(Cao Cao)
"To aim high" means to have ambition, not a person living in poverty. "The wolf cares about the phase" means that when the wolf walks forward, he always looks left and right and looks back. It means to be quite cautious and do things in a watertight way. A person who aims high and does things in a watertight way is actually quite dangerous. Since it is so dangerous, why didn't Cao Cao kill Sima Yi and leave a clear sky for his descendants?
First, although Cao Cao saw that Sima Yi was a dangerous man, he didn't expect Sima Yi to threaten his descendants. At that time, although Cao Cao was already the actual leader of the northern military group, he was not actually an emperor. He is bent on making his son a successful emperor. In other words, his focus at this time is on those who can pose a threat to his son as emperor. Who will make irresponsible remarks about his son being emperor, even a military threat? Instead of his son becoming emperor, or even his grandson becoming emperor, who will take over the country from his Cao family? Although Sima Yi was ambitious, he was only an aide to his son Cao Pi at that time, and he did not belong to the person who prevented his son from ascending to the throne. So Cao Cao didn't think Sima Yi would be much of a threat.
(Sima Yi)
Second, Sima Yi seems to be very loyal to his son Cao Pi. Cao Cao is considering whether to let Cao Pi succeed or Cao Zhi succeed. Originally, he likes Cao Zhi best, and he is also trying to cultivate Cao Zhi. But Cao Zhi is really flashy and useless. So in the end, he changed his mind and trained xelloss instead. When he focused on cultivating Cao Pi, he considered who would pose a threat to Cao Pi as emperor. Obviously, Yang Xiu is a threat. Because Yang Xiu belongs to Cao Zhi, and he is not a contented man. If he exists all the time, he will definitely encourage Cao Zhi to beat Cao Pi. In this way, his two sons will have civil strife. Therefore, he will never tolerate Yang Xiu. Sima Yi is a man who is dedicated to helping Cao Pi. He didn't encourage xelloss to engage in civil strife like Yang Xiu, so Cao Cao had no reason to kill him.
Third, Cao Cao is a man who loves talents and generally does not kill talents casually. In the Cao Cao era, although it was actually a "filial piety and honest system", the gate was actually very strict. Generally speaking, only gentry can be an official, and the possibility of lower-level intellectuals being an official is very small. Cao Cao attached great importance to the talents in the world, and put forward the slogan of "meritocracy is the promotion", and gained a large number of talents regardless of gate and gate. In fact, Sima Yi didn't want to follow Cao Cao at first. When Cao Cao summoned him, he pretended to be ill. Cao Cao gave the death order in the name of the Prime Minister. He was afraid of death and had to go. So Cao Cao asked a man to kill him if he didn't come. Of course, Cao Cao did kill many intellectuals, including Kong Rong and Mi Fei. But he actually tolerated them many times, and there was really no way to kill them. Including his killing of Yang Xiu, was tolerated many times. It should also be noted that after the death of Cao Cao, his "meritocracy" was not inherited by his son. His son Cao Pi re-established a set of nine-product system, which is almost a replica of the gate valve system.
(Cao pi)
Fourth, Cao Cao has actually suppressed Sima Yi many times to prevent him from becoming bigger. For example, in 2 15, when Sima Yi led an army to crusade against Zhang Lu, he suggested to Cao Cao to directly kill Liu Bei, who had already won Yizhou, to prevent Liu Bei from becoming bigger. This is actually a good suggestion, but Cao Cao didn't listen to him. Later, when we fought again, we didn't take Sima Yi with us. However, Cao Pi attached great importance to Sima Yi, pleaded for Sima Yi many times before Cao Cao, and adopted Sima Yi's tactics, which made great achievements. Cao Cao also told xelloss to beware of Sima Yi, but xelloss always protected Sima Yi. In this case, Cao Cao wanted to make Xelloss bigger and had to do it.
In a word, Sima Yi finally developed. It can only be said that Cao Cao's descendants were too weak to let Sima Yi seize the opportunity. If Cao Cao's descendants are as powerful as Cao Cao, Sima Yi's scheming will only be a flash in the pan. It's really no wonder that Cao Cao.