Sima Yi

Sima Yi (179 – September 7, 251) was a general and politician of the state of cao wei during the three kingdoms era of Chinese history. He is perhaps best known for defending Wei from Zhuge Liang's Northern Expeditions. His success and subsequent rise in prominence paved the way for his grandson Sima Yan's founding of the jin dynasty, which would eventually bring an end to the three kingdoms era. In 265 after the jin dynasty was established, Sima Yi was posthumously honored as Emperor Xuan of Jin with the temple name of Gaozu.

Early life

Sima Yi was one of eight brothers, all of whom were famous due to their lineage. Each of them had a Chinese style name ending with the character Da (達). Because of this, the brothers were known collectively as the "Eight Da of Sima" (司馬八達). This was a term of respect, as other groups of eight talented administrators in previous eras had been referred to in this way. His family resided in Luoyang when Dong Zhuo occupied the city, destroyed it, and moved the capital to Chang'an. Sima Yi's elder brother, Sima Lang led the family to their ancestral home in the Wen district (温縣), and then, correctly predicting that it would become a battlefield, moved them again to Liyang (黎陽). In 194, as Cao Cao did battle with Lü Bu, Sima Yi accompanied his family back to Wen district.

Service under Cao Cao

Accounts on how Sima joined the service of Cao differ, but he accepted his first position in Cao's camp at the age of 30. According to the Book of Jin, Sima believed that the han dynasty would soon come to an end, and felt no motivation to join Cao, which had already taken control of the Han seat of government. He refused Cao's requests to serve, saying that he was suffering from a disease. Cao did not believe Sima's excuse, and sent agents to check on him at night. Sima, knowing this in advance, stayed in bed all night and did not move. In 208, Cao became Imperial Chancellor and ordered Sima to serve him, saying "If he dallies, arrest him." Afraid of what would befall him, Sima finally accepted the position of Wenxueyuan (文学掾).

according to Weilüe, Cao Hong, Cao Cao's younger cousin, requested the presence of Sima in order to start a friendship with the latter, who did not have a very high opinion of Cao Hong and feigned illness by carrying a cane in order to avoid meeting him. Cao Hong went to Cao Cao in anger and told him what had happened, after which Cao Cao directly requested the presence of Sima. Only then did Sima officially enter Cao Cao's service.

In the Chancellor's service, he rose through the ranks of Dongcaoyuan (東曹掾; in charge of bringing officials into service), Zhubo (主簿; an administrative position), and Sima (司馬; position in charge of aids and advisors). In 215, when Cao Cao defeated Zhang Lu and forced him to surrender, Sima advised that Cao Cao continue to advance south into Yi Province, since Liu Bei had still not stabilized his control of that area. However, Cao Cao did not listen to his advice. Sima was among other advisors who urged for the implementation of the tuntian system and for Cao Cao to take the position of Prince of Wei.

Service under Cao Pi

Even before Cao Cao's death, Sima Yi was close to his successor, Cao Pi. When Cao Pi was designated Crown Prince of Wei in 216, Sima was made his secretary. When Cao Cao wavered on choosing between Cao Pi and his younger brother Cao Zhi, Sima was believed to be among those who backed Cao Pi and helped him secure the succession. Due to the fact Sima had been a long time friend of Cao Pi since the latter held the position of General of the Household, he became greatly trusted when the latter ascended the throne. He was also involved in Cao Zhi's demotion and removal from politics.

In 225, Cao Pi advanced against Sun Quan's Wu, and entrusted Sima Yi with command over the capital in his absence. He compared Sima Yi to Xiao He, whose quiet contributions behind the battle lines earned him much praise. Upon returning from the military expedition, Cao Pi once again praised his servant, saying "As I did battle in the East, you stayed in the capital and guarded our kingdom against Shu in the West. When I go to battle in the West against Shu, I'll entrust you with defense against Wu in the East." Sima Yi was soon given the post of Lushang Shushi (録尚書事), which at that time held the same real
power and responsibilities as Imperial Chancellor. Sima Yi's position within Wei was now all but unassailable.

Service under Cao Rui

In 226, as Cao Pi lay on his deathbed, he entrusted his successor Cao Rui to the care of Sima Yi, Cao Zhen, and Chen Qun. When Cao Rui became Emperor of Wei, he trusted Sima Yi greatly and appointed him Piaoqi General (骠骑大将军) and military commander of Yuzhou and Jingzhou (督荊豫二州諸軍事) and was placed on the border between Wei and Wu to defend against Sun Quan's forces.

