High Quality Content by WIKIPEDIA articles! Ground-Based Midcourse Defense (GMD) is the United States system for intercepting incoming warheads in space. It is a major component of the U.S. missile defense strategy to counter ballistic missiles, including intercontinental ballistic missiles (ICBMs). GMD is administered by the US Missile Defense Agency (MDA), while the operational control and execution is provided by the US Army, and support functions are provided by the US Air Force. Previously known as National Missile Defense (NMD), the name was changed in 2002 to differentiate it from other U.S. missile defense programs, such as space-based and sea-based intercept programs, or defense targeting the boost phase and the reentry phase (see flight phases).