History · A Level: The nuclear arms race, 1945-1991 (exams to Nov 2026). The idea in plain words, the rules to remember, the mistake to avoid and a worked example, written and checked by Mega Lecture.
The USA had the only atomic bombs from 1945 until the USSR tested its own in 1949. Each side then tried to stay ahead. The far more powerful hydrogen bomb, which uses nuclear fusion, followed in the early 1950s.
The race then moved to delivery systems: from bombers to ICBMs, to missiles fired from submarines, and to MIRVs, where one missile carries several warheads. Sputnik in 1957 made Americans fear they were falling behind.
Strategy changed as weapons changed. Once both sides could survive an attack and still hit back, neither could win a nuclear war. This is Mutually Assured Destruction.
Students often describe the 'missile gap' as a real Soviet lead. It was a mistaken fear: U-2 flights and later satellites showed the USA had more missiles.
Answer: ICBMs cut warning time to minutes and could not be recalled, so each side feared a sudden first strike and built more weapons to be safe.
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