Battle of Xincheng

In 220, when Meng Da surrendered to Wei and Cao Pi entrusted him as Administrator of Xincheng. Sima Yi did not trust him, and argued his case to Cao Pi, but his advice was not taken. In 227, Meng Da began making overtures to Wu and Shu, promising to turn against Wei when an opportunity presented itself. He was very slow to move in response to Zhuge Liang's urgings, however, and Zhuge Liang attempted to spur him into action by leaking Meng Da's rebellious intentions to Shen Yi, the administrator of Weixing (魏興). When Meng Da learned that his plans had been discovered, he began raising troops in preparation for action.

Fearing quick action by Meng Da, Sima Yi sent him a letter saying "Long ago, you surrendered to our kingdom, and we put you in charge of the defense of our borders against Shu. The people of Shu are foolish, and still hate you for not coming to Guan Yu's assistance. Kongming is the same, and he has been looking for a way to destroy you. As you probably suspect, the news of your rebellion is only his plot." Meng Da now believed that he was safe, and did not rush his preparations. He believed that Sima Yi, posted on the border of Wei and Wu, would require a month to go to Cao Rui and request permission to raise troops, then to reach Xincheng. However, Sima Yi was already on his way and reached Xincheng in 8 days, quickly defeating the unprepared Meng Da, who was killed in the battle. This action contributed indirectly to the success at the Battle of Jieting and earned Sima Yi much praise.

Zhuge Liang's Northern Expeditions

When Cao Zhen, who had been leading the defense against Zhuge Liang's Northern expeditions died in 231, Sima Yi took his position in command, and faced Zhuge Liang's armies for the first time in battle. Sima Yi kept his armies safe in fortifications, his strategy being to wait out the Shu armies who had a very difficult time keeping their armies supplied with provisions. He did not attempt to do battle with Zhuge Liang whatsoever, and was mocked by his own subordinates, who claimed he was the laughing stock of the world. Unable to resist doing battle any longer, he allowed his generals to attack Shu's positions, but they were badly defeated and suffered losses including 3000 soldiers, 5000 suits of iron armor, and 3000 crossbows. When Zhuge Liang finally did retreat, Sima Yi ordered Zhang He to pursue, who was ambushed and killed.

The second battle between Sima Yi and Zhuge Liang was in 234. Cao Rui again identified Shu's problem being keeping their army supplied, and ordered Sima Yi to keep his armies fortified and wait the enemy out. The two armies faced each other at Wuzhang Plains. Although being challenged many times by Zhuge Liang, Sima Yi did not send his armies to attack. To provoke Sima Yi, Zhuge Liang sent women's clothes to him, suggesting that he was a woman for not daring to attack. The Wei officers were enraged by this, but Sima Yi would not be provoked. To appease his officers, Sima Yi asked the Wei Emperor Cao Rui for permission to engage the Shu forces. Cao Rui, understanding the situation, sent his advisor Xin Pi to Sima Yi telling the Wei forces to be patient. In an attempt to engage the Wei forces, Zhuge Liang sent Sima Yi an emissary urging him to battle. Sima Yi, however, would not discuss military matters with the emissary, instead inquired about Zhuge Liang's tasks. The emissary replied that Zhuge Liang personally manages matters both big and small in the military, from military tactics to meals for the night, but he consumes very little. Sima Yi then told an aide that Zhuge Liang would not last long.

Following Zhuge Liang's death, the Shu forces quietly withdrew from their camps while keeping Zhuge Liang's death a secret. Sima Yi, convinced by the locals that Zhuge Liang had died, gave chase to the retreating Shu forces. Jiang Wei then had Yang Yi turn around and pretend to strike. Seeing this, Sima Yi feared that Zhuge Liang only pretended he was dead to lure him out, and immediately retreated. Word that Sima Yi fled from the already dead Zhuge Liang spread, spawning a popular saying, "A dead Zhuge scares away a living Zhongda" (死諸葛嚇走活仲達), referring to Sima Yi's courtesy name. When Sima Yi heard of such ridicule, he laughingly responded, "I can predict the living, but not the dead." (帝聞而笑曰:「吾便料生,不便料死故也。」)

