With the advent of the Cold War in 1945 and the spread of nuclear weapons technology to the Soviet Union, the possibility of a third global conflict became more plausible. During the Cold War years, the possibility of a third world war was anticipated and planned for by military and civilian authorities in many countries. These scenarios ranged from conventional warfare to limited or total nuclear war. At the height of the Cold War, the doctrine of mutually assured destruction (MAD), which stipulated that an all-out nuclear confrontation would destroy all nations involved in the conflict, was developed. The potential for the utter destruction of the human species may have contributed to the ability of American and Soviet leaders to avoid such a scenario.