The Cold War featured an intense offensive and defensive strategic arms race between the U.S. and the Soviet Union that included nuclear weapons, Intercontinental Ballistic Missiles (ICBMs) and missile defense systems. The theory that defensive armament would result in an offensive arms race to penetrate existing missile defense systems prompted both sides to sign the 1972 Anti-Ballistic Missile Treaty (ABM Treaty). That treaty allowed only two missile defense systems to protect limited areas, later reduced to only one system through the additional Protocol to the Treaty in 1974. However, neither the U.S. nor the Soviet Union stopped their efforts to develop missile defense systems. The Strategic Defensive Initiative (SDI), known as Star Wars and introduced by President Reagan in 1983 became one of the largest military projects in U.S. history; however, it was canceled after intense debate over feasibility and cost.
The U.S. dream of a missile shield to protect the North American continent from any range of the ballistic missile, especially Russian and Chinese ICBMs equipped with nuclear warheads, never disappeared. America intensified its efforts on the National Missile Defense (NMD) project after President George W. Bush announced in 2002 that the U.S. would withdraw from the ABM Treaty, with the deployment of advanced interceptors in Alaska and California to protect the U.S. continent against intermediate- and long-range missiles becoming a cornerstone of the project. The U.S. also announced that it would deploy ten Ground-Based Interceptors (GBIs) in Poland and a fixed radar system in the Czech Republic, as part of the NMD.