Family background

Sima Yi's ancestral home was in Xiaojing (孝敬里), Wen County, Henei Commandery. 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 in the process. In the early Han dynasty, Sima Ang's former kingdom, which had been largely situated in Henei, became a commandery of the Han Empire, and his descendants had lived there since.

Sima Jūn, 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. Sima Jūn's son, Sima Liang, held the position of Grand Administrator of Yuzhang, and Sima Liang's son, Sima Jùn, served as Grand Administrator of Yingchuan. Sima Jùn's son, Sima Fang, served as the Prefect of Luoyang (洛陽令), Intendant of Jingzhao, 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, 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, Consultant (議郎), Officer in the East Bureau of the Imperial Chancellor's Office, 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. 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", 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, 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, 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 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, 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 and Imperial Chancellor of the Han Empire in early 220, he enfeoffed Sima Yi as the Marquis of Hejin-ting (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 and Xiangyang lacked food supplies. At the time, Cao Ren, who was defending Xiangyang, had been reassigned from Fancheng to defend Wan. 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 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".

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 Wan, 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, Yang Jun, 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".

In the spring of 225, he was appointed General Who Pacifies the Army 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, 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". Around that time, Sun Quan attacked Jiangxia Commandery and sent his generals Zhuge Jin and Zhang Ba 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.

Suppressing Meng Das rebellion

In July 227, Cao Rui ordered Sima Yi to garrison at Wan 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 Anqiao (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 Wan 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, 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 Wan.

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.

Aborted campaign against Shu

In March 230, Sima Yi was promoted to General-in-Chief, 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. 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 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 and Mei 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; in 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 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, 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

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.

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 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 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 Tribulus terrestris 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 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 North China Plain, 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

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 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, 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:

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 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), 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, 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; now known as 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 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 jingguan (京觀, a victory mound) 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, 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 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 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 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 and Sun Zi, 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. 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, 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. 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 Wan to congratulate him and host a banquet to celebrate the victory.

In August 241, the Wei imperial court added two 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; around 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; around 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 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.

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, over 10,000 households living in the area fled to the north across the Mian River (沔水, a historical name for the Han River). 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 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, 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 Mausoleum (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 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 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 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 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 Jiang Ji and others, led troops out of Luoyang to the pontoon 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, 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, 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:

— 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 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 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 Lings rebellion

Wang Ling, the Grand Commandant, 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 and Huang Hua, 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; around 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 and promote him from a marquis to a duke under the title "Duke of Anping Commandery". 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, 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 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", Sima Zhao went on to honour his father with the posthumous title "Prince/King Xuan of Jin". 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", with the temple name "Gaozu", and named his grandfather's burial place "Gaoyuan Mausoleum" (高原陵).

Anecdotes

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 to look back without moving his body. 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 (323–325), 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:

— Li Shimin on Sima Yi

Family

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 Runan (汝南文成王 司馬亮; exec. 291), third son

　• Sima Zhou, Prince Wu of Langya (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).

生平

早年經歷

司馬懿家族數代為官，高祖父司馬鈞為漢安帝時的征西將軍，曾祖父司馬量為豫章太守，祖父司馬儁為潁川太守，父親司馬防為京兆尹。司馬防有八子，因字中都有一個「達」字，當時號稱司馬八達。司馬懿是司馬防的次子，出生于漢靈帝光和二年（179年）。司馬懿少年時期就胸懷謀略，當時正是東漢末年亂世，司馬懿「常慨然有憂天下心」。素以知人善任著稱的南陽太守楊俊曾見過少年司馬懿，他說司馬懿絕非尋常之子。尚書崔琰與司馬懿的兄長司馬朗交好，曾對司馬朗說：「你弟弟聰明懂事，做事果斷，英姿不凡，不是你所能比得上的。」

建安六年（201年），郡中推舉他為計掾。當時曹操正任司空，聽到他的名聲後，派人召他到府中任職。司馬懿見漢朝國運已微，不想在曹操手下，便藉口自己有風痺病，身體不能起居。曹操不信，派人夜間去刺探消息，司馬懿躺在那裡，一動不動，像真染上風痺一般。

建安十三年（208年），曹操為丞相以後，使用強制手段闢司馬懿為文學掾。曹操對使者說，「若複盤桓，便收之」。司馬懿畏懼，只得就職。曹操讓他與公子往來游處，歷任黃門侍郎、議郎、丞相東曹屬、丞相主簿等職。

《魏略》記載召闢過程有所不同。說是司馬懿好學，曹洪自以為才疏，想讓司馬懿去幫助他，司馬懿恥于和曹洪來往，藉口病到拄拐杖的地步無法去見曹洪。曹洪記恨司馬懿，去跟曹操打小報告，曹操徵召司馬懿，司馬懿立刻扔了拐杖去見曹操為其效命。

《晉書》記載曹操逐漸察覺司馬懿「有雄豪志」，又發現他有「狼顧之相」，心裡很忌諱。因此對曹丕說，司馬懿不是甘為臣下的人，必會干預我們的家族之事。但因曹丕和司馬懿關係很好，而得以無事。

