At the end of the Eastern Jin Dynasty, Emperor Sima Dezong of the Jin Dynasty ascended the throne, and he was known throughout Chinese history for his lack of intelligence. He could not even tell the difference between summer and winter, did not know whether he was full, could hardly take care of himself in life, and lacked the ability to handle government affairs. During Sima Dezong's reign, the control of imperial government completely fell into the hands of the ministers. In this case, the power of the imperial court was naturally controlled by the powerful ministers, and the local families also began to become active.
In the end, Huan Xuan of the Huan family couldn't help but ask Xingshi about his guilt and plotted to usurp the throne and ascend the throne. In turbulent times, the Northern general Liu Yu rose to prominence, successfully quelled the multi-route rebellion, took control of the Eastern Jin Dynasty, and re-supported Sima Dezong, who was unable to govern. At this moment, Liu Yu has basically mastered the whole country, and both inside and outside the Eastern Jin Dynasty already know that it is only a matter of time before Liu Yu is about to become emperor.
Sima Dezong's younger brother, Sima Dewen, had been by his side, fearing for his safety. Liu Yu, on the other hand, was planning behind his back, believing in a folk proverb: "After Changming there are still two emperors", in which Changming refers to Sima Dezong's father, Sima Yao, the emperor of Jin Xiaowu. Liu Yu pondered that the Eastern Jin Dynasty must have another emperor to complete the replacement. However, he waited impatiently, so he quietly laid out a plan.
Coincidentally, Sima Dewen fell ill, and he left the palace to return to his mansion to recuperate. With no one to take care of him, Liu Yu hatched a conspiracy to strangle Sima Dezong alive. According to the Southern History, Sima Dezong was even poisoned by Wang Shaozhi, a Zhongshu attendant. After that, Liu Yu asked Sima Dewen to continue as emperor in order to reach the number of "two emperors after Changming", and then impatiently arranged for Sima Dewen to "Zen relinquish" the throne to himself.
It is worth noting that Liu Yu's action set a dangerous precedent. Prior to this, no Zen emperor had been killed and would have been able to live peacefully after his abdication. However, Liu Yu's actions changed this tradition, posing a danger to the lives of future emperors. And the first emperor to suffer this fate was Liu Yu's great-grandson.
In 477, Liu Yu's Southern Song Dynasty came to an end, with Liu Yu's emperor Liu Yu being killed by the victorious general Xiao Daocheng, and Liu Yu's younger brother Liu Huai, both of whom were Liu Yu's great-grandsons, succeeded to the throne as emperor. Two years later, under the pressure of Xiao Daocheng, Liu Huaichan gave up the throne, the Southern Dynasty and the Song Dynasty were overthrown, and the Southern Dynasty Qi came into being. Liu Huai did not accept fate as calmly as Sima Dewen, and kept sighing: "I wish to live in the world, and never give birth to an imperial family again." Liu Huai was eventually imprisoned by the defenders in the Dantu Palace, and during a riot, Liu Huai was killed by the defenders. What Liu Yu did back then is now the unfortunate fate of his children and grandchildren, and this can also be seen as a fair response.