The LIM-49 Spartan was a United States Army anti-ballistic missile, designed to intercept attacking nuclear warheads from Intercontinental ballistic missiles at long range and while still outside the atmosphere. For actual deployment, a five-megaton thermonuclear warhead was planned to destroy the incoming ICBM warheads. It was part of the Safeguard Program. The Spartan was the latest and, as it turned out, final development in a long series of missile designs from the team of Bell Laboratories and Douglas Aircraft Company that started in the 1940s with the Nike. Spartan was developed directly from the preceding LIM-49 Nike Zeus, retaining the same tri-service identifier, but growing larger and longer ranged, from the Zeus' to approximately . The Spartan was superseded by the Nike-X project, later becoming the Sentinel Program. This was eventually cancelled and replaced with the much smaller Safeguard Program. Spartans were deployed as part of the Safeguard system from October 1975 to early 1976. History Zeus The US Army started their first serious efforts in the anti-ballistic missile arena when they asked the Bell Labs missile team to prepare a report on the topic in February 1955. The Nike team had already designed the Nike Ajax system that was in widespread use around the US, as well as the Nike Hercules that was in the late stages of development as the Ajax's replacement. They returned an initial study on Nike II in January 1956, concluding that the basic concept was workable using a slightly upgraded version of the Hercules missile, but requiring dramatically upgraded radars and computers to handle interceptions that took place at thousands of miles an hour. Work began on the resulting LIM-49 Nike Zeus system in January 1957, initially at a low priority. However, several developments that year, including the development of the first Soviet ICBMs and the launch of Sputnik I, caused the schedule to be pushed up several times. In January 1958 Zeus was given "S-Priority", the highest national priority, with aims to deploy the first operational sites in 1963. To test the system fully, the Army took control of Kwajalein Island from the US Navy, and began building an entire Zeus site on the island. By 1962 the system was ready for testing, and after some initial problems, demonstrated its ability to intercept warheads launched from California. Eventually fourteen "all up" tests were carried out over the next two years, with ten of