He then demoted Li Shiji to the post of the commandant of Die Prefecture (, roughly modern Gannan Tibetan Autonomous Prefecture, Gansu). Li Shiji, after receiving the order, departed without hesitation. (The modern historian Bo Yang, commenting on this incident, opined that this showed that, down inside, neither Li Shiji nor Emperor Taizong actually trusted each other, as Li Shiji was too capable for Emperor Taizong's liking. Another explanation is that the Taizong was playing an age-old trick to test Li Shiji's loyalty. While he's alive, he was able to handle Li Shiji; he was afraid that his son would not be able to do so after his death. He intentionally demoted Li Shiji to test his response. If Li Shiji showed any hesitation or unhappiness, he would have been executed and the new emperor would not have to deal with him. If Li Shiji didn't show any emotion about the demotion, the new emperor can promote him to show he liked him so Li Shiji would be loyal to him. This turned out to be a bad move. Years later when Gaozong tried to make Wu Zetian () his empress against the opposition of most high officials, Li Shiji decisively put the issue in Wu Zetian's favor by saying that's an internal issue of Gaozong.) Nine days later, Emperor Taizong died and was succeeded by Li Zhi (as Emperor Gaozong).