Short answers, pulled from the story.
The Strategic Defense Initiative was a proposed US missile defense system intended to protect the country from ballistic nuclear missile attack. President Ronald Reagan announced it on the 23rd of March 1983, calling on scientists to make nuclear weapons "impotent and obsolete."
The nickname traces to a Washington Post article published on the 24th of March 1983, quoting Senator Ted Kennedy, who had described the proposal the previous day as "reckless Star Wars schemes." The reference was to the space opera film franchise. President Reagan objected to the name, and SDIO officials called it a tool of Soviet disinformation.
In a report presented in 1986 and released publicly in early 1987, the American Physical Society concluded that all directed-energy weapon candidates required at least 100 times more power output, and in some cases up to a million times more, before they could be considered for missile defense. The panel found none of the systems could be deployed until the next century.
Brilliant Pebbles was a constellation of small, autonomous heat-seeking satellites designed to intercept ICBMs during their boost phase without relying on external guidance systems. Conceived in 1986 by Lowell Wood and Edward Teller, it was selected as the program baseline in 1990 and described by Lawrence Livermore director John H. Nuckolls as "the crowning achievement of the Strategic Defense Initiative." It was canceled in 1994.
The Soviet Union viewed SDI as a grave threat, fearing it could neutralize their nuclear arsenal and tip the strategic balance. Soviet commentators publicly argued it was an economic attack designed to bankrupt the USSR through a defensive arms race. Declassified CIA documents confirmed that Moscow threatened military countermeasures rather than building a parallel missile defense system.
SDI formally ended in 1993 when the Clinton administration renamed the Strategic Defense Initiative Organization the Ballistic Missile Defense Organization and shifted its focus to theater ballistic missiles. In 2002 the George W. Bush administration renamed it again as the Missile Defense Agency. Observational elements of SDI re-emerged in 2019 under the Space Development Agency.