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 a