In the ninth year of Tang Gaozu Wude (626 AD), Li Shimin launched the famous "Xuanwumen Rebellion", in which he executed his brother Li Jiancheng, the crown prince, and his younger brother Li Yuanji the Prince of Qi, and then his father Li Yuan, Tang Gaozu, announced that he would be crown prince, and it did not take long for him to give him the throne. Li Shimin is the famous Ming Jun and Ren Jun Tang Taizong in Chinese history.
However, after Emperor Taizong of Tang ascended the throne, Li Yuan, who was revered as Emperor Taishang, did not have a good life--mainly because he was often counted down by this Ming Jun, and was picked up by various faults to demean himself and elevate Ming Jun.
Soon after Li Shimin ascended the throne, he began to publicly criticize various maladministrations during the Wude period. For example, he asked the minister above the court, "Is it beneficial to the world to seal the sect's sons?" Obviously, what Li Shimin said was that Li Yuan should not divide li tang sect room on a large scale, and he believed: "He is the son of heaven, so he raises the people, how can he work for the people to raise his own clan room?" When Li Shimin said this, there was of course a voice of agreement above the court, so Li Shimin demoted all the county kings that Li Yuan had once divided into county princes. You see, this makes Li Yuan more embarrassed.
For another example, Li Shimin issued an edict in September of the second year of Zhenguan (627 AD), which probably means: "It is really pitiful that the palace women are imprisoned in the deep palace, and the Sui Emperor collected countless women in the world at the end of the Sui Dynasty, so that the place where the emperor could not go several times in his lifetime was full of palace women, which was really a tyrannical thing." So I now issue an edict to let these poor people go home and obey them to marry. The historian Lü Simian commented after this edict that the maladministration of the Sui Dynasty's Guangcai palace women was not abolished until the Taizong period. ”
Li Shimin then purged the political forces around Li Yuan, one of the key figures involved in planning the Jinyang uprising, and was appointed by Li Yuan as prime minister after the founding of the Tang Dynasty. However, as soon as Li Shimin came to power, he first found a reason to exile him, and Pei Huan was not convinced, after all, he was the current prime minister, how could he be exiled without a word? Li Shimin was anxious and said to him: "Ji Gongxun yong, not to this point, in vain with grace, especially in the first place." At the time of Wu De, the political punishment was fierce, the official was in order, and the reason for the office was public. But with old feelings, we can't do the utmost law, and we can sweep the grave, so why should we resign? "The meaning is clear—what's so great about you Pei Ning?" Isn't it close to the Emperor Taishang? During the Wude years, the dynasty was abolished, and there were many evils, but you (and) family (high) gang (ancestor) tossed? Don't talk nonsense, get away from me (the Emperor Taishang)!
In addition, Li Yuan's freedom in life was also restricted--when the Xuanwumen coup d'état occurred, Li Yuan was originally playing in a boat, and the days were so moist at that time, but after Li Shimin came to power, he moved Li Yuan from the comfortable Taiji Palace to the Da'an Palace (that is, the Hongyi Palace), which was house arrest. Although later on the occasion of a good festival or a great event in the country (such as the pacification of the Turks), Li Yuan would convene a family banquet, and Li Shimin would openly play the pipa, but this happiness was always short-lived.
Li Shimin's treatment of Li Yuan made many people unable to look down, such as Wei Zheng, who dared to say that he once taunted Li Shimin in public--after Li Yuan's death, his dedication was only six zhang high, far lower than the specifications of the emperor's nine zhang. However, after the death of Li Shimin's eldest grandson Empress, Li Shimin built a tower in the city to look at Empress Changsun from afar. He not only took the stage to overlook the distance himself, but also took the minister with him, and once happened to take Wei Zheng with him. Li Shimin said, "Look at how spectacular that mausoleum is!" Wei Zheng pretended not to see, and Li Shimin was puzzled--such a tall tower, such a high mausoleum, you can't see it? Wei Zhengcai pretended to suddenly realize, "It turns out that the emperor said zhaoling, I thought it was a dedication to the tomb, no wonder I can't see it!" ”
Therefore, in general, after Li Yuan abdicated, although he had no worries about food and clothing, he nominally had a higher status than the emperor. But after all, Li Shimin obtained the throne through a coup d'état, so he had to guard against Li Yuan in many ways. For example, the expulsion of Pei Huan is probably because Li Shimin is worried that Li Yuan will carry out restoration under Pei Huan's planning.