In 1928 the Briand-Kellogg Pact outlawed war. But it did not have any provisions that allowed the League of Nations to apply this principle; it was nothing more than a declaration of good intentions without any concrete agreement. It was signed by 63 states, none of which then or afterwards felt itself to be constrained in any way. It was only with the United Nations Charter, adopted in June 1945, that recourse to hostilities was subjected to the constraints of international law. By an appalling irony of history, atomic bombs were dropped a few weeks later on Hiroshima and Nagasaki.

Had the United States been in a position to have a monopoly on nuclear weapons, we would have found ourselves in an absurd but doubtless logical situation: on the one side the power of total destruction (a very embarrassing situation); elsewhere, nothing at all. On the other hand, had the United States decided to renounce nuclear weapons, and had some sort of world nuclear agency established a centralised store of nuclear material, there would be no such thing as proliferation. ‘If’ is a big word. All the issues we see cropping up again today were very seriously debated between 1945 and 1947. Many (but not all)⁽¹⁾ scientists at that time rejected any idea of a monopoly with horror. Were they right? They hoped that other states would also have military nuclear expertise; some went as far as to help the USSR. When the latter demonstrated that it was itself a nuclear power in 1948 the arms race was launched, opening a new era in thinking about disarmament.

The arrival of nuclear weapons gave a new impetus to the business of disarmament. It would henceforth take two separate directions.