancients' attacks on states, they executed their fiercest enemies [literally: "whales" (鯨鯢)], and that was all. Those who were deceived and misled by Wenyi, all are forgiven. People of the Central States who desire to return to their old hometowns are free to do so."

At the time, as it was winter, many soldiers were suffering from the cold and wanted extra clothing to keep themselves warm. When someone pointed out that they had a surplus of ru (襦; a type of short coat) and suggested giving them out to the soldiers, Sima Yi said: "The padded coats are the property of the government. No one is allowed to give them to others without permission." Sima Yi did, however, memorialise that all soldiers aged 60 and above, numbering over 1,000 men, to retire from their service, and for the dead and wounded to be sent home. As Sima Yi led the troops back to Luoyang from Liaodong, Cao Rui sent an emissary to meet them in Ji County (薊縣; in present-day Beijing) and host a party to celebrate the victory. He also added Kunyang County (昆陽縣; present-day Ye County, Henan) to Sima Yi's marquisate, so Sima Yi had a total of two counties as his marquisate.

Appointment as regent

When Sima Yi arrived at Xiangping, he allegedly dreamt that Cao Rui requested him to look at his face, and upon witnessing it, saw that it appeared different than usual, and Sima Yi sensed that something was wrong. Later, when Sima Yi was in Ji County (汲縣; in present-day Xinxiang, Henan), Cao Rui issued an imperial order instructing him to return to Luoyang via a faster route through the Guanzhong region. When Sima Yi reached Baiwu (白屋), he received another five orders within three days. Sensing the urgency of the situation, he boarded a zhuifengche (追鋒車) and travelled overnight across the Baiwu region over a distance of more than 400 li, while stopping only once for a brief moment of rest, and reached Luoyang by the following day. Upon arrival, he was led to the bedroom of the Jiafu Hall (嘉福殿) in the imperial palace to meet Cao Rui and saw that the emperor was critically ill. With tears in his eyes, Sima Yi asked Cao Rui about his condition. Cao Rui held Sima Yi's hand and told him: "I have matters to entrust you. Now that I meet you one last time before I die, I have no more regrets." Cao Rui called into his chambers the Prince of Qin, Cao Xun, and the Prince of Qi, Cao Fang, and while pointing towards Cao Fang stated: "This is he. Look at him carefully and do not make any mistake." Cao Rui had Cao Fang subsequently embrace Sima Yi's neck. Sima Yi hit his forehead on the floor and started weeping. Cao Rui thereafter designated Sima Yi as a regent for the young Cao Fang, along with another co-regent, the general Cao Shuang, who himself had already been designated for the position at a prior date.

Before his death, Cao Rui had initially planned to exclude Sima Yi from the regency and instead appoint Cao Yu, Xiahou Xian (夏侯獻), Cao Shuang, Cao Zhao, and Qin Lang as the regents. However, two of his close aides, Liu Fang (劉放) and Sun Zi (孫資), who were not on good terms with Xiahou Xian and Cao Zhao, managed to persuade him to not just exclude those two, but Qin Lang and Cao Yu as well, thereby simply having Cao Shuang and Sima Yi appointed as the regents instead.

Service under Cao Fang

In early 239, when Cao Fang started ruling as the new Wei emperor, the Wei government appointed Sima Yi as a Palace Attendant (侍中) and Manager of the Affairs of the Masters of Writing (錄尚書事), granted him imperial authority, and ordered him to oversee military affairs within and outside the imperial capital Luoyang. Sima Yi and Cao Shuang each held command over 3,000 troops and served as regents for the underage emperor. As Cao Shuang wanted the Masters of Writing (i.e. the Imperial Secretariat) to report to him first, he proposed to the imperial court to reassign Sima Yi to be the Grand Marshal (大司馬). As the persons who previously held the position of Grand Marshal all died in office, the imperial court thought that it would be more appropriate to appoint Sima Yi as Grand Tutor (太傅) instead. Sima Yi was also awarded additional privileges similar to those granted to Xiao He in the early Western Han dynasty and Cao Cao in the late Eastern Han dynasty: He did not have to walk briskly when he entered the imperial court, did not have to have his name announced when he entered, and was allowed to wear shoes and carry a sword into the imperial court. His eldest son, Sima Shi, was appointed as a Regular Mounted Attendant (散騎常侍), while three of his relatives were enfeoffed as marquises and four others were appointed as Cavalry Commandants (騎都尉). Sima Yi ordered his relatives to decline the honours and appointments.

In the spring of 239, the Wa, Karasahr, Weixu (危須) states and the Xianbei tribes living south of the Ruo River came to pay tribute to the Cao Wei state. Cao Fang attributed this to the efforts of his subjects and he rewarded Sima Yi by increasing the number of taxable households in his marquisate. Sima Yi also suggested that the Wei imperial court put an end to the extravagant palace construction/renovation projects started in Cao Rui's reign, and divert those resources and manpower towards agriculture instead. The imperial court approved.

