What is history: it is the echo of the past to the future, the reflection of the future on the past. - Hugo
Xu Da's two releases of Emperor Yuanshun happened within a year or two after Zhu Yuanzhang had just established the state and became emperor, mainly in the course of Zhu Yuanzhang's northern expedition to the Yuan Dynasty.
The first time Emperor Yuan Shun was released was in the Yuan capital beiping. In July of the first year of Hongwu, Xu Da led the Powerful Ming army all the way to the present city of Tongzhou in Hebei Province, and stationed in the city, preparing to fight hard against the Yuan Dynasty, but that night Emperor Yuan Shun fled from the Yuan capital with his harem and ministers, and Xu Da thought that there would be a big battle and continued to prepare. Seven days later, he learned through scouting that Emperor Yuan Shun had run away, so he quickly sent troops to enter Yuan Dadu. After killing the remaining Queen of Jianguohuai, she captured the Yuan capital Beiping. Obviously, this is not Xu Da's intention to let go of Emperor Yuanshun, but Xu Da's strategic judgment is wrong, thinking that Emperor Yuanshun will have the heart of breaking the net after the next siege, after all, the Yuan Dynasty at that time only lost part of the southern territory, and the Yuan Dynasty's army was still there.
The second time was in kaiping, the capital of yuan (present-day Zhenglanqi, Inner Mongolia, on the north bank of the Lightning River). It is said that after Emperor Yuanshun escaped from Yuanshangdu last time, Xu Da led a large army to pursue him, and after arriving in Shangdu, Xu Da surrounded Yuanshangdu again, but this time Emperor Yuanshun escaped from the weak point in the encirclement and successfully escaped Xu Da's capture. I don't know if this was Xu Da's negligence, or a trap of preparing to wait for the rabbit, or even Xu Da deliberately let emperor Yuan Shun go. Because according to Feng Menglong's "Wisdom Tank Shangzhibu", Xu Da once said, "Although yidi, it tastes the world of the emperor for a long time." What about our Lord? Will the ground be split and sealed? Or is it willing? If neither is possible, it is easy to fix it. It can be seen that Xu Da most likely had the intention to let Emperor Yuan Shun go.
As for why, it is very likely that he was instructed by Zhu Yuanzhang. Zhu Yuanzhang This is a person who respects heaven and attaches great importance to the way of kings and subjects. It can be seen from his abolition of the chancellor and the change of the holy will as "Emperor Fengtian Carrier".
Zhu Yuanzhang did not want his courtiers to kill Emperor Yuanshun from his heart, after all, Emperor Yuanshun was an emperor, even if it was a foreign minister who killed the king, it was also a great rebellion, and Zhu Yuanzhang would not allow it. However, zhu Yuanzhang himself wanted to be emperor, he had to start from emperor Yuan Shun, such a person, killing is not killing or not killing, had to be let go. In this way, the way of the monarch was completed, the Yuan Shun Emperor did not die at the hands of the courtiers, and the active concession of the Yuan Shun Emperor could also make the next Daming more justified. Wouldn't it be better to kill two birds with one stone?