1644 ( Ming Dynasty Chongzhen seventeenth year, Dashun Yongchang first year) on March 19, the leader of the peasant uprising army and the founder of the Dashun regime Li Zicheng led his army to invade Beijing. Emperor Chongzhen of the Ming Dynasty hanged himself in Meishan (today's Jingshan), and the Ming Dynasty officially withdrew from the stage of history. According to the conventional trend, Dashun should replace Ming Dynasty at this time, completing the replacement of the old and new dynasties. However, this time, history has reached a new turning point. In early April, news of the Dashun Army's capture of Beijing reached Liaodong 's Manchu . The Manchu and Qing Regent Dorgon immediately decided to take advantage of the Dashun Army's unstable foothold to quickly send troops south to compete in the Central Plains.
After Li Zicheng moved into the capital, he immediately sent people to Shanhaiguan to recruit Ping Xibo Wu Sangui who surrendered to the Ming Dynasty, Li Yutian, the governor of Liaodong, and Shanhaiguan General Soldier Gao Di. Wu Sangui and others believed that the general trend of the world had been decided, and Li Zicheng's offer of "promising the title of marquis for his father and son" was quite generous, so they decided to accept the surrender. Subsequently, Wu Sangui, on Li Zicheng's order, led his troops from Yongping Mansion to Beijing to meet the new master.
Around March 26, when Wu Sangui led his troops to Yutian County, Hebei Province, he suddenly changed his mind and rushed back to Shanhaiguan with his troops. With lightning speed, he raided Tang Tong, who was sent by Li Zicheng to Shanhaiguan to take over the defense. (formerly the commander-in-chief of Miyun in the Ming Dynasty, Li Zicheng surrendered after conquering Juyongguan ). Tang Tong's troops were far inferior to Wu Sangui's, and he was caught off guard. He was quickly defeated and retreated with the remaining troops to a stone not far from Shanhaiguan. Wu Sangui reoccupied Shanhaiguan.
Shanhaiguan is located between the two major forces of Qing and Shun. Wu Sangui's return to Shanhaiguan was obviously a break with the Dashun regime, so he had only the last option left in front of him: surrender to the Manchus.
The Manchu and Qing side originally planned to bypass Shanhaiguan and break through the border wall from Jizhou and Miyun areas to enter the pass. On April 15, when the Qing army arrived in Weng, they unexpectedly received a letter asking for help from Wu Sangui. Dorgon immediately decided to change the route and approach Shanhaiguan.
On the other side, when Li Zicheng learned about Wu Sangui's rebellion, he immediately sent envoys to comfort him. But at this time, Wu Sangui had already planned to go all the way, so appeasement was ineffective. In the end, Li Zicheng decided to send troops to quell the rebellion.
At that time, the number of troops Li Zicheng brought to Shanhaiguan was about 100,000. This army had followed Li Zicheng in the north and south for many years and was the absolute elite of the Dashun army. Wu Sangui's troops in Shanhaiguan were about 50,000, but considering the prevalence of the retainer system in the army in the late Ming Dynasty, only a few retainers were truly capable of fighting. Therefore, the Dashun Army still has a great advantage over the Wu Army. However, the Qing army led by Dorgon was about 80,000 people, and there is no doubt that the Qing army's combat effectiveness was significantly higher than that of the Dashun army and the Wu army.
On April 21, the Shanhaiguan War officially started. After a day and night of fierce fighting, Dashun's army gained the upper hand. Seeing that the situation was critical, Wu Sangui personally ran to Weiyuan Terrace, only two miles away from Guancheng, and asked for help from the Qing troops stationed here to watch the battle. Dorgon saw that Dashun's army and Wu's army were exhausted from fighting, so he ordered the Qing army to attack in full force. The Qing army itself had a strong fighting capacity, and with its ease of waiting for work, it had every advantage. Therefore, when the Qing army entered the battlefield, the Dashun army resisted tenaciously, but was eventually defeated.
The Battle of Shanhaiguan finally ended with the victory of the Qing and Wu coalition forces. So the question is, where did Li Zicheng lose? Judging from the direct results, the Dashun army fought with 100,000 against 130,000, and it was obvious that they lost because of insufficient strength. But the reason for the shortage of troops is not that simple.
