In a speech at National Defense University on May 1st 2001, President George W. Bush restated his administration's goal of developing a system to protect the US, and perhaps its allies, against ballistic missiles. He alluded to a wide range of possible approaches to this task, though no specific systems have yet been chosen. This site is a guide to potential technologies that might be used in a national defense against ICBMs. Note that while ICBMs are the only land-based ballistic missile threats to US territory, American allies might be threatened by shorter range theater missiles and thus require theater missile defenses for protection.
Missile defenses may be broadly grouped according to the point in the missile's flight that is targeted:
Each phase presents its own distinct challenges to the defense, as discussed in the following links: