LIM-49 Nike Zeus

Nike Zeus was an anti-ballistic missile (ABM) system developed by the US Army during the late 1950s and early 1960s, designed to destroy Soviet Intercontinental ballistic missile warheads before they could hit targets in the United States. It was designed by Bell's Nike team, and was initially based on the earlier Nike Hercules anti-aircraft missile. The original Zeus A, given the tri-service identifier XLIM-49, was designed to intercept warheads in the upper atmosphere, mounting a 25 kiloton W31 nuclear warhead to guarantee a kill. During development it was greatly enlarged and extended into a totally new design, Zeus B, intended to intercept warheads over a much larger area, and mounting a 400 kiloton W50 warhead. In several successful tests, the B model proved itself able to intercept warheads, and even satellites.

The nature of the strategic threat changed dramatically during the period that Zeus was being developed. Originally expected to face only a few dozen ICBMs, a nationwide defense was feasible, although expensive. In 1957, growing fears of a Soviet sneak attack led it to be repositioned as a way to protect Strategic Air Command's bomber bases, ensuring a retaliatory strike force would survive. But when the Soviets claimed to be building hundreds of missiles, the US faced the problem of building enough Zeus missiles to match them. The Air Force suggested they close this missile gap by building more ICBMs of their own instead. Adding to the debate, a number of technical problems emerged that suggested Zeus would have little capability against any sort of sophisticated attack.

LIM-49 Spartan

The LIM-49A 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 deployment, a defensive five-megaton atomic warhead was planned to destroy the incoming ICBM. It was part of the Safeguard Program.

Spartan was the ultimate 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' 250 miles (400 km) to about 450 miles (720 km).

Spartan was initially developed as part of 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.