What happened to the Vietnam War during the Qianlong period of the Qing Dynasty?

The Qing-Vietnam War, that is, the Battle of Annan, was one of the foreign wars launched during the Qianlong period. During the Qianlong period of the Qing Dynasty, Emperor Qianlong once launched a war against Vietnam. The banner of the Qing army is to support the revival of the Li Dynasty. However, due to the deep isolation and arrogance of the soldiers, the Qing army who went south to Vietnam won first and then lost. ?

After the war, the Lee Dynasty, which supported Vietnam in the Qing Dynasty, failed to restore the country, while the Xishan Dynasty completely ruled Vietnam. Since then, although the Xishan Dynasty of Vietnam also wanted to attack Guangxi, it was unable to go north because of insufficient troops and inadequate preparation, and the death of Emperor Nguyen Van Yuet.

During the Qianlong period, wars broke out between the Qing Dynasty and Myanmar and Vietnam. However, the Qing-Myanmar war was provoked by Myanmar and was finally pushed back to Myanmar by the Qing army. However, the Qing army itself suffered heavy losses and lost a number of government officials. Although Emperor Qianlong regarded the Burma War as one of the peerless martial arts, it was actually a fiasco.

The Qing-Vietnam War was provoked by the Qing Dynasty, but the loss was not as great as that of the Qing-Myanmar War. The strength of the Xishan Dynasty in Vietnam was not comparable to that of the Pound Dynasty in Myanmar, so it did not take the initiative to attack the Qing Dynasty. At that time, nearly 20 years had passed since the Qing Dynasty eliminated the Junggar khanate. During the Qing Dynasty, the country was closed to the outside world for a long time, and officials were corrupt. However, in the face of small Southeast Asian countries like Myanmar and Vietnam, it still had a volume advantage.

In A.D. 1778, Ruan Wenyue, the leader of the Vietnamese Rebel Army, and others were dissatisfied with the dark rule of the Li Dynasty, claiming to be emperors and establishing the Xishan Dynasty. In the struggle between the Li Dynasty and the Xishan Dynasty, the Li Dynasty, which had been established for more than 300 years, failed and retreated to Guangxi. The Li Dynasty sent people to the Qing Dynasty for help, which was responded by Emperor Qianlong.

Emperor Qianlong believed that the Qing soldiers were better than Ma Zhuang and had the obligation to maintain the order of the surrounding vassal States. At the same time, Qianlong felt that the Li Dynasty ruled Vietnam for more than 300 years and remained loyal to the Qing Dynasty. So at the end of 1788, he sent Sun Shiyi, the governor of Guangdong and Guangxi, to lead a 20,000-strong army to attack Vietnam under the banner of supporting the restoration of the Li Dynasty. Although the Qing army sent tens of thousands of troops, in fact, apart from porters and grooms, there were only more than 10 thousand real soldiers.