Human history could be framed by two eras – pre-nuke and post-nuke. The latter opened up on August 6 1945, and the world changed forever.
The US bombings of Hiroshima and Nagasaki in August 1945 initiated a new, terrifying phase in warfare. The potential to devastate an entire city with one bomb was now within the grasp of belligerent nations, and helpless fear of this fate underpinned Cold War tensions.
Nuclear weapons represented both a deterrent and a final resort to successive Presidents and Soviet leaders who sought to outmanoeuvre each other in building more and more warheads. It was felt that, should one dominate the other in this regard, then the war was effectively over. Had it not been for nuclear weapons, it is conceivable that the USA and the Soviet Union would have fought a direct, all-out war. Even with them, on a number of occasions a first-strike operation was contemplated by the US government.
Indeed the prevailing view among military leaders in the 1960s in particular was that war was inevitable and war should be conducted on their own terms, especially whilst the SA retained nuclear supremacy.