1949 - Soviets explode their first nuclear bomb; Cold War rivals begin nuclear arms race.

1950s - Soviet competition for power with West extends into Latin America and former European colonies in Africa, making Cold War global.

1953 - Death of Stalin ushers in less repressive rule at home, although Communist Party political dominance is firmly upheld.

1957 - Soviet artificial satellite Sputnik becomes first to orbit Earth, spurring the Cold War beyond the atmosphere in a Space Race.

1962 - Cuban Missile Crisis brings world to brink of nuclear war; perceived defeat for Soviet leader Nikita Khrushchev hastened his ouster two years later by more conservative faction, eventually led by Leonid Brezhnev.