司馬懿先後擔任黃門侍郎、議郎、丞相東曹屬和丞相主簿，並跟隨曹操征討張魯。司馬懿見劉備剛剛奪取益州，腳跟未穩，勸曹操接著攻打劉備，曹操不聽。曹操班師後司馬懿跟隨曹操參加第三次濡須口之戰。

軍事才略

進諫伐蜀

建安二十年（215年），曹操平定張魯勢力後，司馬懿和劉曄進諫認為：「劉備只是一時以奸詐手段奪取劉璋之地，蜀人人心未歸而又計劃爭奪江陵，此乃最適當時機趁勢進軍漢中，必定能使益州人心震動，繼而瓦解其勢力，萬勿錯失良機。」未料卻遭曹操反駁：「剛平定隴右便指望馬上伐蜀，是過於進取也。」及後大軍退還。有蜀投降者透露：「進軍漢中消息一出，劉備軍中便人心惶惶，雖斬之也無法安定。」此次錯失後，曹操要在兩年後才能發動漢中之戰，此時劉備軍心已得初定，最終被劉備奪取漢中。

聯孫抗劉

建安二十四年（219年），司馬懿任丞相軍司馬，指出荊州刺史胡修粗暴、南鄉太守傅方驕奢，都不應派任駐守邊防，曹操未予重視；七月，關羽攻荊襄，圍魏將曹仁，水淹于禁七軍；胡、傅二人果然乘機降劉。

因漢獻帝在許都，距樊城很近，曹操感到威脅，為避關羽鋒芒，一度準備遷都河北。蔣濟、司馬懿等人當時勸阻：「于禁是被洪水所淹，不是戰敗失守，所以國家大計並沒受損，現在遷都既示弱於敵，又使人心不安；劉備、孫權外親內疏，現在關羽得意，孫權必定更不高興，把這事告之孫權，坐山觀虎鬥，則樊城之圍自解」。曹操聽從他的計策，孫權果然派呂蒙襲取江陵，用假冒商船之計連破關羽設下的烽火臺，攻佔眾多城池，關羽只好回援，魏軍趁勢追殺，關羽損失大量兵馬，最終於麥城附近中東吳埋伏而敗亡。曹孫聯盟勝利，樊城之危解除。

徐晃擊退關羽後，曹操嫌惡荊州及附近百姓，想把他們都遷走。司馬懿認為：「荊楚輕脫，易動難安。關羽新破，諸為惡者藏竄觀望。今徙其善者，既傷其意，將令去者不敢複還。」曹操從之，沒有移民。藏竄逃亡者果然都複出歸化。

曹丕繼魏王位後，封河津亭侯，轉丞相長史。當時孫權率兵向西，朝議以樊城、襄陽無穀，不可以禦，請召當時鎮襄陽的曹仁回宛。司馬懿說：「孫權新破關羽，這是想和魏結交的時候，必不敢為患。襄陽是水陸之沖，禦寇要害，不可棄。」不被聽從。於是曹仁焚棄樊城、襄陽，孫權果然沒有來犯，曹丕悔之。曹魏代漢後，以司馬懿為尚書。不久，轉督軍、禦史中丞，封安國鄉侯。黃初二年（221年），遷侍中、尚書右僕射。

抵禦孫吳

黃初七年（226年），曹丕逝世。孫權得知後，於八月出兵攻魏。命吳左將軍諸葛瑾部兵分兩路進攻襄陽，親自率軍進攻江夏郡。孫權一路為魏軍所敗，撤兵而走。司馬懿擊敗諸葛瑾，並斬殺吳將張霸，斬首千餘級。十二月，升任驃騎將軍。

擒斬孟達

魏太和二年（227年），司馬懿率宛城之兵迅速平定孟達叛魏，再次展現出軍事才略。孟達原為蜀漢降將，曹丕命他守新城（今湖北房縣）。曹丕死後，孟達欲叛魏歸蜀。司馬懿偵知消息後，一方面寫信麻痺孟達，一方面遣軍進討，八日內行軍一千二百里。孟達給諸葛亮信中認為司馬氏率軍來討，至少需要一個月時間，所以當司馬懿提前二十餘日趕來時，完全打亂了他的叛亂計劃。司馬懿前後總共只用了十六日，即破上庸，斬殺孟達。

抵禦蜀漢

魏太和四年（230年），曹魏派司馬懿由西城，張郃由子午道，曹真由斜谷，三路進攻漢中，諸葛亮率軍西征，命李嚴率軍2萬赴漢中。合攻漢中，但因天雨而罷兵。

魏太和五年（231年）春，諸葛亮第四次北伐。魏明帝讓司馬懿駐紮長安。諸葛亮先是圍祁山，又招鮮卑軻比能響應。司馬懿命令費曜、戴淩等留四千兵守上邽，其餘兵力皆往祁山救援，司馬懿親率大軍前往隃麋。就在司馬懿以為諸葛亮主攻祁山時，不料諸葛亮卻反其道而行，得知司馬懿大軍要來，分兵留攻祁山，自己卻率主力奇襲上邽，迎擊司馬懿。郭淮、費曜等出擊諸葛亮，卻被諸葛亮大敗。司馬懿與諸葛亮遇於上邽之東，諸葛亮不斷後撤將司馬懿引誘至鹵城祁山。司馬懿旣至，登山掘營，不肯戰。軍將領數次請戰，司馬懿都不准，被譏笑：「公畏蜀如虎，奈天下笑何！」，在眾將的一再要求下，五月十八日，司馬懿命襲擊蜀將王平所部，卻反遭諸葛亮逆襲，魏軍為魏延、高翔、吳班等人所破，退保營寨。