Expedition against Gongsun Yuan

After Guanqiu Jian had failed to defeat the forces of Gongsun Yuan in Liaodong, and Gongsun Yuan had declared himself Prince of Yan, Cao Rui put Sima Yi in charge of the next expedition against him. Sima Yi defeated Gongsun Yuan twice on the field of battle, and forced him to retreat to Xiangping (襄平), where he prepared for siege. Long rains brought a temporary break from the fighting, but as soon as they lifted, Sima Yi launched an all out attack. Gongsun Yuan and his sons were killed while attempting to flee

Service under Cao Fang and coup d'état

As Cao Rui lay on his deathbed, he had doubts about Sima Yi, and initially planned to exclude him from the regency of his successor Cao Fang. He wanted to entrust Cao Fang to his uncle Cao Yu (曹宇), to serve as the lead regent, along with Xiahou Xian (夏侯獻), Cao Shuang, Cao Zhao (曹肇), and Qin Lang (秦朗). However, his trusted officials Liu Fang (劉放) and Sun Zi (孫資) were unfriendly with Xiahou and Cao Zhao and were apprehensive about their becoming regents, and managed to persuade him to make Cao Shuang (with whom they were friendly) and Sima Yi (who was then with his troops at Ji (汲縣, in modern Xinxiang, Henan , and to who Liu Fang and Sun Zi were close to) regents instead. Cao Yu, Cao Zhao, and Qin were excluded from the regency.

Initially, Cao Shuang and Sima Yi shared power, but Cao Shuang quickly used a number of political maneuvers to honor Sima with honorific titles including Grand Tutor while stripping his actual power. Cao Shuang then made all important decisions and stopped consulting Sima. Quickly, Cao's associates, including Deng Yang (鄧颺), Li Sheng (李勝), He Yan (何晏), and Ding Mi (丁謐), who were known for their talents but lack of wisdom, all became powerful, and they excluded other officials who would not associate with them from positions of power. Sima was still given military authority (including command in repelling a major Eastern Wu attack in 241), but no real authority on governance.

Incident at Gaoping Tomb

In 244, Cao Shuang, who wanted to garner for himself a military reputation as well, made a major attack against Shu Han's major border city of Hanzhong (in modern Hanzhong, Shaanxi ), without careful logistics planning. The battles themselves were inconclusive, but after cao wei forces ran out of food supplies, Cao Shuang was forced to withdraw at great loss of life. Despite his failure on the battlefield, however, Cao Shuang held onto power firmly. In 247, Sima, upset at his actual powerlessness, claimed that he was ill and retired from government service. Cao Shuang sent Li Sheng to determine whether or not Sima Yi was truly ill, and Sima Yi deceived him by acting senile in his presence.

In 249, Sima made his move. While Cao Fang and Cao Shuang were outside the capital on an official visit to Cao Rui's tomb, Sima, with support from a number of anti-Cao Shuang officials, claiming to have an order from Empress Dowager Guo to do so, closed all city gates of Luoyang and submitted a report to Cao Fang, accusing Cao Shuang of dominating and corrupting the government and demanding that Cao Shuang and his brothers be deposed. Cao Shuang was stricken by panic and did not know how to react, and even though his senior advisor Huan Fan recommended that he take Cao Fang to the secondary capital Xuchang and then resist Sima with his troops, Cao chose to surrender his troops and powers, under promise by Sima that he would still be able to maintain his wealth. However, Sima soon reneged on the promise and had Cao Shuang and his associates, as well as their clans, executed on charges of treason. Although not a popular theory, some believe this intention of betrayal to the Cao line stretched as far back as Sima Yi's days of serving the original Wei ruler, Cao Cao. This is because Cao Cao once told Cao Pi that Sima Yi was hiding an ambition, and would not die merely serving another.

After Sima Yi's takeover, he carefully but inexorably removed people who were actual or potential threats to his authority. Yet, at the same time, he strived to distance himself from the patterns followed by the man his actions seemed to mirror most - Cao Cao; when Cao Fang offered him the nine bestowments, he strenuously refused them, only accepting them after more than three offers. The 18-year-old Cao Fang left himself in a vulnerable position by going so far as to grant one of his followers such influence; Sima, however, had the support of the people by removing corruption and inefficiency that characterized Cao Shuang's regency and promoting a number of honest officials. He was offered the title of Imperial Chancellor, but refused.

