Yang Zhao
In winter 604, believing in the words of the sorcerer Zhangchou Taiyi () that the geography of Chang'an was not conducive to his health, Emperor Yang went to Luoyang, designating it as the eastern capital, and would rarely return to Chang'an thereafter. He ordered that major construction projects be carried out at Luoyang, commensurate with the necessities of having it as the actual capital, and he left his oldest son, Yang Zhao the Prince of Jin, in charge of Chang'an. He conscripted several hundred thousands of young men to dig a lengthy trench to surround the Luoyang region, intending that it serve as a defense perimeter. He also ordered that women and servants be exempted from head taxes, and that men would only be considered adults (i.e., subject to conscription) when they turn 21.