There are three main measures, the first is marriage, the second is flag-building, and the third is conquest.
In the early Qing Dynasty, Mongolia was divided into three parts: Monan Mongolia, Mobei Mongolia and Moxi Mongolia, and there were many small tribes in each part. These Mongolian tribes often fight with each other, and it is normal for small tribes to form alliances with powerful tribes in order to survive.
Nurhachi unified the ministries of Jurchen, established the post-Jin Dynasty, seized a large area of land in the Ming Dynasty, and after becoming powerful, he took the initiative to throw an olive branch to Mongolian tribes. In the late Jin Dynasty, a group of Mongolian tribes took refuge, among which the most staunch alliance was Horqin tribe. After becoming an alliance, Hou Jin strengthened his relationship with these Mongolian tribes through marriage.
In order to strengthen the control of Mongolian tribes and enhance the military strength of the late Jin Dynasty, Huang Taiji built a flag in Mongolian tribes after killing Chahar. After the flag was built, the Mongolian tribe really became a part of the Manchu dynasty, just like the inland administrative region. The Eight Banners of Mongolia were mainly built in Monan Mongolia, while Mobei and Moxi Mongolia were vassal departments, with a high degree of autonomy.
There were three major battles to recover Mongolia in Qing Dynasty. The first game was Huang Taiji's conquest of Lidan Khan, the second game was Kangxi's personal expedition to Grdan, and the third game was Qianlong's destruction of Junggar.
Li Dan Khan is a descendant of Genghis Khan and the head of Chahar Department. Huang taiji isolated Chahar through disintegration. 1632, Huang taiji led an army to join forces with the Mongolian tribal army and attacked Li Dan Khan. The defeated Li Dan Khan fled to Qinghai and died soon. After the death of Li Dan Khan, his daughter-in-law and son returned to Hetao area. 1635, Huang taiji sent dourgen to levy the Chahar department, and Li Dan Khan's daughter-in-law and son surrendered.
Chahar, Gurkha and Junggar are three powerful tribes in Mongolia. After Chahar was destroyed, the next goal of the Qing Dynasty was Gurkha. Gurkha was afraid and surrendered to the Qing Dynasty the next year.
Gerdan is the leader of Junggar khanate. He wanted to unify the Mongolian ministries and achieve the glory of Genghis Khan, so he colluded with Russia and repeatedly committed the Qing Dynasty, which became the biggest hidden danger of the Qing Dynasty.
Kangxi made appropriate concessions through the Sino-Russian Nebuchadnezzar Chu Treaty and put an end to Gedan's support behind Russia. Then concentrate on three personal expeditions to Gerdan, break Gerdan's camel array in Wulanbu, and defeat Gerdan's main force in Zhaomodo. Gedan fled, deserted and finally committed suicide.
After Gerdan's death, Junggar stopped for several years. By the Yongzheng Dynasty, the descendants of Gerdan began to make trouble again. Yongzheng conquered Junggar twice. The first one was Nian Gengyao, who won, and the second one was Fu 'erdan, who lost. Yongzheng's military ability is poor, and he dare not levy again.
During the Qianlong period, there was civil strife in Junggar, and Qianlong saw a rare opportunity to destroy Junggar. In the case of general opposition from ministers, Gan Gang went his own way and sent troops to attack Junggar. One * * * sent troops three times, but the first two times were ineffective and suffered heavy losses. The third invasion went smoothly and completely wiped out Junggar.