Battles in Jing Province

Around late May or June 241, Wei's rival state Eastern Wu launched an invasion of Wei on three fronts: Quebei (芍陂; south of present-day Shou County, Anhui), Fancheng (樊城; present-day Fancheng District, Xiangyang, Hubei), and Zhazhong (柤中; west of present-day Nanzhang County, Hubei). When Sima Yi requested to lead troops to resist the enemy, there were other officials in the imperial court who argued that there was no need to take swift action since Fancheng was strong enough to withstand attacks and that the enemy was weary after travelling a long distance. Sima Yi disagreed and pointed out: "In Zizhong the Chinese people and the barbarians number a hundred thousand; south of the water they wander and roam without a master over them. Fancheng has been under attack more than a month without relief. This is a precarious situation. I ask to lead a campaign myself."

In late June or July 241, Sima Yi led an army from Luoyang to fight the Wu invaders. The Wei emperor, Cao Fang, personally saw him off at Luoyang's Jinyang Gate (津陽門). Upon reaching Fancheng, Sima Yi knew that he should not linger for too long because of the heat of summer. He first sent a lightly-armed cavalry detachment to harass the Wu forces while his main army remained in position. Later, he ordered his tired troops to rest and bathe, while a remaining group of hand-picked forces and enlisted volunteers were ordered to climb up Fancheng's city walls in order to reinforce the city and curb the enemy's siege. The Wu forces, led by Zhu Ran, retreated overnight upon hearing of this. Sima Yi and the Wei forces pursued the retreating Wu forces to the intersection of the Han, Bai, and Tang rivers, where they defeated and killed over 10,000 enemy soldiers and captured their boats, equipment, and other resources. Cao Fang sent a Palace Attendant as an emissary to meet Sima Yi at Wancheng (宛城; present-day Wancheng District, Nanyang, Henan) to congratulate him and host a banquet to celebrate the victory.

In August 241, the Wei imperial court added Yan (郾) and Linying (臨潁) counties to Sima Yi's marquisate as a reward for his contributions; at the time, Sima Yi's marquisate spanned four counties and covered 10,000 taxable households. 11 of Sima Yi's relatives were also enfeoffed as marquises. As Sima Yi gained greater glory for his achievements, he behaved in a more humble and modest manner. For example, whenever he met Chang Lin (常林), who was from the same hometown as him and held the position of Minister of Ceremonies in the Wei imperial court, he bowed to him in a respectful manner. He also constantly reminded his siblings, children, and younger relatives to be mindful of their conduct. In the spring of 242, Cao Fang bestowed the posthumous title "Marquis Cheng of Wuyang" (舞陽成侯) upon Sima Yi's deceased father, Sima Fang.

Promoting agriculture in the Huai River region

The Book of Jin recounts that in April or May 242 Sima Yi proposed to the Wei government to dig a canal to connect the Yellow and Bian rivers and direct their waters towards the southeast to promote agriculture in the areas north of the Huai River.

In an alternative account from the Zizhi Tongjian that instead places this event as having occurred somewhere in the year of 241, it was Sima Yi who was proposed the idea of building such a canal by Deng Ai, for which he only thereafter petitioned the state for. The agricultural project was set in motion and eventually completed, and whenever there was a battle in the southeast between the Wei and Wu armies, the Wei troops could rush downstream toward the Huai River area to counter the enemy. The abundance of food resources and waterways in the upper stream were advantageous for the Wei forces.

Around that time, Zhuge Ke, a general from Wei's rival state Wu, was stationed at a military garrison at Wan (皖; present-day Qianshan County, Anhui) and posed a threat to the Wei forces in the region. When Sima Yi wanted to lead troops to attack Zhuge Ke, many officials advised him against it. They said that Wan was heavily fortified and abundant in supplies and that Wu reinforcements would come to Zhuge Ke's aid if he came under attack, thus putting the invaders in a perilous position. Sima Yi disagreed and said: "The enemy is adept at naval warfare. Why don't we try attacking their land garrison and see what happens. If they know their strengths, they will abandon the garrison and retreat; this is our objective. If they hold up inside the garrison and defend their position, their reinforcements will have to reach them via land because the waters are too shallow in winter for boats to sail through. In doing so, they will be putting themselves at a disadvantage because they aren't as good in land-based warfare as us."

In October 243, Sima Yi led an army from Luoyang to attack Zhuge Ke at Wan. When Sima Yi and his army reached Shu County (舒縣; present-day Shucheng County, Anhui), Zhuge Ke, upon being instructed by Sun Quan to not give battle and instead station at Chaisang (柴桑), gave orders to burn down all the supplies stockpiled in Wan, abandon the garrison, and retreat.

Sima Yi's aim was to destroy the Wu forces' sources of food supply in the Huai River region, so once Zhuge Ke burnt down all the supplies in Wan, Sima Yi felt more at ease. He then implemented the tuntian policy and large-scale agricultural and irrigation works in the region. In late January or February 244, Cao Fang sent an emissary to meet Sima Yi at Huainan Commandery (淮南郡; around present-day Shou County, Anhui) and honour him for his achievements in promoting agriculture in the region.

Power struggle with Cao Shuang

Already throughout the early years of Cao Shuang and Sima Yi's co-regency, the former attempted to consolidate his influence on the political scene, while only initially for a brief amount of time paying some respect to Sima Yi based on his status and seniority. He put his brothers in command of the military, promoted his close aides to higher positions in the imperial court, and made changes to the political structure to benefit himself and his clique. He further silenced those who stood against him, his associates, and their combined interests.

