Eight Banners
There were too few ethnic Manchus to conquer China proper, so they gained strength by defeating and absorbing Mongols. More importantly, they added 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 to all Eight Han Banners being created. Armies of defected Ming Han Chinese conquered southern China for the Qing.