The fundamental objective of the Ballistic Missile Defense (BMD) program is to develop the capability to defend forces and territories of the United States, its allies and friends against all classes and ranges of ballistic missile threats.

On December 17, 2002, President George W. Bush directed the Department of Defense to begin fielding in 2004 a capability to protect our homeland, deployed forces, and our friends and allies from ballistic missile attack.

The Missile Defense Agency (MDA) has developed a research, development and test program focusing on missile defense as a single layered defense system. The structure involves three basic phases of ballistic missile trajectories: boost, midcourse and terminal.

Boost phase is the portion of flight immediately after launch, when the missile is to gain acceleration under power to lift its payload into the air (airspace). This lasts 3-5 minutes. Midcourse phase is the longest part of the missile flight. It is where the missile payload has separated from the booster rocket and is coasting unpowered toward a target. This phase can be as long as 20 minutes. The final phase is called terminal. This is when the missile's warhead re-enters the earth's atmosphere and falls towards its target, propelled only by its momentum and the force of gravity. However, its speed can be thousands of miles per hour. This phase lasts approximately 30 seconds.