During the same chain of events, Cao Shuang had Sima Yi appointed to the position of Grand Tutor under the guise of a promotion, and while the position was indeed an honourable one, it practically held no actual authority, and removed Sima Yi from the position of Intendant of the Affairs of the Masters of Writing, instead giving authority over the Masters of Writing to Cao Shuang. However, through the careful appointing of some of Sima Yi's aides to certain positions, he managed to effectively retain much of his political influence, and Cao Shuang's attempts at strengthening his grip on the political scene were soon to be at least somewhat mitigated. For instance, Deng Ai, a man with whom Sima Yi had previously grown acquainted and, realising his talent, transferred him into his service, was eventually appointed to the position of Prefect of the Masters of Writing (尚書郎) sometime in 241, allowing Sima Yi to still be able to supervise the edicts and memorials, and after the death of Man Chong in 242, one of Sima Yi's old associates, Jiang Ji, was appointed to the position of Grand Commandant (太尉).

Meanwhile, throughout the course of the 240s, as new groups of intellectuals, largely headed by He Yan, an associate of Cao Shuang, were seeking to oppose traditional Confucian principles and do away with "pointless" formalities in society, Sima Yi became a leading representative of men from good families who sought to promote the traditional type of Confucian morality and restraint in both politics and society as a whole.

In 244, the officials Deng Yang and Li Sheng advised Cao Shuang to launch a military campaign against Wei's rival state Shu to boost his fame and authority in Wei. Sima Yi strongly objected to this idea, but Cao Shuang ignored him and proceeded with the campaign. He suffered a defeat at the Battle of Xingshi in April 244 against Shu forces. Sima Yi sent a letter to Xiahou Xuan reprimanding their reckless actions as they could lead to utter destruction, referring to historical precedent by stating how Cao Cao previously almost suffered a total defeat in the struggle against Liu Bei for Hanzhong, and also mentioning the fact that the Shu forces were already occupying Mount Xingshi (興勢山; situated north of present-day Yang County, Shaanxi), and, if they personally fail to seize control of the area, could end up having their retreat route cut off and their forces destroyed. Xiahou Xuan subsequently grew anxious and advised Cao Shuang to lead his troops back, which he eventually resorted to by June or July of the same year, further incurring losses during his retreat.

In September 245, Cao Shuang wanted to make changes to the structure of the military so that he could put his brothers Cao Xi (曹羲) and Cao Xun (曹訓) in command of troops. Sima Yi opposed these changes, but Cao Shuang ignored him and went ahead. In January 246, the Wei emperor, Cao Fang, granted Sima Yi the privilege of riding to the imperial court in a type of horse-drawn carriage traditionally reserved for emperors.

In February 246, when Eastern Wu forces attacked Zhazhong (柤中; west of present-day Nanzhang County, Hubei), over 10,000 households living in the area fled to the north across the Mian River (沔水). When news of the Wu invasion reached the Wei imperial court, Sima Yi argued that they should let the civilians remain on the north side of the Mian River since the south side was near enemy territory and hence too dangerous for them. However, Cao Shuang said: "It isn't in our long-term interests to allow the civilians to remain here and give up trying to secure the south of the Mian River." Sima Yi disagreed: "If the enemy sends 20,000 troops to cut off passage across the Mian River, sends another 30,000 troops to fight our forces at the south of the Mian River, and sends another 10,000 troops to occupy Zhazhong, what can we do to save those civilians?" Cao Shuang refused and ordered the refugees to return to the south of the Mian River. As Sima Yi foresaw, the Wu forces occupied Zhazhong, captured the civilians, and relocated them to Wu territory.

Around late May or early June 247, Cao Shuang wanted to further dominate the Wei government, so he used a series of political manoeuvres to consolidate and concentrate power in the hands of himself and his clique. He heeded the advice of his close aides He Yan, Deng Yang, and Ding Mi (丁謐), and relocated Empress Dowager Guo (Cao Rui's widow) to Yongning Palace (永寧宮) so that she could not interfere in politics. Sima Yi was unable to stop this, among other contrivances, pushing the relationship between him and Cao Shuang to a breaking point. Cao Shuang himself became increasingly distrustful and wary of Sima Yi. At the time, there was a saying in Luoyang which went: "He (Yan), Deng (Yang) and Ding (Mi) create turmoil in the imperial capital."

In June or July 247, Sima Yi claimed that he was ill and withdrew from the political scene.

The Princes of Qinghe and Pingyuan had been arguing over a land dispute for the past eight years, with Sun Li, the governor of Ji Province, after consulting with Sima Yi, arguing that a map from the Palace Archives made during the time of the latter prince's enfeoffment should be used, which would favour Pingyuan's claim, but Cao Shuang preferred the plaint of the Prince of Qinghe, and so dismissed the appeal. Sun Li sent a memorial in a forceful tone, and Cao Shuang, in anger, banished him from his position for five years. However, he was eventually reinstated as the governor of Bing Province, and visited Sima Yi before taking his leave. Sima Yi saw that something was amiss, and he asked him if he thought it a small thing to be made the governor of Bing Province, or if he instead felt regret for having got himself involved in this whole affair. Sun Li, in tears, said that he didn't take official ranks or past affairs to heart, but that he was worried about the dynasty's future. Sima Yi replied: "Stop for the time being, and bear the unbearable."

