Strategic Defense Initiative (SDI), U.S. government program responsible for research and development of a space-based system to defend the nation from attack by strategic ballistic missiles (see guided missile). The program is now administered by the Missile Defense Agency (originally the Strategic Defense Initiative Office), a separate agency in the U.S. Dept. of Defense. SDI, popularly referred to as "Star Wars," was announced by President Ronald Reagan in a speech in Mar., 1983, and was derided by his critics as unrealistic. Space programs from other agencies and services were brought together in the organization. It has investigated many new technologies, including ground-based lasers, space-based lasers, and automated space vehicles. Critics argued that the original SDI program would encourage the militarization of space and destabilize the nuclear balance of power, and was technologically infeasible, based on untested technologies, and unable to defend against cruise missiles, airplanes, or several other possible delivery systems. In addition, some countermeasures to SDI technologies, such as decoy missiles and shielding of armed missiles, would be simple to implement. In 1987 the Soviet Union revealed it had a similar program.

The end of the cold war led to criticism that SDI was unnecessary, and in 1991 President G. H. W. Bush called for a more limited version using rocket-launched interceptors based on the ground at a single site. In 1993, SDI was reorganized as the Ballistic Missile Defense Organization (BMDO). The more limited system, called the National Missile Defense (NMD), is intended to protect all 50 states from a rogue missile attack, but the deployment of such a system was forbidden under the 1972 Anti-Ballistic Missile (ABM) Treaty. Russia opposed the NMD plan but, under President Putin, also proposed a mobile, pan-European missile defense system with a similar purpose that would not violate the ABM treaty. In 2001, President George W. Bush called for accelerated development of the NMD system, and subsequently withdrew from the ABM treaty to permit the system's development and deployment. Apparently successful early tests of the U.S. system were later revealed to have occurred after the odds of success had been enhanced (1984, 1991). Subsequent tests were generally more successful, although flawed or limited in certain respects, but tests in 2002, 2004, and 2005 involved failures. In 2002, President Bush ordered the deployment of a modest missile defense system by 2004, with interceptors based at sea and at Fort Greely, Alaska, and Vandenberg Air Force Base, Calif., and several interceptor missiles were emplaced by the end of 2004. Also in 2002, the BMDO was renamed the Missile Defense Agency (MDA). In addition to NMD, the MDA is also working to develop missile defenses for the battlefield as part of the Theater Missile Defense program.

Strategic Arms Limitation Talks, see disarmament, nuclear.

Strategic Air Command (SAC), former command of the U.S. air force (see Air Force, United States Department of the) charged with organizing, training, equipping, administering, and preparing strategic air forces for combat; it was headquartered at Offutt Air Force Base. From 1946 to 1992, SAC controlled most U.S. strategic nuclear weapons. Its bombers and guided missiles played a key role in the nuclear strategy of the cold war.

SAC was abolished in 1992 as part of the reorganization of the Department of Defense, and the Strategic Command was created. The Space Command was merged into the Strategic Command in 2002. The interservice Strategic Command, also based at Offutt, now coordinates nuclear plans for both the U.S. air force and navy and oversees all U.S. nuclear forces, conducts reconnaissance for strategic targets, oversees the radar and satellites that detect ballistic missile launches, and protects military computers and networks.

Office of Strategic Services (OSS), U.S. agency created (1942) during World War II under the jurisdiction of the Joint Chiefs of Staff for the purpose of obtaining information about enemy nations and of sabotaging their war potential and morale. Headed by William J. Donovan, the OSS comprised personnel from all the branches of the armed forces as well as civilians. Although the "cloak and dagger" section gained the most publicity after the war, some of the most valuable work was done by the research and analysis section. Behind enemy lines, the OSS acted as a liaison with the underground in Nazi-occupied countries. The OSS was disbanded in 1945. Later many of its functions were assumed by the Central Intelligence Agency.

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 ICBMs 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. Seealso antiballistic missile.

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Negotiations between the U.S. and the Soviet Union aimed at curtailing the manufacture of strategic nuclear missiles. The first round of negotiations began in 1969 and resulted in a treaty regulating antiballistic missiles and freezing the number of intercontinental ballistic missiles and submarine-launched ballistic missiles. It was signed by Leonid Brezhnev and Richard Nixon in 1972. A second round of talks (1972–79), known as SALT II, addressed the asymmetry between the two sides' strategic forces and ended with an agreement to limit strategic launchers (see MIRV). Signed by Brezhnev and Jimmy Carter, it was never formally ratified by the U.S. Senate, though its terms were observed by both sides. Subsequent negotiations took the name Strategic Arms Reduction Talks (START). Seealso intermediate-range nuclear weapons; Nuclear Test-Ban Treaty.

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