How did the Qing army enter the customs at that time?

It was Wu Sangui who let the Qing army enter the customs.

As for the purpose: After Li Zicheng entered the city, Ming Chongzhen hanged himself, and Daming basically perished (Nanming ... is too short to count). Originally, Li Zicheng sent someone to surrender to Wu Sangui, and Wu Sangui was ready to surrender to Li Zicheng at this time (nonsense, the emperor didn't surrender, what are you waiting for? )。 But at this time, the news came that Li Zicheng Zhang Zhongxian couldn't control the discipline of his rebel army, which led to soldiers looting, the family was occupied by the rebel army and the whole family was finished. Of course, some people say that Chen Yuanyuan was occupied by rebel generals. Well, if you are Lao Wu, you will hate it. Turn around and return to Shanhaiguan immediately.

At this time, the Qing army sent Yuan Chonghuan's subordinate Zu Dashou (who had surrendered to the Qing army at this time) to surrender to Wu Sangui. Zu Dashou is Wu Sangui's uncle, and he paid a high price, so ... Please lower the switch.