In the thirty-first year of Hongwu's reign, Ming Taizu Zhu Yuanzhang passed away, and the emperor's grandson Zhu Yunwen inherited the throne. After the new emperor came to the throne, in order to consolidate the imperial power, he quickly implemented the strategy of reducing vassal vassals, and vassal kings such as King Zhou and King Dai were deposed one after another. King Zhu Di of Yan raised his troops to resist in the name of "Jingnan Qingjun". It took four years for the Yan army to conquer Nanjing. On the day the city was destroyed, a fire broke out in the palace. The whereabouts of Emperor Jianwen Zhu Yunwen were unknown, leaving only a few unrecognizable and charred corpses.
After Zhu Di ascended the throne, he was always worried about the hidden danger that Zhu Yunwen might still be alive and waiting for an opportunity to return to the country. In the fifth year of Yongle's reign, he secretly ordered Hu Kedu to secretly investigate the traces of Emperor Jianwen in the name of looking for the immortal Zhang Sulu. After receiving the order, Hu Hui traveled all over the north and south of the Yangtze River. After more than ten years of arduous journey, he did not miss any clues.
In the 21st year of Yongle, Zhu Di was leading his army to march north and stationed in Xuanfu. Late at night, Hu Hui, who was tired of traveling, rushed from Beijing and asked to see the emperor. Zhu Di immediately dismissed his attendants and started a long secret conversation with Hu Hui, which did not end until the fourth watch. "History of the Ming Dynasty" contains a few words: "The most serious doubts can only be clarified." It is said that after this conversation, the doubts that had been lingering in Zhu Di's heart for many years finally disappeared. Although the content of this secret late-night conversation has not been recorded in official history, it undoubtedly solved the mystery of the whereabouts of Emperor Jianwen and became a key event affecting the political structure of the Yongle Dynasty.
