Strategic Defense Initiative

Strategic Defense Initiative (SDI), controversial program developed by the U.S. government in 1983 to develop a space-based shield against nuclear missile attack. Commonly called “Star Wars,” the program was to rely on satellites and lasers to destroy incoming missiles. Its opponents argued that it was impractical and costly. Funding for research on the project continues, although at a reduced rate. Part of the program has been replaced by GPALS, Global Protection Against Limited Strikes.