In April or May 248, Zhang Dang (張當), a palace eunuch, illegally transferred 11 women out of the imperial harem and presented them to Cao Shuang to be his concubines. Cao Shuang and his close aides thought that Sima Yi was seriously ill and could no longer do anything, so they plotted with Zhang Dang to overthrow the emperor, Cao Fang, and put Cao Shuang on the throne. However, they were still wary of Sima Yi and did not lower their guard against him.

Towards the end of 248, Sima Yi began plotting against Cao Shuang, together with his eldest son, Sima Shi, and with possibly his second eldest son, Sima Zhao, being involved.

Meeting with Li Sheng

At the time, Li Sheng, one of Cao Shuang's supporters, had been recently reassigned to be the Inspector of Jing Province. Cao Shuang secretly instructed him to check if Sima Yi was as ill as he claimed, so Li Sheng visited Sima Yi before leaving for Jing Province. Sima Yi knew the true purpose of Li Sheng's visit, so he pretended to be frail and senile. Li Sheng saw that Sima Yi could not move around and wear clothes without help from his servants, and could not even consume congee without soiling his clothes. He then told Sima Yi: "Everyone thought that your illness was a minor one; alas, who expected you to be in such poor health?" Sima Yi pretended to cough and pant as he replied: "I am old and sick and I am going to die soon. When you go to Bing Province, you should be careful because it is near barbarian territory. We might not see each other again, so I entrust my sons Shi and Zhao to your care." Li Sheng corrected him: "I am returning to my home province, not Bing Province." Sima Yi pretended to mishear and continued saying: "You are going to Bing Province, aren't you?" Li Sheng corrected him again: "My home province is Jing Province." Sima Yi replied: "I am so old and weak that I can't even hear you properly. So now you are going back to your home province. It's time for you to make some glorious achievements!" Li Sheng returned to Cao Shuang and told him: "Sima Yi is dying soon and no longer of sound mind. There's nothing for you to worry about." Later, he said: "It's sad to see that the Grand Tutor is no longer in a good state of health to serve." Cao Shuang lowered his guard against Sima Yi.

Incident at Gaoping Tombs

The Book of Jin asserts that on the night of 4 February, the day before the planned coup, Sima Yi sent spies to monitor the behaviour of his two eldest children. Some hours later, in the early morning, the spies reported to Sima Yi that Sima Shi went to bed as usual and slept peacefully, whereas Sima Zhao, having allegedly only been informed of the plan during the prior evening, tossed and turned in his bed.

On 5 February 249, Cao Shuang and his brothers accompanied the emperor, Cao Fang, on a visit to the Gaoping Tombs (高平陵) to pay their respects to the late emperor, Cao Rui. On that day, Sima Yi seized the opportunity to stage a coup d'état against his co-regent. He went to Yongning Palace to meet Empress Dowager Guo to request the memorialisation of a decree ordering the removal of Cao Shuang and his brothers from power. Thereafter, all the city gates were closed while Sima Shi's previously-arranged 3,000 forces which had gathered at the Sima Gate (司馬門) under his command were led to occupy the palace gates. Sima Yi later even commented: "This son really worked well." Soon, the troops were lined up along the palace grounds, passing through Cao Shuang's camp. Cao Shuang's Controller of Camp, Yan Shi (嚴世), was on the upper floor, drawing his crossbow, intending to shoot the passing Sima Yi. His colleague Sun Qian (孫謙) stopped him and said: "We wouldn't know what will happen." Three times he focused, three times he stopped, every time pulling back his elbow, but not getting to shoot.

Meanwhile, Sima Yi granted imperial authority to Gao Rou, the Minister over the Masses, and further appointed him as acting General-in-Chief (大將軍) and ordered him to take command of Cao Shuang's troops while stating: "You're now like Zhou Bo." He also appointed Wang Guan, the Minister Coachman (太僕), and a man whom Sima Yi had previously recommended during Cao Rui's reign, as acting Commandant of the Central Army (中領軍) and ordered him to seize command of the troops under Cao Shuang's brother Cao Xi (曹羲).

Sima Yi, along with the Grand Commandant (太尉) Jiang Ji and others, led troops out of Luoyang to the floating bridge above the Luo River, where he sent a memorial to the emperor, Cao Fang, listing out Cao Shuang's crimes (e.g. not fulfilling his duty as regent, corrupting the government, conspiring against the throne) and requesting the emperor to remove Cao Shuang and his brothers from their positions of power. Cao Shuang blocked the memorial from reaching Cao Fang and left the emperor at the south of the Yi River while ordering his men to cut down trees to build anti-cavalry blockades and station about 1,000 troops nearby to guard against Sima Yi's advances. Sima Yi sent Xu Yun (許允) and Chen Tai to persuade Cao Shuang to plead guilty as early as possible. He additionally sent Yin Damu (尹大目), a man whom Cao Shuang trusted, to tell him that nothing more would result from this aside from his dismissal. Huan Fan, the Minister of Finance (大司農), had previously left the city to visit Cao Shuang's camp, with Sima Yi commenting: "The 'bag of wisdom' is gone." Jiang Ji responded: "Huan Fan is indeed wise, but stupid horses are too much attached to the beans in their manger. Cao Shuang is certain not to employ his counsel." Huan Fan attempted to convince Cao Shuang and his brothers to flee to Xuchang with the emperor, and to issue an edict denouncing Sima Yi as a traitor and drafting troops to fight back, but they remained undecided. Cao Shuang ultimately surrendered to Sima Yi and gave up his powers, thinking that he could still lead a luxurious life in retirement. Huan Fan scolded them, saying: "Cao Zhen was a good man, yet sired you and your brothers, little pigs and calves that you are! I never expected to be involved with you and have my family annihilated."

