sample post wikidepia

Nike-X was an anti-ballistic missile system developed in the 1960s by the US Army to counter the Soviet Union's intercontinental ballistic missiles (ICBM). Tested but never deployed, it was a response to the problems with Nike Zeus, whose radars could not tell the difference between warheads and decoys until it was too late to launch. Nike-X would wait until the last moment and launch a very fast missile known as Sprint (pictured); the entire engagement would last only a few seconds, at altitudes as low as 25,000 feet (7.6 km). While technically capable, a Nike-X missile would have been very expensive, as much as 20 times the cost of the ICBM at which it was fired. Robert McNamara, the Secretary of Defense, felt the Soviets would respond by building more ICBMs, leading to a new nuclear arms race. In 1967, Nike-X was cancelled in favor of a simpler system, Sentinel.

source: wikipedia