The Missile Gap is a term used for the perceived disparity between the power and weapons of the USSR during the Cold War. The estimates originally released suggested that the Soviets could have 1000's of ICMB's in a few years, and that the US was way behind when it comes to bombs. Even though there was never any physical proof that the Soviets had that many weapons, the US Government used it as a political tool in order to let a massive expansion of spending and authoritarian cold war measures that may otherwise have been impossible to justify to the voters.
On the 4th of October 1957, the soviets launched the first ever artificial satellite to be put into earths orbit. This highlighted the technological achievements of the Soviets and made the United States start to worry about what else the USSR has accomplished. Later that year The National Intelligence Estimate predicted that the Soviets would probably first operational capability with up to 10 prototype ICMB's sometime between mid-1958 to mid-1959. The USSR leader, Nikita Khrushchev, claimed to be producing missiles "like sausages" which didnt help Americas growing fear.
A few months after, the National Intelligence Estimate said, "the USSR had 'the technical and industrial capability ... to have an operational capability with 100 ICBMs' some time in 1960, and perhaps 500 ICBMs 'some time in 1961." These estimates were not based on any information or intelligence received, just guesswork. In 1956 a U-2 spy plane flew over the USSR and took pictures of the soviets 'progress'. These images proved that the number released from the National Intelligence Estimate were way off, after the pictures were taken the CIA placed the number of Soviet ICMB's at about a dozen. It is known today that even the CIA's estimate was too high; the actual number of ICBMs, even including prototypes, was 4.
