When the Jingnan Campaign ended, no one knew what had become of the Jianwen Emperor.
Tips
mistakes
Read 难 as nàn 'calamity' here, not nán 'difficult': 靖难 means 'to quell the troubles'. 朱棣, Prince of Yan, claimed to be saving his nephew's throne from bad ministers, the old pretext of 清君侧.
history
The Jianwen Emperor vanished when the palace in Nanjing burned in 1402. Legend says he escaped dressed as a monk, and the official Ming history says 郑和's voyages were partly meant to track him down overseas.