Before 1945, the nations of the world could safely assume that any wars fought between them would be damaging but not annihilating. That changed with the deployment of the first atomic bomb on Hiroshima on August 6, 1945.

The nuclear era challenged previous assumptions about war and peace, as political leaders were forced to ponder how nuclear war could be fought, how it could be prevented, and what the meaning of victory, defense, and survival were. With the Cold War between the Soviets and Western nations growing, one key guiding principle became deterrence through strength, resulting in massive buildups of nuclear arsenals: enough weapons were present to destroy the world a thousand time over.