In the earliest part of the cold war the United States enjoyed a clearly superior nuclear force to the Soviet Union but eventually nuclear parity was achieved and a new phase of the cold war had started. Realizing their vulnerability each side began producing nuclear weapons at a furious rate in an attempt to stay ahead of the other. The United States adopted a policy called Mutual Assured Destruction, a.k.a. MAD where protection for the population was achieved by ensuring the capability to utterly destroy the attacker if attacked. (Wilde)
This policy continued well in to the early 1980s until President Ronald Regan understanding the insanity of MAD proposed the implementation of a new policy called