During the Three Kingdoms period, strategists can be described as a resource that the major princes competed for, talented strategists can be compared with thousands of armies and horses, and a single plan can make the enemy pay a heavy price. It can be said that the dispute between the three countries is not only a struggle for the strength of the army, but also a struggle of wisdom. Yuan Shao's army was several times that of Cao Cao's army, but there were a few more strategists in Cao Cao's military camp than Yuan Shao, especially high-end talents, Cao Cao had an absolute advantage, and with the assistance of Xun Yu, Guo Jia and others, Cao Cao unified the north with fewer victories.
In terms of managing the strategists, whether it was Cao Cao or Liu Bei, they all had a hand on these strategists. The king used gold and silver jewelry, official positions, and ideals to inspire these counselors, and even to impress other courtiers, so that the warriors had absolute loyalty to their descendants, so the counselors generally did not rebel. However, there was a strategist in Cao Cao's military camp who became a big winner in the late Three Kingdoms period, and this strategist was Sima Yi. In the late Three Kingdoms period, when Cao Cao and Liu Bei died one after another, the Three Kingdoms were left with a battle of wits between Sima Yi and Kong Ming, and Zhuge Liang repeatedly sent troops to the Northern Expedition, but they failed to take advantage of Sima Yi.
Sima Yi was originally the son of the Han Dynasty general Zhengxi, but the Han Dynasty had exhausted its strength, and Sima Yi liked to travel and study, and he intersected with hermits everywhere, and from then on Sima Yi's knowledge became more extensive. Sima Yi was known as a child prodigy since he was a child, and in his twenties, Cao Cao sent someone to invite him to join Cao's army, but Sima Yi pretended to be ill and escaped. Later, Cao Cao became a chancellor, and remembered Sima Yi as a talent, so he invited Sima Yi again, and also issued a death order, this time Sima Yi did not dare to disobey, and could only obediently return to Xuchang with his envoys. Sima Yi later became Cao Chong's teacher, and he was even more instrumental in Cao Cao's military.
After Cao Chong's death, Sima Yi had a very good relationship with Cao Pi, and Sima Yi became Cao Pi's guest. Later, Cao Cao sent troops to attack Zhang Lu, and Sima Yi also went with him, during the crusade, Sima Yi showed outstanding military ability, he repeatedly suggested that Cao Cao hoard grain in the rear, Cao Cao adopted his advice, and soon after Sima Yi was promoted to Sima Yi. Later, Guan Yu sent an army to attack Fancheng, and Sima Yi suggested that Sun Quan send troops to attack Jingzhou, and sure enough, Lü Meng led his troops to attack Jingzhou, and Guan Yu was already about to capture Fancheng, but the rear could only withdraw after the rear was not secure.
Guan Yu was eventually killed by Eastern Wu, a battle that angered Liu Bei and broke Sun Liu's alliance, buying time for cao Wei's stability later. Liu Bei later attacked Eastern Wu, eventually depleting the entire strength of the Shu army and directly influencing Zhuge Liang's Northern Expedition. Sima Yi had been assisting Cao Pi since Cao Cao's death, and although he had made great achievements for Cao Cao's army, Cao Pi remembered Cao Cao's admonition and never let Sima Yi hold an important official position in the imperial court. While Sima Yi was resisting Zhuge Liang's Northern Expeditionary Army, he gradually established his prestige in the Cao army, and although he could not be promoted or reused, he was already a figure in the eyes of the general. Later, Cao Pi died, and Sima Yi became the leader of Cao's army.
Cao Shuang learned that Sima Yi was harboring disloyalty, and originally he wanted to force Sima Yi to disarm and return to the field, but Sima Yi made a move against him, and finally Cao Shuang was trampled under Sima Yi's feet, and from then on, the Cao family's world was taken over by the Sima family. Although Sima Yi did not directly usurp Wei's independence, it was an ironclad fact that the Sima family controlled the imperial government during his lifetime. After Sima Yi's death, Sima Yan ascended the throne as emperor and posthumously honored him as Emperor Xuan, so he was also considered the emperor of a dynasty.