In 1644, Li Zicheng captured Beijing, Chongzhen Emperor was hanged, and Ming dynasty perished. After that, situation in China began to undergo rapid changes. First, Qing Dynasty in northeast invaded Shanhaiguan and drove Li Zicheng out of Beijing. The Qing dynasty then announced that Beijing would become its capital and unify China. Secondly, remnants of Ming dynasty retreated to southeastern half of country, forming large separatist regimes and fighting each other. After Qing dynasty entered customs, they quickly destroyed peasant armies such as Li Zicheng and Zhang Xianzhong and began to attack Nanming.

In June 1645, with support of Zheng group, Zhu Yujian, king of Ming and Tang dynasties, proclaimed himself emperor in Fuzhou and established Long regime. In July, Longwu regime began sending troops to attack Jiangxi, Zhejiang, and other places to counter Qing dynasty. Since Qing army issued an "order to shave off hair" at that time, which led to ethnic conflicts and fierce resistance in south of Yangtze River, it was difficult for Qing army to go south for a while, and Nanming force recovered slightly. In November, Longwu regime regained large tracts of land in Hubei, Hunan and Jiangxi. When two armies reached a stalemate, Longu regime wrote a letter of credence to Japan, content of which was as follows:

This letter is recorded in The Japanese Beggars by Huang Zongxi. At that time, Zhou Hezhi, governor of Nanming fleet, was ordered to bring a group of ambassadors to Japan, he met with Japanese shogunate and asked for support from Ming dynasty. The Japanese shogunate agreed to send 30,000 troops to support it, and did not need material assistance from Ming dynasty. But when Zhou Hezhi returned home, ministers opposed Japan's aid. Because ministers were worried that Japan would be unkind and take opportunity to occupy Ming lands. So plan was cancelled.

Coincidentally, in 1646 Emperor Nanming Yongli attempted to seek Portuguese help in Macau, so Portugal sent 300 cannons to help Nanming regain lost ground. After that, Yongli Emperor joined Roman Catholic Church with all members of Nanming royal family, and all were baptized by Empress Dowager Wang, Empress Wang, prince and concubines in harem. In October 1648, Yongli Emperor again turned to Macau for help, but Portugal at that time gave only a hundred muskets.

That's why Queen Mother wrote a letter of distress to Pope and not to Yongle Emperor. The letter was delivered by Polish Jesuit Mig and Chen Ander and eventually reached Venice to meet with Doge. The governor studied for three years, but never sent troops, but preferred to pray to Ming dynasty. The content of this letter is as follows:

As Sole Heir of Empire, Representative of God in East, Protector of Eastern Christians, Prince Emperor of Central Plains, Protector of North Korea, Uzbeks and Sali Uighurs, and Guardian of East Asian Kingdom, Ling Dan Han's friend of Chahar tribe, Tian Han Mongolian pastures and prince of Town of Eastern Fantasy in hearts of European countries. Here I would like to convey greetings to His Excellency Pope Innocent X. I have sad news to inform you that in our great country, where Catholicism is state religion, Ming Empire, during southern invasion of Tatars, peasant riots, military-aristocratic rebellions and Under combined blow of Dutch attack, present empire is already falling apart, and unbelieving in God barbarian Tatars are slaughtering Lamb of Lord in various parts of empire. These eastern heretics are still spreading their heretical beliefs in an endless stream, trying to give flock of Lord into arms of devil, so they ask Pope Innosencer X to organize a crusade and start a holy war so that glory of God will shine in east again, and may God bless the Ming dynasty peace and prosperity. Sincerely, Crown Prince Konstantin, Dowager Empress Maria and Queen Helena.

The above two letters show how helpless remnants of Ming Dynasty are. In order not to be destroyed by Qing Dynasty, he would have preferred to fundamentally change his faith. And European powers thousands of miles away are currently engaged in Thirty Years' War and have no time to look back. Even if European powers came to east without participating in war, they would not be able to save Ming dynasty.