In 1644, the Dashun army led by Li Zicheng conquered Beijing, and the Chongzhen Emperor Zhu Youzhen hanged himself in the coal mountain.

After Li Zicheng's rebel army occupied Beijing, he quickly degenerated, his generals were arrogant, and at the same time, because of the competition for Chen Yuanyuan, he angered Wu Sangui and forced him to the Manchu Qing.

Dolgon led the Eight Banners Army and Wu Sangui, the general soldier of the Ming Dynasty, to join forces and fight Li Zicheng inside and outside the Shanhai Pass.

Li Zicheng was defeated, withdrew from Beijing, and continued to fight in Henan and Shaanxi.

After the Qing army captured Beijing, it concentrated its forces and continued to attack the Dashun army in Guanzhong. The Dashun army was forced to withdraw from Guanzhong in two ways and enter Huguang through Xiangyang.

In the south, Zhu Yousong, the king of Fu, with the support of Gao Jie, Huang Degong, Liu Liangzuo, Liu Zeqing, and Ma Shiying, the governor of Fengyang, supervised the country in Nanjing, and became emperor on May 15, and the following year was changed to the first year of Hongguang.

At this time, the Dashun Army occupied a part of Hubei, Zhang Xianzhong's Great Western Army occupied the Sichuan area, and the Manchu Qing Dynasty occupied most of the northeast, northwest, and north China. The remnants of the Ming Dynasty possessed half of China south of the Huai River.

In March 1645, the Manchu Qing began their southern expedition.

At this time, there was a fierce party struggle within the Hongguang regime, and the prince case broke out, and Zuo Liangyu in Hubei did not dare to fight head-on with Li Zicheng's Dashun army, and in the name of "Qing Jun's side", he went east along the Yangtze River to fight for the Nanming regime.

Ma Shiying, the first assistant of the cabinet of the Hongguang Dynasty, was forced to urgently transfer the four towns of Jiangbei to meet the left army, causing the Jianghuai defense line facing the Qing army to fall into emptiness.

In April 1645, Zuo Liangyu died of illness in the Jiujiang boat during the march.

Zuo Liangyu's subordinates kept it secret and jointly elected his son Zuo Mengeng as the military master.

Zuo Mengeng led the rest of the surrender to the Qing Dynasty, and the Manchu Qing Dynasty occupied Hubei and other places, and also had a large number of ships, and the Yangtze River no longer existed.

The Qing army easily broke through Xuzhou and Yangzhou.

When the Yangzhou pool was broken, the Qing army slaughtered the city, and 800,000 people died in Yangzhou, which was known as "Yangzhou Ten Days" in history.

Subsequently, the Qing army crossed the Yangtze River and conquered Zhenjiang, and Emperor Hongguang hurriedly fled to Wuhu.

On May 15, the ministers of the Hongguang regime offered Nanjing to surrender to the Qing Dynasty;

On May 22, Emperor Hongguang was captured and sent to Beijing, where he was executed by the Qing army the following year.

After the fall of Nanjing, in 1645, in the leap month of Ding Wei, the Tang King Zhu Yujian was supported by Zheng Zhilong and others, and proclaimed himself emperor in Fuzhou, Fujian, and changed the Yuan to Longwu.

About 40 days after Zhu Yujian became emperor, Zhu Yihai, the king of Lu, supervised the country in Shaoxing, Zhejiang.

The situation of one country and two lords made the Longwu regime and the Lu Wang regime fight for the orthodox status like fire and water, and each fights for itself.

When the Qing army moved south again, neither the Longwu regime nor the Lu regime had established a solid defensive line.

In May 1646, the Manchu Qing Dynasty's southern general Belebolo broke through the Qiantang River, and the cities of Shaoxing, Hangzhou, Yiwu, and Jinhua were lost one after another.

Zhu Yihai, the king of Lu, went into exile at sea, went to Shipu, and then went to Zhoushan.

In August, seeing that the Manchus were approaching step by step, and at the same time hearing the promise to make himself the governor of Fujian and Guangdong, Zheng Zhilong was determined to defect to the Manchus, Zheng Zhilong ordered all the Xianxia Pass defenders guarding the northern gate of Fujian to withdraw to Anping, and also recalled his eldest son Zheng Chenggong, who was leading the troops outside.

When Zhu Yujian, Emperor Longwu heard this, he fled to Tingzhou and was taken captive, and died on hunger strike.

On November 15, 1646, Zheng Zhilong ignored Zheng Chenggong's bitter advice and went north to Fuzhou to surrender to the Qing Dynasty. The Manchus repented and took Zheng Zhilong hostage to Shangjing, while sending troops to attack his old nest, Anping Town.