With his sons free, Zhu Di began to fight the Jianwen Emperor. At first, he said that he really wanted to protect his nephew from the "bad helpers" who were telling the emperor to fight his own family. After he took the capital, though, he rewrote all the government papers to pretend the Jianwen Emperor had never been the emperor. The four years of his nephew's control were dated to the end of the Hongwu Emperor's era. Zhu Di began his new era at the next Chinese New Year and became the Yongle Emperor.