Following World War II, the Soviet Union's occupation of Eastern Europe (the Soviet Bloc) led to fears in Western Europe and the United States. In response, Western nations formed NATO in 1949 as a mutual defense alliance against the Soviets. Not to be outdone, the Soviets countered with the Warsaw Pact in 1955. Both alliances stipulated that an attack on one member would be considered an attack on all, significantly escalating Cold War tensions.

The Cold War fueled a nuclear arms race between the US and the Soviet Union. After the US developed the atomic bomb, the Soviets created their own in 1949. This led to a rapid escalation, with both superpowers developing more powerful hydrogen bombs, accumulating enough weaponry to destroy the world multiple times over. The peak of this crisis was the 1962 Cuban Missile Crisis, where Khrushchev placed nuclear missiles in Cuba, leading to a tense naval blockade by the US. This near-catastrophe highlighted the dangers of nuclear proliferation and led to the Nuclear Non-Proliferation Treaty in 1968, aiming to prevent the spread of nuclear weapons.

Due to the 'cold' nature of the war, direct conflict between the superpowers was avoided, but indirect 'proxy wars' raged across Africa, Asia, and Latin America. These local conflicts gained global significance as the US and Soviets supported opposing sides. Examples include the Korean War (1950-1953), where communist North Korea invaded anti-communist South Korea, drawing in US and Soviet support. The Angolan Civil War (1975 onwards) saw the US, Soviets, and South Africa backing different ethnic groups in post-colonial Angola. Lastly, the Contra War in Nicaragua (1979 onwards) involved US-backed Contras attempting to overthrow the Soviet-supported Sandinista socialist government. These proxy wars allowed the superpowers to battle indirectly, often with devastating consequences for the local populations.