Terminal High Altitude Area Defense (THAAD) is a transportable system that intercepts ballistic missiles inside or outside the atmosphere during their final, or terminal, phase of flight. THAAD uses a one-stage hit-to-kill interceptor to destroy incoming ballistic missile targets. THAAD is able to intercept incoming missiles both inside and just outside of the Earth’s atmosphere at a range of 200 kilometers, which mitigates the effects of weapons of mass destruction before they reach the ground. The ability to intercept both inside and outside the atmosphere makes THAAD an important part of layered missile defense concepts, as it falls between the exclusively exo-atmospheric Aegis interceptors and the exclusively endo-atmospheric Patriot interceptors.