The Soviet launch of Sputnik 1 on the 4 October, 1957 highlighted the technological achievements of the Soviets and sparked some worrying questions for the politicians and general public of the USA. John F. Kennedy stated "the nation was losing the satellite-missile race with the Soviet Union because of ... complacent miscalculations, penny-pinching, budget cutbacks, incredibly confused mismanagement, and wasteful rivalries and jealousies." The Soviet lead was due mostly to the US having suitably forward basing in Europe and Turkey, allowing them to concentrate on much shorter-range, smaller IRBMs. The Soviets, lacking suitable overseas bases, were forced to move directly to the much larger and technically daunting ICBM, which made them more suitable for space launches.
The National Intelligence Estimate (NIE) 11-10-57, issued in December 1957, predicted that the Soviets would "probably have a first operational capability with up to 10 prototype ICBMs" at "some time during the period from mid-1958 to mid-1959." After Khrushchev claimed to be producing them "like sausages", the numbers started to inflate. A similar report gathered only a few months later, NIE 11-5-58 released in August 1958, concluded that 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, or at the latest in 1962." None of these estimates were based on anything other than guesswork.
Beginning with the collection of photo-intelligence by U-2 overflights of the Soviet Union in 1956, the Eisenhower administration had increasing hard evidence that claims of any strategic weapons favoring the Soviet Union were false. Based on this evidence, the CIA placed the number of ICBMs closer to a dozen. Continued (sporadic) flights failed to turn up any evidence of additional missiles. Curtis LeMay argued that the large stocks of missiles were in the areas not photographed by the U-2's, and arguments broke out over the Soviet factory capability in an effort to estimate their production rate.
It is known today that even the CIA's estimate was too high; the actual number of ICBMs, all interim-use prototypes, was four.
Later evidence has emerged that one consequence of Kennedy pushing the false idea that America was behind the Soviets in a missile gap was that Soviet premier Nikita Kruschev and senior Soviet military figures began to believe that Kennedy was a dangerous extremist who, with the American military, was seeking to plant the idea of a Soviet first-strike capability to justify a pre-emptive American attack. This belief about Kennedy as a militarist was reinforced in Soviet minds by the Bay of Pigs invasion of 1961 and led to the Soviets placing nuclear missiles in Cuba in 1962.
Warnings and calls to address imbalances between the fighting capabilities of two forces were not new, a "bomber gap" had exercised political concerns a few years previously. What was different about the missile gap was the fear that a distant country could strike without warning from far away with little damage to themselves. Concerns about missile gaps and similar fears, such as nuclear proliferation, continue, with most recently the aggressive missile testing between India and Pakistan.
A second claim of a missile gap appeared in 1974. Albert Wohlstetter, a professor at the University of Chicago, accused the CIA of systematically underestimating Soviet missile deployment, in his 1974 foreign policy article entitled "Is There a Strategic Arms Race?" Wohlstetter concluded that the United States was allowing the Soviet Union to achieve military superiority by not closing a perceived missile gap. Many conservatives then began a concerted attack on the CIA's annual assessment of the Soviet threat.
This led to an exercise in competitive analysis, with a group called Team B being created with the production of a highly controversial report.