六月，諸葛亮向漢中撤退，司馬懿命張郃率軍追擊，張郃中箭身亡。（《魏略》）

魏青龍二年四月（234年），諸葛亮占據渭河南武功五丈原，想北渡渭河，被大將郭淮阻攔而失敗。諸葛亮只能在渭河南與魏國大都督司馬懿對峙。由於戰術上的敗勢，司馬懿據險堅守，對峙百餘日後，蜀軍糧盡而自退。諸葛亮曾多次向司馬懿挑戰。司馬懿寫奏章向魏明帝請戰，明帝下令不許出戰，並派衛尉辛毗持符節制止魏軍。姜維對諸葛亮說：「辛佐治仗節而到，賊不復出矣。」諸葛亮說：「彼本無戰情，所以固請戰者，以示武於其眾耳。將在軍，君命有所不受，苟能制吾，豈千里而請戰邪！」諸葛亮再派人至司馬懿軍中，司馬懿只向漢使詢問諸葛亮寢食和管理政事的繁雜，不過問軍旅之事。諸葛亮使者對司馬懿說：「諸葛公夙興夜寐，罰二十以上，皆親攬焉；所啖食不至三升。」司馬懿說：「亮將死矣。」其後，兩軍對峙一百多天。諸葛亮的北伐都以失敗告終。八月，諸葛亮終於病倒。劉禪派尚書僕射李福到前線去探望，回到成都時，諸葛亮在五丈原前線病逝，享年五十四歲。當楊儀等人整軍而還時，司馬懿得知蜀漢撤退，親自率兵來追；姜維見司馬懿追來，反旗鳴鼓，司馬懿不知諸葛亮已死，下令停止追擊，全軍返回。於是楊儀結陣而去，從容退進斜谷，百姓流傳一諺語：「死諸葛驚走生仲達。」司馬懿聽到後，說：「吾能料生，不便料死也。」（我能預料他活著的時候想做什麼，不能預料他死後想怎麼做。）司馬懿到諸葛亮駐軍營壘處所察看，感嘆說：「真是天下的奇才啊！」。追到赤岸，沒有追上蜀軍而退軍。此後，司馬懿成為曹魏政權的中流砥柱，地位日益提高。次年正月戊子日（235年2月13日）升遷為太尉。

平定遼東

青龍五年（237年），原魏遼東太守公孫淵自立為燕王，置列百官，對抗朝廷。景初二年（238年）正月，魏明帝曹叡遣59歲的司馬懿率軍4萬，前往征討，途中司馬懿路過故鄉溫縣，會見父老鄉親，感慨萬千，做詩一首：「天地開闢，日月重光。遭遇際會，畢力遐方。將掃群穢，還過故鄉。肅清萬里，總齊八荒。告成歸老，待罪舞陽。」六月進至遼水。

公孫淵急令大將軍卑衍、楊祚等人率步騎數萬，依遼水圍塹20餘裡，堅壁高壘，阻擊魏軍。司馬懿採用聲東擊西之計，佯攻圍塹，而以主力隱蔽渡過遼水，直取公孫淵根據地襄平，迫使敵軍放棄圍塹回軍救援襄平。司馬懿督軍回首山，迎戰敵援軍，三戰皆捷，遂乘勝進圍襄平。

當初公孫淵聞魏軍來攻，曾求救于孫權，孫權也出兵為其聲援，並寫信給公孫淵說：「司馬懿善用兵所向無前，深為弟憂也。」

適逢連降大雨，遼水暴漲，平地數尺，魏軍恐懼，諸將思欲遷營。司馬懿下令有敢言遷營者斬，都督令史張靜違令被斬首，軍心始安。公孫淵軍乘雨出城，魏將領請求出擊，司馬懿不予採納。一月有餘，雨停，水漸退去。魏軍完成對襄平的包圍，起土山、挖地道、造樓車、鉤梯等攻城器具，晝夜強攻。守軍糧食將盡，軍心動搖，楊祚等先降。

八月，襄平城破，公孫淵率數百騎兵突圍，被殺于梁水。司馬懿把襄平城內平民男子年十五以上七千餘人及公孫淵政權官員將軍等二千餘人全部殺死，並將屍體堆積起來，號稱「京觀」。遼東四郡為魏所據。