After returning to Luoyang, Cao Shuang and his brothers were carefully guarded, and on 9 February 249, Cao Shuang was accused of plotting treason, after the palace eunuch, Zhang Dang (張當), who had himself been sent to the tingyu, had testified that Cao Shuang and his associates were planning to seize the throne for themselves. Cao Shuang was arrested along with his brothers and his supporters, including He Yan, Ding Mi, Deng Yang, Bi Gui, Li Sheng, and Huan Fan. They were subsequently executed along with the rest of their families and relatives on the same day. Jiang Ji had attempted to persuade Sima Yi to spare Cao Shuang and his brothers in consideration of the meritorious service rendered by their father, Cao Zhen, but Sima Yi refused. Two of Cao Shuang's subordinates, Lu Zhi (魯芝) and Yang Zong (楊綜), had been implicated in the plot and arrested as well, although Sima Yi pardoned them under the rationale that: "Each of them was serving his own master."

Earlier on, when Huan Fan escaped from Luoyang to join Cao Shuang, he encountered Si Fan (司蕃), who was guarding the Changping Gate. As Si Fan used to serve under Huan Fan, he trusted Huan Fan and allowed him to pass through. Once he was out of Luoyang, Huan Fan turned back and told Si Fan: "The Imperial Tutor (Sima Yi) is planning to commit treason. You should come with me!" However, Si Fan stayed behind and hid himself. After the coup d'état, Si Fan surrendered himself to Sima Yi and told him what happened earlier. Sima Yi asked: "What's the punishment for falsely accusing someone of treason?" The reply was: "According to the law, the one who makes the false accusation shall be punished for treason." Huan Fan was then executed along with the rest of his family.

Cao Shuang's younger cousin, Cao Wenshu, had perished, and the family of his widowed wife, Xiahou Lingnu, wanted to remarry her to someone else, in response to which she cut off both her ears, and later her nose. Her family asserted that the Cao clan was exterminated, but she retorted by saying: "I have heard that a person of worth does not renounce his principles because of changes in fortune, nor a righteous person change his mind with a view to preservation or destruction. While the Cao flourished, I was bent on keeping my chastity. Now that they have declined and perished, can I bear to renounce them? Even animals do not act this way; how can I?" When Sima Yi heard of this, he allowed her to adopt a son as an heir to the Cao clan.

The contemporary Shu official and regent, Fei Yi, gave his own comment regarding the coup as follows:

[...] If Sima Yi really considered Cao Shuang to be guilty of extravagance and arrogance, it would suffice for him to execute him according to the law. However, he exterminated even his infant children, branding them with the name of disloyalty, effectively wiping out Zidan's line. Also, He Yan's son was a nephew of the Wei ruler, and even he was killed. Sima Yi was assuming too much power and behaving improperly.

Fei Yi on Sima Yi's coup d'état

On 18 February (or sometime in March) 249, Cao Fang appointed Sima Yi as Imperial Chancellor (丞相) and added another four counties – Fanchang (繁昌), Yanling (鄢陵), Xinji (新汲), and Fucheng (父城) – to Sima Yi's marquisate, bringing the size of the marquisate to a total of eight counties and 20,000 taxable households. Cao Fang also awarded Sima Yi the privilege of not having to announce his name when he spoke to the emperor. Sima Yi declined the appointment of Imperial Chancellor. In January or February 250, Cao Fang awarded Sima Yi the nine bestowments and an additional privilege of not having to kowtow during imperial court sessions. Sima Yi declined the nine bestowments. In February or March 250, Cao Fang had an ancestral shrine built for the Sima family in Luoyang, increased the size of Sima Yi's personal staff, promoted some of Sima Yi's personal staff, and enfeoffed Sima Yi's sons Sima Rong (司馬肜) and Sima Lun as village marquises. At the time, as Sima Yi was chronically ill, he could not regularly attend imperial court sessions, so Cao Fang often visited him at his residence to consult him on policy matters.

Suppressing Wang Ling's rebellion

Wang Ling, the Grand Commandant (太尉), and his nephew Linghu Yu (令狐愚), the Inspector of Yan Province, became worried of Sima Yi's growing influence over the emperor, Cao Fang, so they plotted to replace Cao Fang with Cao Biao, the Prince of Chu, while instating his capital city as Xuchang, and then to overthrow Sima Yi. Linghu Yu, however, died in December 249 or January 250.

