Missile defense can take place either inside (endoatmospheric) or outside (exoatmospheric) the Earth's atmosphere. The trajectory of most ballistic missiles takes them inside and outside the Earth's atmosphere, and they can be intercepted in either place. There are advantages and disadvantages to either intercept technique. Some missiles such as THAAD can intercept both inside and outside the Earth's atmosphere, giving two intercept opportunities. 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. 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.