Jianwen Emperor
In response to the Jianwen Emperor's crackdown on the influence of imperial princes, Zhu Di (the Prince of Yan and fourth son of the Hongwu Emperor) captured and coöpted the princedom of his 17th brother, Zhu Quan (the Prince of Ning), thereby putting himself in control of the bulk of the Ming army in northern China. He also won the support of several Mongol tribes when he burnt down Daning, the capital of Zhu Quan's princedom, and evacuated Ming forces from the princedom. Later, Zhu Di feigned illness and madness to convince the Jianwen Emperor to release three of his sons, who were being kept as hostages in Nanjing to prevent Zhu Di from rebelling against the emperor. However, the Jianwen Emperor became wary of Zhu Di and tried to arrest him later but failed. Zhu Di then launched the Jingnan Campaign against the Jianwen Emperor.