What is history: it is the echo of the past to the future, the reflection of the future on the past. - Hugo
China's feudal society lasted for nearly two thousand years. The change of dynasties has not stopped. Most of these dynastic changes took the "Tangwu Revolution" as a model to overthrow the previous generation through war. The beautiful "Zen concession system" in ancient times was not the mainstream in the future.
However, it is interesting that there are not many people who use Zen to make the emperor, but they have caused a lot of trouble. Cao Pi and Sima Yan, who lived in very similar eras, were both emperors of Zen, but one was called "Dai Han" and the other was accused of "usurping Wei", and their reputations were far apart.

I. The Causes and Consequences of Cao Pi's Zen
Cao Pi's zen is not so much that he himself is called emperor, but rather that it is a joint victory between Cao Cao and Cao Pi. "Holding the Son of Heaven to order the princes" has long been a well-known image of Cao Cao's women and children. He also did have the strength to force Emperor Xian of Han to sit on him. However, due to the promise made in his early years not to seize the throne, the threat of other separatist forces, and the opposition of some Han courtiers, Cao Cao eventually only became the "uncrowned king" of Jiajiuxi.
As Cao Cao's heir, Cao Pi inherited Cao Cao's political capital and also had the hard power to seize the throne. In fact, after Cao Cao's death, he began to persecute Emperor Xian of Han for the throne. And what Cao Pi did better than Cao Cao was that he worked hard to win over all the forces he could.
Within Cao Wei, Cao Pi first gained the support of traditional Confucian forces as the eldest son. Mao Jiu, Cui Yan, and others either admonished Cao Cao with the calamity of ancient childhoodhood, or repeatedly boasted about Cao Pi to Cao Cao. After Cao Pi intended to replace the Han Dynasty, these traditional Confucians turned to preaching the "Mandate of Heaven" of Cao Pi's Han Dynasty, and contributed an important force for Cao Pi to get rid of the usurpation of the throne.
Second, Cao Pi co-opted many of Cao Cao's old subordinates. Jia Xu, Xun You, and Xun Yu, Cao Cao's confidants, were all Cao Pi's guests. Later, Jia Xu even directly sided with Cao Pi and advised Cao Cao to make Cao Pi crown prince.
At the same time, Cao Pi also attached great importance to the control of Cao Wei's military power. Xiahou Shi, the in-law who fought with Cao Cao in the world, was the core of Cao Wei's military and a supporter of Cao Pi. Xiahou Yuan's two sons, Xiahou He and Xiahou Shang, were so close to Cao Pi that they reached the point of "friendship of cloth clothes".
As for the courtiers who were originally loyal to the Han Dynasty, Cao Pi also took many measures to win him over. Hua Xin and Wang Lang, who represented the traditional family door valves, were granted the high positions of Situ and Sikong by Cao Pi respectively. The Han Dynasty Shangshu Chen Jiao and Chen Qun were also co-opted by Cao Pi and later became Cao Wei's Shangshu.
It can be said that under the overall situation that Emperor Xiandi of Han had not mastered the real power for a day and the overthrow of the Han Dynasty was irreversible, Cao Pi was strong enough to be Zen and "the people's will". And before he really accepted the Zen throne, he had already staged three times in the court that Emperor Xian of Han wanted to take the Zen throne but Cao Pi politely refused. This made the change from the Eastern Han Dynasty to Cao Wei completed by Cao Pi's hand reach an unprecedented stability, and also created favorable conditions for Cao Pi's rule after the Han Dynasty.
Second, the causes and consequences of Sima Yan's zen
In contrast, Sima Yan. Although his acceptance of Cao Yi's Zen position was also a strength support, his zen foundation was far inferior to that of Cao Pi more than forty years ago.
Sima Yan's political capital is the capital of the infamous Sima clan. From the scheming Sima Yi onwards, Sima Shi was accused of wolf ambitions. In the generation of Sima Yan's father, Sima Zhao, "Sima Zhao's heart is known to everyone" is even more widespread than "blackmailing the son of heaven to order the princes". This made it impossible for Sima Shi to forget the fact that they had usurped power no matter how much they guided or even beautified it.
At the same time, Sima Yan's personal ability was not as good as Cao Pi's. In the matter of winning people's hearts, Sima Yan can only be regarded as unsatisfactory. In terms of government that can more influence public opinion, Sima Yan also made serious mistakes that are difficult for the people to forgive.
Iii. The difference between Sima Yan and Cao Pi's political and reputation
As far as the Zen position is concerned, Sima Yan and Cao Pi actually have too many similarities. The experience of the two becoming heirs is even the same. However, after being made emperor by Zen, Sima Yan and Cao Pi embarked on two completely different paths: Emperor Xuan and Emperor Ming.
As we mentioned earlier, Cao Pi gained the support of the Humerus of Han Ting and Cao Wei. After becoming emperor, Cao Pi also implemented the Nine Pins Official Law, which encircled the scattered people in the world and attacked foreign relatives and eunuchs. In particular, the prohibition of the harem and the dictatorship of eunuchs, allowing Cao Wei to change the ills of the Han Dynasty for a hundred years, was of great significance to future generations.
At the same time, Cao Pi implemented a policy of resting with the people, directly benefiting the people. This move combined with Cao Pi's emphasis on talents and the implementation of the Nine Pins Official's Law, which made the farmers in the field and the sergeant in the house praise him a lot. As a result, compared with the previous Han Xiandi, who had almost no sense of existence, Cao Pi undoubtedly became a beloved monarch who was in the limelight in the short term.
However, Sima Yan, although in the early stage of Zen, was still able to eat and drink at night, exerted great efforts to govern, and implemented some strategies to benefit the country and the people. However, after the suppression of Eastern Wu and the complete unification of the world, he began to drive straight into the "lane" of the Emperor of Darkness, extravagant and fainting to the extreme. In the future, wuhu chaohua, which made the middle primordial spirit ruined, planted the first seeds in his rule.
Therefore, even if we only look at the achievements of Sima Yan and Cao Pi, we can make a very clear judgment: Cao Pi is loved by people, and Sima Yan is hated by people. Therefore, even if they were all called emperors by Zen, Sima Yan, who was born from the Sima clan, was ultimately a "usurper of Wei", while Cao Pi was a "Dai Han" who obeyed the Mandate of Heaven.