Li Zicheng, who survived, got the "post-happiness" of being an emperor, but this post-happiness was short-lived. Li Zicheng, who thought he could seize the world by laying down Beijing, immediately "herded sheep" after entering Beijing. His army plundered the wealth of the people everywhere, the discipline of the peasant army became increasingly corrupt, and the generals soon became corrupt.
At this time, the Nanming regime was particularly powerful, and the northern Manchu dynasty was eyeing up. However, Li Zicheng naively thought that if Beijing was laid, the world would be peaceful. As a founding emperor, he only destroys and plunders from beginning to end. A hero who can create a dynasty should first be a builder. In this respect, Li Zicheng and Zhang are not qualified.
Unqualified Li Zicheng will certainly not take Wu Sangui, who has been guarding Shanhaiguan, seriously. Finally, Wu Sangui colluded with the Qing soldiers to enter the customs, hit Li Zicheng hard, and then pursued them all the way. Emperor Li Zicheng only did it for 42 days.
Extended data:
Failure:
In October of the first year of Shunzhi (the first year of Dashun Yongshun, 1644), the Qing army captured Taiyuan, and then divided its troops south to the southeast of Shanxi. Liu Zhong, commander of Changzhi of Dashun Army, could not resist the enemy and was forced to lead his troops to Henan. At this point, only the southwest corner of Shanxi was controlled by Dashun Army, and Li Zicheng's Shanxi defense line basically collapsed.
/kloc-in late October, the Qing army attacked Shaanxi in two ways. A route led by King Azig of England, Wu Sangui and Shangkexi marched from Datong to Yulin, and then from northern Shaanxi south to xi 'an. Prince Yu Duo Duo, Kong Youde and Geng Yin attacked Tongguan all the way from Huaiqing, Henan. When Li Zicheng heard the news, he was not busy leading the troops to reinforce Tongguan. In December, the Qing army attacked Tongguan, and Dashun army took the lead. Liu Zongmin fought first.
References:
Li Zicheng-Baidu encyclopedia