The Strategic Defense Initiative (SDI), commonly called Star Wars after the popular science fiction movies of the time, was proposed by U.S. President Ronald Reagan on March 23, 1983 to use ground-based and space-based systems to protect the United States from attack by strategic nuclear ballistic missiles. The initiative focused on strategic defense rather than the previous strategic offense doctrine of Mutual assured destruction (MAD). Though it was never fully developed or deployed, the research and technologies of SDI paved the way for some Anti-ballistic missile systems of today. The Strategic Defense Initiative Organization (SDIO) was set up in 1984 within the United States Department of Defense to the Strategic Defense Initiative. Under the administration of President Bill Clinton in 1993, its name was changed to the Ballistic Missile Defense Organization (BMDO) and its emphasis was shifted from national missile defense to theater missile defense, i.e. from global to regional coverage. This article covers defense efforts under the SDIO.

Strategic missile defense prior to SDI

SDI was not the first U.S. defensive system against nuclear ballistic missiles. In the 1960s, The Sentinel Program was designed and developed to provide a limited defensive capability, but was never deployed. Sentinel technology was later used in the Safeguard Program, briefly deployed to defend a single U.S. location. In the 1970s the Soviet Union deployed a missile defense system, still operational today, which defends Moscow and nearby missile sites.

SDI is unique from the earlier U.S. and Soviet missile defense efforts. It envisioned using space-oriented basing of defensive systems vs solely ground-launched interceptors. It also initially had the ambitious goal of a near total defense against a massive sophisticated ICBM attack, vs previous systems which were limited in defensive capacity and geographic coverage, and oriented toward a lertarser attack.

Initial Impetus

In the fall of 1979, at Reagan's request, Lieutenant General Daniel O. Graham conceived a concept he called the High Frontier, a concept of strategic defense using ground and space based weapons theoretically possible because of emerging technologies. It was designed to replace the doctrine of Mutual assured destruction, a doctrine that Reagan and his aides described as a suicide-pact.

The initial focus of the strategic defense initiative was a nuclear explosion powered X-ray laser designed at Lawrence Livermore National Laboratory by a scientist named Peter Hagelstein who worked with a team called O Group, doing much of the work in the late 1970s and early 1980s. O Group was headed by physicist Lowell Wood, a protégé and friend of Edward Teller, the "father of the hydrogen bomb".