The superpowers knew that these bombs could not be used against each other – to do so would destroy each other and would make the world uninhabitable. To the end of the Cold War the very existence of humanity lay in this fragile balance of deterrence, known as Mutually Assured Destruction or, rather aptly, MAD. The time had come to discuss how to slow down the arms race, and the first of many, rather meaningless, agreements came in 1963 with the signing of the Limited Test Ban Treaty.