The Strategic Defense Initiative (SDI), commonly called Star Wars after one of the popular science fiction movies of the time, was proposed by U.S. President Ronald Reagan on March 23, 1983Federation of American Scientists. http://www.fas.org/spp/starwars/program/milestone.htm Missile Defense Milestones. Accessed March 10, 2006. to use ground-based and space-based systems to protect the United States from attack by strategic nuclear ballistic missiles.