In Chinese history, the Three Kingdoms period is a high-profile era, Cao Wei, Shu Han, and Eastern Wu are three kingdoms, and the relationship between Cao Wei and Shu Han is even more complicated, especially after the death of Zhuge Liang, why Sima Yi did not dare to attack Shu has become a controversial topic in history.
First, let's look at Zhuge Liang's lifetime. Zhuge Liang, with his superior political talent and military wisdom, kept Shu Han on the offensive and Cao Wei on the defensive. Despite Sima Yi's outstanding abilities, he was not fully trusted and given enough power under Cao Zhen's leadership. Cao Zhen led his army to attack Shu Han, but encountered continuous heavy rain, coupled with opposition from the government and the opposition, which eventually led to the failure of the plan to cut down Shu. After Cao Zhen's death, Sima Yi gradually gained military power in the west, but Cao Wei still faced internal and external difficulties.
Second, after Zhuge Liang's death, although the Shu Han regime faced a change in leadership, Cao Wei did not immediately take the opportunity to attack. Cao Rui, the emperor of Cao Wei, considered that the war with Shu Han for many years had consumed a lot of resources, and after Zhuge Liang's death, Shu Han's activities also decreased, and the border was relatively peaceful. At the same time, the terrain of Shu Han was dangerous, easy to defend and difficult to attack, and it was difficult to transport grain and grass, coupled with the fact that Sima Yi's position in the court was not solid, Cao Rui was worried that Sima Yi would take the opportunity to stand on his own, so he did not attack easily.
Third, Cao Rui did not fully trust Sima Yi and was worried that he would usurp the throne. Cao Rui was reluctant to risk Sima Yi leading his army to attack Shu Han in the face of political instability, lest Sima Yi take the opportunity to seek greater power and thus endanger the stability of Cao Wei's rule.
As for the power struggle between Cao Shuang and Sima Yi, Cao Wei fell into chaos internally, and Sima Yi was busy dealing with internal affairs, and it was difficult for him to deal with external wars. Therefore, until Sima Yi grasped the power of the court, he had no time to take care of the attack on Shu Han.
To sum up, the main reasons why Sima Yi did not dare to attack Shu include: political instability, geographical and resource factors between Cao Wei and Shu Han, and Cao Rui's distrust of Sima Yi. This period of history also reflects the complexity of the political and military situation at that time, as well as the delicate relationship between the various forces.