In February 251, Wang Ling either lied by stating that Eastern Wu forces were approaching the Tu River (塗水) and requested that the Wei government give him troops to resist the invaders, or was telling the truth in that they were actually obstructing the river, but wanted to use the troops for his own malicious purposes. Either way, Sima Yi was suspicious of Wang Ling's intention, and so he refused to approve the request. On 7 June 251, upon receiving intelligence of Wang Ling's plot from two officials named Yang Hong (楊弘) and Huang Hua (黃華), Sima Yi immediately mobilised troops to attack Wang Ling and moved by travelling down the river while bestowing additional authority upon Zhuge Dan and ordering him to lead his own forces to encroach upon Wang Ling's position. He first issued a pardon to Wang Ling and sent a secretary to call for his surrender, while Sima Yi's army ultimately reached Gancheng (甘城) within a few days and advanced to within 100 chi of Wang Ling's base to put pressure on him. Wang Ling knew that Sima Yi already knew about his plans to rebel, and he also knew that his forces were too weak, so he gave up, sent his subordinate Wang Yu (王彧) to apologise on his behalf, and handed over his official seal and ceremonial axe to Sima Yi. When Sima Yi's army reached Qiutou (丘頭), Wang Ling tied himself up, but Sima Yi, acting on imperial order, sent a Registrar (主簿) to unbind Wang Ling and reassure him of his safety and return to him his official seal and ceremonial axe.

He thereafter met with Sima Yi at Wuqiu (武丘), with a distance of more than ten zhang between both of them, and Wang Ling told him: "If I am guilty, you can summon me to meet you. Why do you need to come here?" Sima Yi replied: "That's because you don't respond to summons." Wang Ling exclaimed: "You have failed me!" Sima Yi responded by claiming: "I would rather fail you than fail the state." Wang Ling was then escorted as a prisoner back to Luoyang. To discern Sima Yi's true intentions, Wang Ling asked him if he could receive nails for his coffin. Sima Yi had them given to him. Along the way, when Wang Ling passed by a shrine honouring the Wei general Jia Kui, he exclaimed: "Jia Liangdao! Only the gods know Wang Ling is truly loyal to Wei." Wang Ling later committed suicide on 15 June 251 by consuming poison at Xiang County (項縣; present-day Shenqiu County, Henan). Sima Yi had Wang Ling's conspirators arrested and executed along with their families.

Cao Fang sent Wei Dan (韋誕) as an emissary to meet Sima Yi at Wuchi (五池) and congratulate him on his success in suppressing Wang Ling's rebellion. Later, when Sima Yi reached Gancheng, Cao Fang sent Yu Ni (庾嶷) as an emissary to appoint Sima Yi as Chancellor of State (相國) and promote him from a marquis to a duke under the title "Duke of Anping Commandery" (安平郡公). One of Sima Yi's grandsons and one of his brothers were also enfeoffed as marquises. At the time, the Sima family had a total of 19 marquises and 50,000 taxable households in all their marquisates combined. Sima Yi declined the appointment of Chancellor of State and refused to accept his enfeoffment as a duke.

Reportedly, Guo Huai's wife, the younger sister of Wang Ling, was taken into custody by imperial censors. Guo Huai apprehensively relented and let her be taken, not wanting to push things further, but when his five sons kowtowed before him until their foreheads started bleeding, he finally relented and ordered his subordinates to bring back his wife from the imperial censors. He thereafter wrote a letter to Sima Yi: "My five sons are willing to sacrifice their lives for their mother. If they lose their mother, I lose them too. Without my five sons, I will no longer exist. If I have violated the law by seizing back my wife from the imperial censors, I am willing to see the Emperor and take full responsibility for my actions." After reading Guo Huai's letter, Sima Yi made an exception for Guo Huai's wife and pardoned her.

During that time, the Weilüe recounts a story of how a man named Yang Kang (楊康), who had been a personal aide of Linghu Yu, divulged the conspiracy of Linghu Yu having wanted to engage in a rebellion when he was still alive in 249 or 250. Sima Yi, while stationed in Shouchun, personally asked Shan Gu (單固), another former aide: "Did Linghu Yu plot a rebellion?" He denied this, but Sima Yi doubted him as Yang Kang had previously asserted that Shan Gu had also been involved in the plot, so Shan Gu and his family were arrested, and he was tortured and interrogated. Shan Gu remained firm in his denial, and so Sima Yi had Yang Kang called in to compare their testimonies. Yang Kang was unable to defend his own rhetoric, so Shan Gu began cursing at Yang Kang. Yang Kang had thought he would be enfeoffed as a reward, but as his own testimony had been inconsistent, he was instead sentenced to death together with Shan Gu, with both of them being dragged out and executed.

Around that time, the corpses of Wang Ling and Linghu Yu had been dragged out of their tombs and their bodies had been exposed for three days in the nearest market place.

In July 251, Cao Biao was forced to commit suicide. Sima Yi then relocated the other nobles from the Cao family to Ye, where they were effectively put under house arrest there.

Death and posthumous honours

In July 251, when Sima Yi became critically ill, he dreamt of Jia Kui and Wang Ling being honoured, and he felt disturbed after that. He died on 7 September 251 in Luoyang at the age of 73 (by East Asian age reckoning). The emperor, Cao Fang, donned mourning garments, attended Sima Yi's funeral in person, and even ordered Sima Yi to be buried with the same honours as those accorded to Huo Guang in the Western Han dynasty. He also posthumously appointed Sima Yi as Chancellor of State (相國) and posthumously elevated him to the status of a duke. However, Sima Yi's younger brother, Sima Fu, declined the ducal title and a wenliangche (轀輬車) on behalf of his deceased brother, stating that Sima Yi would have done that if he were still alive.

