Fighting rats.
Which is exactly how these people act. They live in caves, tunnels, and isolated mountain villages which are completely under their control. We need to use rat poison on them to decimate their ranks. Capture some of them, then infect them with a slow acting but very contagious and deadly virus or bacteria, Let them escape and run back to their nesting sites. The infection will spread rapidly and before they realize what's happening, most of them will be infected and dying.