擊退孫吳

正始二年夏四月（241年），東吳派遣衛將軍全琮攻淮南，遏東興堤水攻魏軍，火燒安城邸閣，收歸當地平民。威北將軍諸葛恪攻六安，全琮大戰王凌於芍陂，魏將秦晃的手下戰死有十餘人。車騎將軍朱然、孫倫等五萬人圍攻樊城，大將軍諸葛瑾攻取柤中。 全琮與王凌爭芍陂水塘，力戰連日，全琮不敵被王凌所擊退， 全琮被破走而樊城圍急，司馬懿說：「柤中民夷十萬，隔在水南，流離無主，樊城被攻，歷月不解，此危事也，請自討之。」 議論者勸誡說：「吳軍遠圍樊城不可拔，挫於堅城之下，有自破之勢，宜長策以御之。」司馬懿反駁說：「軍誌有之：將能而御之，此為縻軍；不能而任之，此為覆軍。今疆埸騷動，民心疑惑，是社稷之大憂也。」六月，督諸軍南征，車駕送津陽城門外。司馬懿以南方暑溼，不宜持久，使輕騎挑之，然不敢動。於是乃令諸軍休息洗沐，簡精銳，募先登，申號令，示必攻之勢。然等聞之，乃夜遁。追至三州口，大殺獲，斬獲萬餘人 。 六月辛丑，司馬懿救樊城後退兵。

正始三年（242年）春，魏帝追封司馬懿父親司馬芳舞陽成侯。三月，司馬懿上奏修廣漕渠，引河入汴，疏通東南各個大湖，於淮北大規模屯田。吳國派諸葛恪屯駐皖城，邊人深以為苦。司馬懿要率兵攻之，朝臣認為諸葛恪佔據堅城，廣有糧穀，孤軍遠攻，救兵必至。司馬懿反駁認為吳軍所擅長的是水戰，而不是陸戰。湖水冬淺，船不能行，救兵必棄船就陸相救，於陸戰破敵就很容易了。正始四年（243年）九月秋，司馬懿率軍出征諸葛恪，車駕送出津陽門。軍隊到達舒城，諸葛恪果然焚燒積聚，棄城而走。司馬懿認為抵抗吳軍之要，在於積穀，於是派遣鄧艾到陳、項以東，至壽春地大興屯守，廣開淮陽、百尺二渠，又修諸陂於潁之南北，萬餘頃。自是淮北倉庾相望，壽春至於京師，農官屯兵連屬焉。

誅殺曹爽

曹操封魏王後，以司馬懿為太子中庶子以輔佐曹丕。曹丕臨終時，令司馬懿與曹真等為輔政大臣，輔佐魏明帝曹叡。明帝時，司馬懿屢遷撫軍大將軍、大將軍、太尉等要職。明帝崩，託孤幼帝曹芳以司馬懿和曹爽。

曹芳繼位後，曹爽最初因司馬懿德高望重，像對父親一樣對他，不敢自專。但不久曹爽聽親信丁謐之謀，排擠司馬懿，明升暗降，遷他為無實權的最高虛銜太傅，自己專擅朝政。正始十年（249年），司馬懿趁曹爽陪曹芳離洛陽至高平陵掃墓，發動政變並控制京師，將曹爽族滅。自此曹魏軍權政權落入司馬氏手中，史稱高平陵之變，又稱正始之變。司馬懿時年70歲。

事後，司馬懿被冊命為丞相，進爵安平郡公，增食邑萬戶，群臣奏事不得稱名，但他上書十餘次辭讓，故其官爵仍為太傅、舞陽侯。朝廷加他九錫，仍然辭而不受。奪權之後司馬懿藉口生病連皇帝曹芳都不去朝見，遇到國事，皇帝曹芳反而要去司馬懿宅邸親自詢問司馬懿。

嘉平二年（250年），皇帝曹芳下詔在曹魏首都洛陽設立司馬懿的家廟。

王淩之亂

嘉平三年（251年）太尉王淩與外甥兗州刺史令狐愚密謀廢立，迎曹操子曹彪登帝位。陰謀洩漏，司馬懿夷王淩、令狐愚三族，並賜死57歲的曹彪，為史載壽春三叛之一。之後司馬懿把曹魏宗室遷至鄴監視，不准他們結交他人。

身後追贈

嘉平三年（251年），司馬懿病逝於洛陽，享年72歲。承其遺願，辭讓郡公和殊禮，不樹不墳，不設明器，葬于首陽山。諡文（舞陽文侯），後改宣文（舞陽宣文侯）。264年，子司馬昭獲封晉王，旋即追尊司馬懿為晉王，諡號宣王。265年，孫司馬炎稱帝，建立西晉，追尊為皇帝，廟號高祖，諡號宣皇帝。

治國之道

司馬懿在上邽興屯田，京兆、天水、南安興冶鐵，穿成國渠，築臨晉坡使雍涼足食，並有餘力供給關中不足。後來又大興屯田於淮北，穿廣槽渠。

司馬懿曾向曹操建議軍事屯田制，而曹操採納後不久便病逝了（曹操死前已經有屯田制）。管理軍屯的主要官吏——度支中郎將、度支校尉、度支都尉等官員，都是在曹丕稱帝後的黃初年間（220—226年）設置的。所以，事實上軍屯的推廣在曹丕時期。曹魏軍屯其主要基地設置在和孫吳、蜀漢對立的地帶（淮河南北以及上邽、長安、槐裡、陳倉等地），而這裡基地的開創都經過司馬懿的督工：

