Both the United States and the Soviet Union worked to develop ABM systems in the 1950s, generally using modified surface-to-air missile systems, such as the U.S. Army's Nike Zeus. ABM systems were viewed as a means of protecting valuable resources, including critical military forces and major cities, from destruction. As the technological challenges and cost of ABM operations became apparent and the size of strategic nuclear forces increased, the United States focused primarily on research and development and on improving early warning capabilities, relying on the deterrent effect of a strong nuclear retaliatory force to maintain security from nuclear attack. The Soviet Union deployed a limited system, the Galosh, around Moscow in the early 1960s and retained protection of the capital throughout the Cold War.
In the late 1960s, the United States announced that it would proceed with the Sentinel system to protect American cities from a limited attack by the Chinese. This system was eventually shifted to cover missile fields under the Safeguard program in an effort to gain greater stability for nuclear deterrence. Because of its high cost and technological glitches, Safeguard was only operational at one site in North Dakota for five months beginning in October 1975, although its Perimeter Acquisition Radar was integrated into the national early warning and attack assessment system. Concern over sustaining a stable deterrence posture was reflected in the 1972 Anti-Ballistic Missile Treaty that was negotiated along with the Strategic Arms Limitation Treaty (SALT I), which limited the United States and the Soviet Union to only two ABM sites (further limited to a single site each in a 1974 follow-up protocol).
President Ronald Reagan's administration sought to move away from the complete vulnerability to nuclear attack inherent in the mutual assured destruction (MAD) doctrine and to use new technological capabilities to build a national missile defensive system. This proposed system, called the Strategic Defense Initiative (SDI), eventually became known as "Star Wars" due to components that relied on space-based platforms and new types of weapons such as x-ray lasers to destroy missiles. Reagan argued that an operational ABM system would make nuclear missiles obsolete. After the collapse of the Soviet Union in 1991, the SDI concept was scaled back, although research and development efforts continued and options for protection against limited attacks, especially accidental launches or strikes by rogue states, became the justification for continuing to develop an ABM capability.
Jerome V. Martin
Graham, Bradley. Hit to Kill: The New Battle over Shielding America from Missile Attack. New York: Public Affairs, 2001.; Johnson, Nicholas L. Soviet Military Strategy in Space. London: Jane's Publishing, 1987.; Scott, Harriet Fast, and William F. Scott. The Armed Forces of the U.S.S.R. 4th ed. Boulder, CO: Westview, 2002.