From Prince to Emperor
In 1641 Luoyang fell to the rebel army of Li Zicheng. Zhu Yousong escaped, but his father was killed, and in 1643 he succeeded to his father's title as Prince of Fu.
When the rebels advanced again in 1644, he fled to Weihui, the seat of his kinsman Zhu Changfang, Prince of Lu, and from there to Huai'an, in the company of other refugee princes.
The Succession Crisis
In April 1644 Li Zicheng took Beijing and the Chongzhen Emperor took his own life. When the news reached Nanjing, the Ming's southern capital, its senior officials met to decide how to respond. The fate of Chongzhen's sons was unknown, and some argued it was too soon to name a new emperor, but most agreed that the loyalist cause needed an imperial figure to rally around.
By descent, the Prince of Fu had the strongest claim. The Taichang Emperor's surviving sons, the Tianqi and Chongzhen emperors, had left no heirs who could be found, so the choice passed to the sons of the Wanli Emperor. Zhu Changxun had been the eldest surviving brother of Taichang, and Zhu Yousong was his eldest son.
Some officials preferred the Prince of Lu, whom they thought more capable. The matter was settled by the military governor Ma Shiying, who backed the Prince of Fu and brought troops to Nanjing. Zhu Yousong was enthroned there in June 1644, and it was decided that the Hongguang era would begin with the following lunar year.