Sima Yi was buried on 19 October 251 at Heyin County (河陰縣; north of present-day Mengjin County, Henan). Cao Fang granted him the posthumous title "Wenzhen" (文貞), which was later changed to "Wenxuan" (文宣). However, before his death, Sima Yi had made arrangements to be buried at Mount Shouyang (首陽山; in present-day Yanshi, Luoyang, Henan) with no markers (e.g. tombstone, trees) around his tomb, to be dressed in plain clothes, and have no luxury items buried with him. He also made a rule stating that his family members who died after him should not be buried with him.

After Sima Yi's death, his eldest son, Sima Shi, assumed his father's authority up until his own death on 23 March 255, after which Sima Yi's second eldest son, Sima Zhao, took up his elder brother's position. On 2 May 264, when the Wei emperor, Cao Huan, enfeoffed Sima Zhao as the vassal "Prince/King of Jin" (晉王), Sima Zhao went on to honour his father with the posthumous title "Prince/King Xuan of Jin" (宣王). Sima Zhao died on 6 September 265, and his eldest son, Sima Yan, succeeded him in his position. By the next year, in 266, after Sima Yi's grandson, Sima Yan, usurped the throne from Cao Huan and established the Jin dynasty with himself as the emperor, he honoured his grandfather with the posthumous title "Emperor Xuan of Jin" (宣皇帝), with the temple name "Gaozu" (高祖), and named his grandfather's burial place "Gaoyuan Mausoleum" (高原陵).


In his younger days, Sima Yi was a close friend of Hu Zhao (胡昭). In one incident, Zhou Sheng (周生) kidnapped Sima Yi and wanted to kill him. Hu Zhao braved danger to meet Zhou Sheng in the Xiao Mountains and tried to persuade him to let Sima Yi go. When Zhou Sheng refused, Hu Zhao cried and pleaded with him. Zhou Sheng was so moved by Hu Zhao's sincerity that he released Sima Yi. As Hu Zhao never told anyone about this incident, very few people knew that Sima Yi owed him his life.

A different and likely fictional version of how Sima Yi came to join Cao Cao's administration originally comes from a Weilüe account where it is stated that Cao Hong, a veteran general serving under Cao Cao, had heard of Sima Yi's talent and wanted to recruit him as an adviser. However, as Sima Yi thought little of Cao Hong, he refused to meet him and pretended to be so ill that he could not move around without using crutches. Cao Hong was so unhappy that he reported it to Cao Cao, who then summoned Sima Yi. When Sima Yi heard that Cao Cao wanted to meet him, he immediately threw aside his crutches and rushed there.

Cao Cao heard that Sima Yi was not only ambitious, but also had a lang gu (狼顧) appearance, so he wanted to test and see if it was true. One day, he ordered Sima Yi to walk in front of him and then made him look back. Sima Yi purportedly turned his head 180 degrees to look back. Cao Cao also once dreamt of three horses feeding from the same trough and he felt disturbed, so he warned Cao Pi: "Sima Yi won't be content with being a subject; he will interfere in your family matters." As Cao Pi was on good terms with Sima Yi, he often protected and shielded Sima Yi from criticisms. Sima Yi also took great care to create an image of himself as a diligent and faithful subject in front of Cao Cao to reduce the latter's suspicions of him.

In his later years, Sima Yi supposedly started neglecting his wife, Zhang Chunhua, in favour of his concubine Lady Bai (柏夫人) . Once, when he was ill, Zhang Chunhua paid him a visit, and he said: "Old creature, your looks are disgusting! Why do you even bother to visit me?" In response to which she, in anger, attempted to starve herself to death, during which her children soon joined her. Sima Yi immediately began apologising and reconciling with her. Sima Yi later secretly told someone: "It doesn't matter if that old creature died. I was actually worried about my boys!"

Appraisal and legacy

In 238, when Gongsun Yuan heard that Sima Yi was leading a Wei army to Liaodong to attack him, he sent a messenger to request reinforcements from Wei's rival state Eastern Wu. The Wu emperor, Sun Quan, eventually complied, and he wrote to Gongsun Yuan: "Sima Yi is well-versed in military arts. He uses military strategy like a god. He defeats all who stand in his way. I am deeply worried for you, my brother."

In 249, Wang Guang, the son of Wang Ling, allegedly commented: "Now Sima Yi cannot be fathomed, but what he does never runs contrary to the situation. He gives his assignments to the worthy and capable, and liberally credits those who are better than he; he practices the laws of the former rulers and satisfies the people's desire. Of whatever Cao Shuang did wrong, he has left nothing uncorrected. He does not relax his efforts day and night, his primary aim being to soothe the people."

The Eastern Jin dynasty's Emperor Ming (r323–325), a descendant of Sima Yi, once asked an official named Wang Dao to tell him about the origins of the Jin dynasty, so Wang Dao told him everything from Sima Yi's career to Cao Mao's attempted coup against Sima Zhao. After hearing from Wang Dao, Emperor Ming remarked: "If what you said is true, how can the Jin (dynasty) expect to last long?"

