With the advent of the Cold War in 1945 and with 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 civil authorities in many countries. Scenarios ranged from conventional warfare to limited or total nuclear warfare. At the height of the Cold War, a scenario referred to as Mutually Assured Destruction ("MAD") had been calculated which determined that an all-out nuclear confrontation would most certainly destroy all or nearly all human life on the planet. The potential absolute destruction of the human race may have contributed to the ability of both American and Soviet leaders to avoid such a scenario.