太和四年，司馬懿上表建上邽軍屯。主持具體事宜的是度支尚書、司馬懿的三弟司馬孚。

青龍元年（233年），司馬懿興修水利，而「開成國渠，自陳倉至槐裡築臨晉陂，引汧洛溉舄鹵之地三千餘頃」使得『國以充實』。

青龍三年（236年），關東饑荒，司馬懿調5百萬斛粟運往洛陽，足見關中存有大量糧食。

曹操時魏國就曾「開募屯田於淮南」（《三國志·魏書·倉慈傳》），但僅是民屯。正始二年（241），司馬懿主持對吳作戰時，始與鄧艾籌畫在淮南淮北創建軍屯。。正始四年（243），司馬懿又『在於積穀，乃大興屯田，廣開淮陽、百尺二渠，又修諸陂於潁之南北，萬餘頃。自是淮北倉庾相望，壽陽至於京師，農官屯兵連屬焉。』『因欲廣田積穀，為兼併之計，乃使鄧艾行陳、項以東，至壽春地』（《晉書·食貨志》），使得『遂北臨淮水，自鐘離而南橫石以西，盡沘水四百餘裡，五裡置一營，營六十人，且佃且守。兼修廣淮陽、百尺二渠，上引河流，下通淮潁，大治諸陂于潁南、潁北，穿渠三百餘裡，溉田二萬頃，淮南、淮北皆相連接。自壽春到京師，農官兵田，雞犬之聲，阡陌相屬』。

在識拔人才上，司馬懿從寒門中提拔鄧艾、王基、州泰、賈越等人，如虞預所說，經略之才可謂遠矣。

景初二年（238年），司馬懿遠征遼東。時曹魏大修宮室，加上軍用物資，以至百姓饑弊。出征前，司馬懿勸明帝說：「昔周公營洛邑，蕭何造未央，今宮室未備，臣之責也。然自河以北，百姓困窮，外內有役，勢不並興，宜假絕內務，以救時急。」司馬懿勸諫曹叡不要大修宮殿勞民傷財，以保國之根本。曹叡死後他奏請罷修宮室，雕玩物之人力，節用務農，使天下欣賴。

軼聞

《晉書·宣帝紀》記載，司馬懿心裡猜忌而表面寬和，內心多疑但能靈活應對。曹操察覺司馬懿有雄心豪志，且聽聞司馬懿有狼顧的模樣。曹操打算驗明，所以先叫司馬懿在前頭走，再故意喊司馬懿，只見司馬懿身體不動，只有頭轉向後看。曹操又曾經發了一個噩夢，三匹馬同在一個槽裡進食，醒來後十分不快。曹操感到不好，召曹丕說道：「司馬懿不會甘做人臣，將來必幹預你的朝政家事。」這是三馬同槽的典故，此槽不是馬槽，是暗指著司馬氏吃掉曹氏，而且按照後來的史實走向來看，「三馬」還可以解讀為司馬懿、司馬師和司馬昭父子三人，他們共同為之後的司馬炎代魏創造了有利條件。但曹丕和司馬懿關係很好，總是維護他而得以無事。而司馬懿更加勤於職守，廢寢忘食，甚至喂馬之類的小事都親力親為，也終於使曹操安心。

司馬懿年少時和三國時的著名隱士胡昭關係很好，同郡的周生要加害司馬懿，胡昭聽說後涉險趕來搭救，「邀生於崤、澠之間，止生，生不肯。昭泣與結誠，生感其義，乃止」。

《三國志》卷16《倉慈傳》注引《魏略》載：青龍中，司馬宣王在長安立軍市，而軍中吏士多侵侮縣民，裴以白宣王，宣王乃發怒召軍市候，便於斐前杖一百……宣王遂嚴持吏士，自是之後，軍營、郡縣各得其分。

評價

南陽太守同郡楊俊：「此非常之人也。」認為有非常之器（《三國志·楊俊傳》、《晉書·宣帝紀第一》）

崔琰對司馬懿兄長司馬朗說：「君弟聰亮明允，剛斷英特，非子所及也。」（《晉書·宣帝紀第一》）

曹操：「有雄豪志，聞有狼顧相。」因而對曹丕說：「司馬懿非人臣也，必預汝家事。」（《晉書·宣帝紀第一》）

曹植曾形容司馬懿：「魁傑雄特，秉心平直。威嚴允憚，風行草靡。在朝則匡贊時俗，百僚儀一；臨事則戎昭果毅，折衝厭難者，司馬驃騎也。」（《全三國文·卷十八·魏十八》）

曹叡：「西方有事，非君（司馬懿）莫可付者。」（《晉書·宣帝紀第一》）「司馬懿臨危制變，擒淵可計日待也。」「吾得司馬懿二人，複何憂哉！」（《晉書·卷三十七·列傳第七》）

