On March 23, 1983, President Reagan proposed the creation of the Strategic Defense Initiative (SDI), an ambitious project that would construct a space-based anti-missile system. This program was immediately dubbed "Star Wars."

An artist's rendering of an X-ray laser hit an incoming missile.

The SDI was intended to defend the United States from attack from Soviet ICBMs by intercepting the missiles at various phases of their flight. For the interception, the SDI would require extremely advanced technological systems, yet to be researched and developed. Among the potential components of the defense system were both space- and earth-based laser battle stations, which, by a combination of methods, would direct their killing beams toward moving Soviet targets. Air-based missile platforms and ground-based missiles using other non-nuclear killing mechanisms would constitute the rear echelon of defense and would be concentrated around such major targets as U.S. ICBM silos. The sensors to detect attacks would be based on the ground, in the air, and in space, and would use radar, optical, and infrared threat-detection systems.

This system would tip the nuclear balance toward the United States. The Soviets feared that SDI would enable the United States to launch a first-strike against them. Critics pointed to the vast technological uncertainties of the system, in addition to its enormous cost.

Although work was begun on the program, the technology proved to be too complex and much of the research was cancelled by later administrations. The idea of missile defense system would resurface later as the National Missile Defense.