also called Star Wars
Proposed U.S. strategic defense system against nuclear attacks.
Announced as a 20-year, $20 billion effort by Pres. Ronald Reagan in 1983, SDI was intended to defend the U.S. from a full-fledged Soviet attack by intercepting ICBM s in flight. The interception was to be effected by technology not yet developed, including space-and ground-based laser stations and air-and ground-based missiles. The space component of SDI led to its being derisively dubbed "Star Wars" after the popular film. Though the program was roundly criticized by opposition politicians and arms-control advocates as unworkable and as a dangerous violation of the Antiballistic Missile (ABM) Treaty of 1972, Congress granted initial funding for it. Early development efforts were largely unsuccessful, and with the fall of the Soviet Union in 1991 the concept lost urgency. During the Bush and Clinton administrations, ballistic missile defense was scaled back to focus on protecting the U.S. from limited attack by a "rogue" state or a single accidentally launched missile. In 2002 the U.S. withdrew from the ABM treaty to begin active testing of a limited antimissile program. See also antiballistic missile .