曹芳：「太尉體道正直，盡忠三世，南擒孟達，西破蜀虜，東滅公孫淵，功蓋海內。」（《《三國志·魏書四·三少帝紀第四》》）

夏侯霸：「彼自吻家，非人臣也」（《太平御覽·卷四百四十二 ◎人事部八十三○知人上》引 孫盛《魏氏春秋》）

吳質：「驃騎將軍司馬懿，忠智至公，社稷之臣也。」

陳矯：「朝廷之望；社稷，未知也。」（《三國志·卷二十二·魏書二十二·桓二陳徐衛盧傳第二十二》裴松之注引《世語》）

孫權：「司馬公善用兵，變化若神，所向無前。」

毌丘儉、文欽起兵反對司馬師時，依然對去世的司馬懿評價很高：「故相國懿，匡輔魏室，曆事忠貞，故烈祖明皇帝授以寄讬之任。懿戮力盡節，以甯華夏。又以齊王聰明，無有穢德，乃心勤盡忠以輔上，天下賴之。懿欲討滅二虜以安宇內，始分軍糧，克時同舉，未成而薨。齊王以懿有輔己大功，故遂使師承統懿業，委以大事。而師以盛年在職，無疾讬病，坐擁強兵，無有臣禮，朝臣非之，義士譏之，天下所聞，其罪一也。懿造計取賊，多舂軍糧，剋期有日。師為大臣，當除國難，又為人子，當卒父業。哀聲未絕而便罷息，為臣不忠，為子不孝，其罪二也。」

《晉書》評司馬懿平定公孫淵時殺戮太甚，誅殺曹爽時甚至連女子都殺害，然後篡奪魏國：「及平公孫文懿，大行殺戮。誅曹爽之際，支黨皆夷及三族，男女無少長，姑姊妹女子之適人者皆殺之，既而竟遷魏鼎雲。」

晉明帝時，王導侍坐。明帝問王導晉朝何以立國得天下，王導乃陳述司馬懿創業之始，及司馬昭末年弒高貴鄉公之事。明帝以面覆在牀上說：「若如公言，晉祚復安得長遠！」跡司馬懿之猜忍，蓋有符於狼顧。（《晉書·宣帝紀第一》）

虞預：「服膺文藝，以儒素立德，而雅有雄霸之量。值魏氏短祚，內外多難，謀而鮮過，舉必獨克，知人拔善，顯用仄陋。王基、鄧艾、周秦、賈越之徒，皆起自寒門，而著績於朝，經略之才，可謂遠矣。」

張悌：「諸葛、司馬二相，遭值際會，讬身明主，或收功於蜀漢，或冊名于伊、洛。丕、備既沒，後嗣繼統，各受保阿之任，輔翼幼主，不負然諾之誠，亦一國之宗臣，霸王之賢佐也。」

關於司馬氏代魏而仍能天下一統的原因，當時東吳屯騎校尉（官職）張悌的話，也許是很好的解釋：

永安六年，魏伐蜀，吳人問悌曰：「司馬氏得政以來，大難屢作，智力雖豐，而百姓未服也。今又竭其資力，遠征巴蜀，兵勞民疲而不知恤，敗於不暇，何以能濟？昔夫差伐齊，非不克勝，所以危亡，不憂其本也，況彼之爭地乎！」悌曰：「不然。曹操雖功蓋中夏，威震四海，崇詐杖術，征伐無已，民畏其威，而不懷其德也。丕、叡承之，系以慘虐，內興宮室，外懼雄豪，東西馳驅，無歲獲安，彼之失民，為日久矣。司馬懿父子，自握其柄，累有大功，除其煩苛而布其平惠，為之謀主而救其疾，民心歸之，亦已久矣。故淮南三叛而腹心不擾，曹髦之死，四方不動，摧堅敵如折枯，蕩異同如反掌，任賢使能，各盡其心，非智勇兼人，孰能如之？其威武張矣，本根固矣，群情服矣，奸計立矣。今蜀閹宦專朝，國無政令，而玩戎黷武，民勞卒弊，競於外利，不脩守備。彼強弱不同，智算亦勝，因危而伐，殆其克乎！若其不克，不過無功，終無退北之憂，覆軍之慮也，何為不可哉？昔楚劍利而秦昭懼，孟明用而晉人憂，彼之得志，故我之大患也。」吳人笑其言，而蜀果降于魏。

石勒：「大丈夫行事，當磊磊落落，如日月皎然，終不能如曹孟德、司馬仲達父子，欺他孤兒寡婦，狐媚以取天下也。」（《晉書·載記第五·石勒下》）

李世民曾為《晉書·宣帝紀》作史論，原文如下：「夫天地之大，黎元為本。邦國之貴，元首為先。治亂無常，興亡有運。是故五帝之上，居萬乘以為憂；三王已來，處其憂而為樂。競智力，爭利害，大小相吞，強弱相襲。逮乎魏室，三方鼎峙，幹戈不息，氛霧交飛。宣皇以天挺之姿，應期佐命，文以纘治，武以棱威。用人如在己，求賢若不及；情深阻而莫測，性寬綽而能容，和光同塵，與時舒捲，戢鱗潛翼，思屬風雲。飾忠於已詐之心，延安于將危之命。觀其雄略內斷，英猷外決，殄公孫於百日，擒孟達於盈旬，自以兵動若神，謀無再計矣。既而擁眾西舉，與諸葛相持。抑其甲兵，本無鬥志，遺其巾幗，方發憤心。杖節當門，雄圖頓屈，請戰千里，詐欲示威。且秦蜀之人，勇懦非敵，夷險之路，勞逸不同，以此爭功，其利可見。而返閉軍固壘，莫敢爭鋒，生怯實而未前，死疑虛而猶遁，良將之道，失在斯乎！文帝之世，輔翼權重，許昌同蕭何之委，崇華甚霍光之寄。當謂竭誠盡節，伊傅可齊。及明帝將終，棟樑是屬，受遺二主，佐命三朝，既承忍死之託，曾無殉生之報。天子在外，內起甲兵，陵土未乾，遽相誅戮，貞臣之體，寧若此乎！盡善之方，以斯為惑。夫征討之策，豈東智而西愚？輔佐之心，何前忠而後亂？故晉明掩面，恥欺偽以成功；石勒肆言，笑奸回以定業。古人有雲：「積善三年，知之者少，為惡一日，聞於天下。」可不謂然乎！雖自隱過當年，而終見嗤後代。亦猶竊鐘掩耳，以眾人為不聞；銳意盜金，謂市中為莫睹。故知貪于近者則遺遠，溺於利者則傷名；若不損己以益人，則當禍人而福己。順理而舉易為力，背時而動難為功。況以未成之晉基，逼有餘之魏祚？雖複道格區宇，德被蒼生，而天未啟時，寶位猶阻，非可以智競，不可以力爭，雖則慶流後昆，而身終於北面矣。」（《晉書·宣帝紀第一》）

房玄齡：「少有奇節，聰明多大略，博學洽聞，伏膺儒教。漢末大亂，常慨然有憂天下心。」「帝內忌而外寬，猜忌多權變。」（《晉書·宣帝紀第一》）

杜牧：「周有齊太公，秦有王翦，兩漢有韓信、趙充國、耿恭、虞詡、段熲，魏有司馬懿，吳有周瑜，蜀有諸葛武侯，晉有羊祜、杜西元凱，梁有韋睿，元魏有崔浩，周有韋孝寬，隋有楊素，國朝有李靖、李勣、裴行儉、郭元振。如此人者，當此一時，其所出計畫，皆考古校今，奇秘長遠，策先定於內，功後成於外。」（《注孫子序》）

司馬光：「司馬懿，少聰達，多大略。」（《資治通鑒·卷六十五》）

而宋代何去非認為司馬懿能忍耐，又有足夠的度量。不與諸葛亮正面對戰並非膽怯，而是高明的消耗敵軍之策：「仲達提秦、雍之勁卒，以不應而老其師者，豈徒然哉！將求全於一勝也。然而，孔明既死，蜀師引還，而仲達不窮追之者，蓋不虞孔明之死，其士尚飽，而軍未有變，蜀道阻而易伏，疑其偽退以誘我也。向使孔明之不死，而弊於相持，則仲達之志得矣。或者謂仲達之權詭，不足以當孔明之節制，此腐儒守經之談，不足為曉機者道也。」，評其「制其兵，出奇應變，奄忽若神，無往不殄，雖曹公有所不逮焉」。

黃道周：「司馬魏人，從討張魯。備爭江陵，請乘蜀土。言雖不從，大志已睹。關羽震樊，魏欲避許。懿請結孫，因而斬羽。孟達雖降，意猶首鼠。八日往擒，盡驚神武。諸葛出祁，以懿禦悔。利則急驅，屯則守伍。巾幗相加，亦不妄舉。食少事煩，早知其苦。五丈秋風，更輩無補。料死料生，功已足數。文懿反遼，視魚遊釜。計日攻虛，破之若取。後晉帝基，皆懿遺祜。」（《廣名將傳》）

羅貫中：「開言崇聖典，用武若通神。三國英雄士，四朝經濟臣。屯兵驅虎豹，養子得麒麟。諸葛常談羨，能回天地春！」（《戰徐塘吳魏交兵》）

毛宗崗：「今人將曹操、司馬懿並稱。及觀司馬懿臨終之語，而懿之與操則有別矣。操之事，皆懿之子為之，而懿則終其身未敢為操之事也。操之忌先主，是欲除宗室之賢者；懿之謀曹爽，是特殺宗室之不賢者。至於弒主後，害皇嗣，僭皇號，受九錫，但見之於操，而未見之於懿。故君子于懿有恕辭焉。」（《匯評三國志演義》）

蔡東藩：「從前王莽、曹操、司馬懿、劉裕諸奸雄，其險惡猶不若溫也。」（《五代史演義》）

毛澤東：「司馬懿是個了不起的人物，歷來說他壞，我看有幾手比曹操高明。」他認為曹操攻下張魯以後應該聽司馬懿和劉曄的建議進攻四川；評其「出身士族，多謀略，善權變，為魏國重臣」。曾在《三國志·陸遜傳》中評註：「此司馬懿敵孔明之智也。」（《毛澤東讀書筆記解析》）

柏楊：「就史料記載而言，真實的司馬懿，跟世人印象中的司馬懿不同，諸葛亮先生受託孤後，並沒有曹爽般的政敵，李嚴的竊弄威權，一紙命令便告解決，而曹爽先生確是將司馬懿整個排除，司馬懿對曹爽雖然不滿，但一直到244年，曹爽先生攻擊蜀漢帝國，大軍被雨困在峽谷，司馬懿仍憂慮他會失敗，勸告退軍，假使他心懷不軌，大可閉口不言，等曹爽覆滅後，由他來收拾殘局。司馬懿先生當初最大的目的，不過是反擊曹爽，奪官奪權。249年的政變，受到朝野一致愛戴，251年王淩起兵時，司馬懿不但沒有任何叛逆跡象，而且聲望正值高峰。……就司馬懿本身而言，他所受到的詬罵與詛咒，並不公平。」（《柏楊版資治通鑒》）

