It was a very important role, and if Khalkha had not been cleared, the threat to the northern part of the Qing Dynasty would have been even more severe. The situation in the northwest of the Qing Dynasty in the 17th century was very grim, the main problem was that the Mongol migration could also be said to be the various conflicts caused by expansion, at the end of the 16th century, with the spread of Tibetan Buddhism to Mongolia, Tibet used Mongolia to spread Buddhism on the steppe, I don't know if it is a blessing or a curse for Tibet? This is also the main reason why the Mongol forces were able to interfere in Tibetan politics and religion. The Buddhistization of Mongolia triggered changes in the political order and social structure of northern China. The first half of the 17th century was a turning point in the Qing Dynasty's move towards Mongolia and Tibet, which I personally think are: the conversion of the Chahar Mongols. Second: the conversion of Khalkha. The former's submission to the Qing Dynasty expanded the Qing Dynasty's influence on Mongolia. The latter's submission to the Qing Dynasty deepened its control over Mongolia, which was not complete control of Mongolia.
First of all, this Khalkha was once tense with the Qing Dynasty in the mid-17th century, do not think that the enemy of the Qing Dynasty seems to be only Dzungar, in fact, in that period the Dzungar was not as strong as the Threat to the Qing Dynasty. Khalkha has always wanted to control the southern Mongolian desert, and the Mongolian southern region after the death of Lin Dan Khan, it submitted to the emperor Taiji, and it is precisely because the dragons are leaderless and the Qing Dynasty has a weak control over the southern Mongolia, so the Khalkha has an opportunity. Such as the Tengjisi rebellion, the Burney rebellion, the plundering of Bahrain, Tumut, including the southern Mongolia and other events are directly caused by Khalkha, Khalkha returned to the Qing, so that the Qing Dynasty got a full reason to participate in the entire Mongolian affairs, in the end what reason can make Khalkha willing to return to the Qing, I think it is Dzungar, in fact, Khalkha and Dzungar both want to be the Great Khan of Mongolia, the rise of Dzungar is disastrous khalkha If you want to survive, you must choose... Why did LinDan Khan, Tushetu Khan and Geldan all fail?
To put it bluntly, if Khalkha wants to conquer Mongolia, it must defeat Dzungar and the Qing Dynasty, and the environment faced by Dzungar is more dangerous, one occupies the Qing Dynasty in the central plains, the other is Russia, the comprehensive national strength of these two countries is much stronger than Dzungar, and both are in their heyday, the rise of Russia and the Qing Dynasty directly compressed the living space of Dzungar, and the failure of Dzungar was inevitable.