The Tang dynasty historian Fang Xuanling, who was the lead editor of Sima Yi's biography in the Book of Jin, noted that Sima Yi was known for appearing to be generous and magnanimous on the outside while being distrustful and jealous on the inside. He wrote that Sima Yi was suspicious, calculative, manipulative, and a skilled practitioner of power politics. He also pointed out Sima Yi's cruelty in massacring Liaodong's population and exterminating Cao Shuang and his entire clan.

After the fall of the Western Jin dynasty in 316, the belief began to slowly shift from the popular ideal that Wei was the rightful successor to the Han dynasty towards the alternative view that Shu may have had greater legitimacy. Likewise, before 316, Sima Yi was seen as a righteous figure and was practically deified; after 316, however, he started to be viewed in a more critical manner, which has lasted into the modern age, and which is exemplified by Li Shimin's (Emperor Taizong of Tang's) comment regarding Sima Yi from the Book of Jin:

When the Son of Heaven [Cao Fang] was outside, he [Sima Yi] raised armoured troops from the inside. The burial soil was not quite settled, and yet he hurriedly executed and massacred [them]; how can this be a virtuous minister's conduct? An utmost good form was confused by this. In plans for campaign, how can there be eastern wisdom and western stupidity? How can the heart of a ruler's assistant be formerly loyal and later rebellious? Therefore Jin Ming [Sima Shao] covered his face, ashamed that he through deception and falseness had accomplished achievement. Shi Le possessed unrestrained words, laughing that treachery returned to settle the enterprise. The ancients had a saying: 'One can do good deeds for three full years, and yet few will know of it, but a single day's evil will be known by all under Heaven.' Isn't that just so? You might keep it hidden for a few years, but posterity will still sneer at you in the end. You might as well be the man who covers his ears when he steals the bell, thinking that no one else can hear it either; you might as well be the thief who steals gold when the marketplace is at its busiest, claiming that you could not even see the people. The greed that you indulge today will echo in eternity; the profit that you pursue today will destroy your reputation.

Li Shimin on Sima Yi



  • Sima Fang, Marquis Cheng of Wuyang (posthumous) (舞陽成侯 司馬芳; 149–219)

Consorts and Issue

  • Zhang Chunhua, Empress Xuanmu (posthumous) (宣穆皇后 張春華; 189–247)
    • Sima Shi, Emperor Jing (posthumous) (景皇帝 司馬師; 208–255), first son
    • Sima Zhao, Emperor Wen (posthumous) (文皇帝 司馬昭; 211–265), second son
    • Princess Nanyang (南陽公主), first daughter
      • Married Xun Yi (荀霬), and had issue (two sons)
    • Sima Gan, Prince of Pingyuan (平原王 司馬幹; 232–311), sixth son
  • Lady Fu (伏夫人)
    • Sima Liang, Prince (Wencheng) of Ru'nan (汝南文成王 司馬亮; exec. 291), third son
    • Sima Zhou, Prince (Wu) of Langxie (琅邪武王 司馬伷; 227–283), fourth son
    • Sima Jing, Marquis of Qinghui (清惠侯 司馬京; 230–253), fifth son
    • Sima Jun, Prince (Wu) of Fufeng (扶風武王 司馬駿; 232–286), seventh son
  • Lady Zhang (張夫人)
    • Sima Rong, Prince (Xiao) of Liang (梁孝王 司馬肜; d. 302), eighth son
  • Lady Bai (柏夫人)
    • Sima Lun, Prince of Zhao (趙王 司馬倫; p. 301), ninth son
  • Unknown
    • Princess Gaolu (高陸公主), second daughter
      • Married Du Yu, Marquis (Cheng) of Dangyang (當陽成侯 杜預; 222–285)

In Romance of the Three Kingdoms

Sima Yi is a major character in the 14th-century historical novel Romance of the Three Kingdoms, which romanticises the historical figures and events before and during the Three Kingdoms period of China. In the novel, he is cast as a villainous figure who pretends to be a loyal and dedicated subject of the Wei state, while secretly planning to concentrate power in his hands and pave the way for his descendants to usurp the throne one day – in the same way Cao Cao did towards the end of the Eastern Han dynasty. He also serves as a nemesis to Zhuge Liang during the Shu invasions of Wei between 228 and 234, with both of them trying to outwit each other in the various battles.

In popular culture

Sima Yi is sometimes venerated as a door god at Chinese and Taoist temples, usually in partnership with Zhuge Liang.

Chan Mou's manhua series The Ravages of Time is a fictionalised retelling of the history of the late Eastern Han dynasty and the Three Kingdoms, with Sima Yi as the central character.

Sima Yi also appears as a playable character in Koei's Dynasty Warriors and Warriors Orochi video game series. In the mobile game Puzzles & Dragons, he is featured as a God type in their Three Kingdoms 2 Pantheon alongside Ma Chao and Diaochan. In the collectible card game Magic: The Gathering there is a card named "Sima Yi, Wei Field Marshal" in the Portal Three Kingdoms set.

Notable actors who have portrayed Sima Yi on screen include: Wei Zongwan, in Romance of the Three Kingdoms (1994); Ni Dahong, in Three Kingdoms (2010); Eric Li, in Three Kingdoms RPG (2012); Wu Xiubo, in The Advisors Alliance (2017); and Elvis Han, in Secret of the Three Kingdoms (2018).

The contents of this page are sourced from Wikipedia article on 24 Mar 2020. The contents are available under the CC BY-SA 4.0 license.
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