司馬懿在世時，在魏國威望相當高，即使文欽在其死後討伐司馬師時，在檄文中依然對司馬懿有『故相國懿，匡輔魏室，曆事忠貞』等相當多的讚譽。史書上說他做到了使『天下大悅』『天下欣賴』。晉朝初年，司馬炎有「天下無窮人」的太康之治，人民對促成三國統一的奠基者司馬還是相當推崇。甚至因司馬炎之孫司馬遹長得像司馬懿就寄予厚望。

司馬懿名聲毀敗，是從永嘉之禍以後開始的。其不肖子孫自相殘殺，帶來五胡亂華的浩劫，出身奴隸的石勒恨透司馬家。而東晉在南方，又長期被世家大族把持。晉室南渡，情況與當年蜀漢類似，以蜀漢為正統呼聲日高；東晉滅亡後，情況更明顯。到隋唐時代，民間說書戲曲日盛。唐太宗主導官修的《晉書》，以封建帝王立場更不鼓勵臣下效法。到明代《三國演義》後，火熄上方穀、見木雕魏都督喪膽等的形象也就被演義流傳民間。

呂思勉認為，司馬懿之深謀祕計，還有許多不為後人所知。而且他很為暴虐，他之政敵被殺，都是夷及三族，連已出嫁女亦不能得免，所以《晉書》作者房玄齡等人，也說他猜忌殘忍。他一生用盡深刻心計，暴虐手段，全是為一己之地位，絲毫沒有曹操匡扶漢室、平定天下之意。封建時代之道德，是公忠、正直、勇敢，是犠牲一己以利天下，司馬懿卻件件和他相反。魏武帝曹操亡歿後，司馬氏父子繼而得志，忠君愛民之心地，光明磊落之行為，全都看不見，只剩下自私自利之心地，狡詐刻毒之行為。

家世

兄弟

• 司馬朗，字伯達。

• 司馬孚，字叔達。

• 司馬馗，字季達。

• 司馬恂，字顯達。

• 司馬進，字惠達。

• 司馬通，字雅達。

• 司馬敏，字幼達。

妻妾

• 張春華（宣穆皇后）

• 張夫人

• 伏夫人

• 柏夫人

子女

兒子

• 司馬師，張春華所生。以高平陵之變封長平鄉侯。司馬懿故後襲舞陽侯，曹魏諡忠武。弟司馬昭受封晉王，追尊諡為晉景王。侄子司馬炎稱帝，追尊為世宗景皇帝。

• 司馬昭，張春華所生。曹魏時任相國，封晉王，諡文王。子司馬炎稱帝，追尊為太祖文皇帝。

• 司馬亮，字子翼（？－291年），伏夫人所生。西晉八王之亂中八王之一

• 司馬伷，字子將（227年－283年） ，伏夫人所生。晉元帝祖父

• 司馬京，字子佐（？－？），伏夫人所生

• 司馬榦，字子良（232年－311年2月26日)，張春華所生

• 司馬駿，字子臧（232年－286年），伏夫人所生

• 司馬肜，字子徽（？－302年），張夫人所生

• 司馬倫，字子彞（240－301年），柏夫人所生。後稱皇帝，年號建始。是西晉八王之亂中八王之一

女兒

• 南陽公主，張春華所生，嫁荀霬，生子荀愷。

• 高陸公主，次女，嫁杜預。

藝術形象

影視

動漫遊戲

• 真·三國無雙系列 / 無雙OROCHI系列（光榮公司開發，原瀧下毅配音，但在該系列的無雙7發售沒多久，因意外去世，所以在無雙7的帝王傳之後，改由置鮎龍太郎配音）司馬懿在遊戲中和趙雲、周瑜、呂布、貂蟬、夏侯惇為遊戲的主角。

• 三國志

• 三國演義

• 《橫山光輝三國志》（橫山光輝）中的司馬懿只在漫畫登場。

• 《火鳳燎原》（陳某）:中的司馬懿和趙雲（燎原火）同樣是故事的主角，具有狼顧之相，於董卓佔據洛陽時已經是司馬家之當家及刺客組織「殘兵」之幕後主腦，後來司馬家遭許定血洗後投靠曹操以報家族滅門之仇，曾以「反曹」之名合作於適當時背叛及殺害使劉竉、呂布、袁方、郭援和左慈敗亡，於赤壁之戰時與諸葛亮有計謀間諜往來，在華容道後和諸葛亮「互相協助」。

• 《蒼天航路》（王欣太）中的司馬懿在故事後期登場，曹丕四友之一，頭能一百八十度轉動，曹操看此狼顧之相相當吃驚。

• 《王者榮耀》中的司馬懿職業是一名刺客/法師

• 《Fate/Grand Order》中憑依在萊涅絲而成為英靈，職階為Rider，寶具「混元一陣」。

注釋