The Strategic Defense Initiative (SDI) was an attempt by the USA to develop a defence system against incoming nuclear missiles, based in part outside the Earth’s atmosphere.
Nicknamed ”The Star Wars Program”, it was announced by President Reagan in March 1983, and by 1990 the research had cost over $16.5 billion.
The essence of the SDI was to attack enemy missiles at several different stages of their trajectory, using advanced laser and particle-beam technology, thus increasing the chances of disabling them.
Israel, Japan, and the UK are among the nations that assisted in SDI research and development. In 1988, the Joint Chiefs of Staff announced that they expected to be able to intercept no more than 30% of incoming missiles.
Some scientists maintained the program was unworkable and although SDI was scaled down in 1991 the USA was still working on a version of the Strategic Defense Initiative despite the end of the Cold War. In 1987 Gorbachev acknowledged that the USSR was developing a similar defence system.
A test of the proposed SDI missile defence system failed in January 2000, whereas a similar test in October 1999 was declared a success by the pentagon.
An increased emphasis was placed on limited defence, resulting in Global Protection Against Limited Strikes (GPALS), a program that would be capable of destroying only a few missiles aimed at the USA and its allies.
In 1993 the Clinton administration renamed the SDI Organization the Ballistic Missile Defense Organization (BMDO) to reflect its focus on defence against short-range missiles rather than long-range strategic missiles.
It was never truly developed or deployed, though certain aspects of SDI research and technologies paved the way for some anti-ballistic missile systems of today.
BMDO was renamed to the Missile Defense Agency in 2002.