Sima Yi (179 – 251 AD), with styled Zhongda was a great strategist and statesman of Wei Kingdom in Three Kingdom Period. Based on his power, his son Sima Zhao conquered Shu Kingdom and was titled as King of Jin, and his grandson Sima Yan dethroned emperor of Wei and was able to finally establish Jin Dynasty, after a long wait.

Sima Yi descended from the famous historian Sima Qian, author of “Shiji” (“Historical Records”). He was one of 8 brothers, all of whom were famous due to their lineage. Each of them had a Chinese style name ending with the character Da. So the brothers were known collectively as the "Sima Eight Das".
Sima Yi began his career as Secretary of Literature under Lord Cao Cao after the pacification of the north. Sima Yi’s first military assigned was against Zhang Lu in Hanzhong. Sima Yi’s strategies were a success and Cao Cao was greatly impressed

Cao Pi, Cao Cao’s son and the first emperor of Wei Kingdom had a great trust in Sima Yi, appointing him Chief Secretary and titled him Lord of Hejin Precinct. Later Sima Yi

was appointed as Senior Assistant to the Prime Minister.
In 220 AD, after the death of Lord Cao, his son Cao Pi took his place and wanted to force Emperor Xian to abdicate the throne. When the letter of Emperor Xian regarding the abdication came, Sima Yi advised Cao Pi to reject the first offer to silence the murmurings of the people. Cao Pi took this advice and rejected the seal of rule three times before becoming the Wei Emperor.
When Cao Pi’s son Cao Rui succeeded the throne, Sima Yi was appointed as Great General of the Flying Cavalry, and was in charge of defending Xiliang district. Sima Yi’s talents as military strategist and his able leadership prevented Zhuge Liang, the chief minister of Shu Kingdom from gaining the upper hand in the battles between Wei and Shu. In 238 AD, Sima Yi was promoted to Grand Commandant.
When Cao Fang succeeded the throne, Sima Yi was appointed as Grand Preceptor. But he lost the control of the military to the regent of the Emperor, Cao Shuang, the son of Cao Zhen.
In 249 AD, Sima Yi decided that the reign of the weak Wei Emperors needed to stop and pulled off a ‘Coup d’etat’. In the process, Cao Shuang and his supporters were put to death.
Resultantly, Sima Yi was appointed as Prime Minister and received the Nine Dignities from Cao Fang. Sima Yi placed his sons Zhao and Shi in high positions and took away power or killed anyone who still supported the Cao Family. Sima Yi died of natural causes at the age of seventy-two in 251 AD.