United States national missile defense
National missile defense (NMD) is a generic term for a type of missile defense intended to shield an entire country against incoming missiles, such as intercontinental ballistic missile (ICBMs) or other ballistic missiles.This is also used to refer to the American nationwide antimissile program the United States has had in development since the 1990s. After the renaming in 2002, the term now refers to the entire program, not just the ground-based interceptors and associated facilities. This article focuses mainly on this system and a brief history of earlier systems which led to it.Other elements yet to be integrated into NMD may include anti-ballistic missiles, or sea-based, space-based, laser, and high altitude missile systems. The NMD program is limited in scope and designed to counter a relatively small ICBM attack from a less sophisticated adversary. Unlike the earlier Strategic Defense Initiative program, it is not designed to be a robust shield against a large attack from a technically sophisticated adversary.