Wang Ling's case

In 249, the powerful general Wang Ling, who was in charge of the key southeastern city of Shouchun (壽春, in modern Luan , Anhui ) began to plan a revolt against Sima's hold on power, in association with Cao Biao (曹彪), the Prince of Chu and a son of Cao Cao (whom he planned to replace Cao Fang with as emperor). In 251, Wang was ready to carry out his plans when his associates Huang Hua (黃華) and Yang Hong (楊弘) leaked the plan to Sima. Sima quickly advanced east before Wang could be ready and promised to pardon him. Wang knew that he was not ready to resist, so he submitted, but Sima again reneged on his promise and forced Wang and Cao Biao to commit suicide. Wang's clan and the clans of his associates were all slaughtered. Having secured his family's control of cao wei, Sima Yi died in 251, succeeded by his son Sima Shi.


After the fall of the western jin dynasty, the belief began to shift from the popular ideal that Wei was the rightful successor to the Han toward a sympathetic view of Shu Han. Before this change, Sima Yi was seen as a righteous figure in the Book of Jin and was practically deified. Afterwards, Sima Yi began to be vilified; a view which was epitomized in the classic novel Romance of the three kingdoms. In the novel, Sima Yi was portrayed as the dedicated servant of Cao Cao, obsessed with his ideals even to the point of honing his example of usurping power against a weak ruler and using it to bring down Cao Cao's own descendants. In terms of history, many of the accounts are either contradicted or simply do not exist and were most likely borrowed from either the elements of Luo Guanzhong's imagination or from folk tales that had been passed down through the ages.

As Sima Yi's contributions toward cao wei are substantial, the debate of his legacy lies within what motivated his actions. A debate, that has continued to this day and will most likely never be resolved, as to whether Sima Yi was acting in a benevolent way, such as Huo Guang did during the han dynasty, or whether he was acting out of pure ambition, comparable to Wang Mang's short-lived xin dynasty. However, he died only a few years after forcibly regaining his power from Cao Shuang, leaving no definitive answer to his intentions for future generations.


One legend about Sima Yi is that he could turn his head 180° around on his neck to look backwards without turning his body. This characteristic was called "the turning-back of the wolf" (狼顧) supposedly based on the fact that wolves are cautious and aware of everything going on around them as though they had eyes in the back of their heads. It is said that Cao Cao heard this rumor and wanted to test it for himself. According to the legend, he came up behind Sima Yi and called out his name, and indeed his head did turn completely around. According to the Book of Jin, when Cao Cao saw this he grew cautious of Sima Yi, saying "This man is hiding great ambition". Cao Pi would later say of Sima Yi "This man probably has no intention of ending his life as a mere servant".

Personal information


Sima Jun (司馬鈞), great-great-grandfather, served as General Who Conquers the West during the reign of Emperor An of Han

Sima Liang (司馬量), great-grandfather, served as Prefect of Yuzhang

Sima Jun, grandfather, served as Prefect of Yingchuan


Sima Fang, served as Intendant of Capital City


Sima Lang, older brother, served cao wei

Sima Fu, younger brother, served cao wei

Sima Kui (司馬馗), younger brother

Sima Xun (司馬恂), younger brother

Sima Jin (司馬進), younger brother

Sima Tong (司馬通), younger brother

Sima Min (司馬敏), younger brother


Zhang Chunhua, bore Sima Shi, Sima Zhao, Sima Gan and Princess Nanyang, posthumously honoured as Empress Xuanmu

Concubine Fu (伏貴妃), bore Sima Liang, Sima Zhou, Sima Jing and Sima Jun

Lady Zhang (張夫人), bore Sima Rong

Lady Bai (柏夫人), bore Sima Lun



Sima Shi, regent of cao wei, posthumously honoured as Emperor Jing of Jin

Sima Zhao, regent of cao wei, granted title Prince of Jin, posthumously honoured as Emperor Wen of Jin. Fathered Sima Yan.

Sima Gan (司馬榦), Prince of Pingyuan

Sima Liang, Prince Wencheng of Runan, was involved in the War of the Eight Princes

Sima Zhou, Prince Wu of Langya, grandfather of Emperor Yuan of Jin

Sima Jing (司馬京), Marquis of Qinghuiting

Sima Jun (司馬駿), Prince Wu of Fufeng

Sima Rong (司馬肜), Prince Xiao of Liang

Sima Lun, Prince of Zhao, was involved in the War of the Eight Princes


Princess Nanyang (南陽公主), personal name unknown

Princess Gaoling (高陸公主), personal name unknown

Last update 01-04-2012

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