At that time, the total military strength of the Dashun regime in various places was more than one million, but Li Zicheng only led more than 100,000 people to conquer Beijing. After occupying Shanxi, Jifu, and Shandong, the military strength was further dispersed. The remaining large numbers of main troops are distributed in the northwest, Huguang, Xiangyang and other four prefectures, Henan and other places. For example, Li Zicheng deployed 70,000 troops headed by general Bai Wang in the Jingxiang area of Huguang, and later sent Mianhou Yuan Zongdi to lead one of the five main rear camps to support. Until the Dashun army was defeated in Shanhaiguan, the armies of Yuan Zongdi and Bai Wang were still stranded in Henan and Huguang .In other words, Li Zicheng only saw that the overthrow of the Ming Dynasty was imminent, so he divided his troops across the country and was eager to pacify the world. But he failed to see that the Manchu Qing Dynasty entrenched outside the pass was the real opponent. In other words, if the army Li Zicheng brought to Shanhaiguan was not 100,000 but 200,000, then it would be uncertain who would win the battle at Shanhaiguan.
In addition to the limitations of his strategic vision, Li Zicheng also had major problems in recruiting and surrendering Wu Sangui. Wu Sangui did intend to surrender to the Dashun regime at the beginning. On March 22, he wrote in the notice of peace and security posted in Yongping Mansion, where the army was stationed: "This town led his troops to meet the new master, and he did not commit any crimes during the autumn. Your people need not be alarmed." Then he went to Beijing with his troops to prepare for Li Zicheng's appointment. But when Wu Sangui led his troops to Yutian County, Hebei Province, not far from Beijing, he suddenly regretted his decision.
There are several theories about the reasons for Wu Sangui’s sudden change of attitude. The most widely circulated theory is that his concubine in Beijing Chen Yuanyuan was forcibly taken away by Liu Zongmin, the “second in command” of the Dashun regime. ". Is this really the case? The answer is obviously no. At that time, Wu Sangui had more than 30 family members in Beijing, including his father Wu Xiang. Wu Sangui was an experienced political figure, and he was not a young man in his 10s or 20s. How could he risk his whole family for the sake of a concubine?
In fact, the main reason for Wu Sangui's temporary rebellion had a lot to do with the Dashun Army's pursuit of stolen goods and pay in the capital. Li Zicheng's Dashun Army always adhered to the policy of "no food when the king comes" in the process of conquering the country. But if King Chuang refuses to pay for food, what will his army eat? The answer is to eat the big ones. Every time Li Zicheng's army captured a state or county, they would confiscate all the property of the officials, gentry, landlords, and wealthy households in that state and county to use as military supplies. During the uprising stage, there was nothing wrong with this approach. After all, officials, gentry, and landlords were class enemies of Li Zicheng. But when Li Zicheng captured Beijing, he should have reestablished a new order, because all officials, gentry, landlords, and ordinary people would theoretically become his subjects. However, Li Zicheng's army still used the same method of chasing stolen goods to provide payment in Beijing, which made everyone in Beijing's officials and gentry feel in danger.
It was against this background that when Wu Sangui arrived in Yutian County, Hebei with his army, he received news from Beijing. Some said that his father Wu Xiang had been arrested by Li Zicheng's people to recover stolen money, and some said that Wu His home was ransacked by Li Zicheng's people. Although there are different opinions, it is self-evident that the shock this news brought to Wu Sangui, who was already uneasy. It was based on this information that Wu Sangui believed that going to Beijing would be a sheep in the tiger's mouth, so he abandoned the safety of his family, returned to Shanhaiguan with his army, and surrendered to the Manchus. In fact, it is true that Li Zicheng's people were pursuing stolen money and subsidies in Beijing, but they did not pursue the Wu family. However, these belated news were completely unimportant to Wu Sangui, who had already rebelled. In short, Li Zicheng did not do his ideological work well, which caused Wu Sangui to seriously misjudge.
If Wu Sangui had not rebelled at that time. When the Dashun Army fought against the Manchu Qing, at least they would not face the problems of pitting few against many, or pitting tired troops against elite troops. So even if there is a gap in combat effectiveness between the two sides, it will not lead to a complete defeat like later.
References: "History of the Ming Dynasty", "History of the Southern Ming Dynasty", "Ping Kou Zhi"
