Eight Banners
There were not enough ethnic Manchus to conquer China, so they relied on defeating and absorbing Mongols, and more importantly, adding Han Chinese to the Eight Banners. The Manchus had to create an entire "Jiu Han jun" (Old Han Army) due to the massive number of Han Chinese soldiers who were absorbed into the Eight Banners by both capture and defection, Ming artillery was responsible for many victories against the Manchus, so the Manchus established an artillery corps made out of Han Chinese soldiers in 1641 and the swelling of Han Chinese numbers in the Eight Banners led in 1642 of all Eight Han Banners being created. It was defected Ming Han Chinese armies which conquered southern China for the Qing.