Fox coined the word "superpower" in his 1944 book "The Super-Powers: The United States, Britain, and the Soviet Union – Their Responsibility for Peace" to identify a new category of power able to occupy the highest status in a world in which, as the war then raging demonstrated, states could challenge and fight each other on a global scale. According to him, there were (at that moment) three states that were superpowers: the United States, the Soviet Union, and the British Empire. The book forecast the directions that Soviet-American relations would take if the powers did not collaborate, but also made an effort to explore feasible opportunities that leaders might have to forestall that future. Fox was part of the international staff at the 1945 United Nations Conference on International Organization, the San Francisco meeting that led to the creation of the United Nations Charter. He was one of the contributors to Bernard Brodie's landmark 1946 volume "The Absolute Weapon: Atomic Power and World Order", where he recognized with Brodie that the future nuclear stand-off between the U.S. and U.S.S.R. would become focused on the fear of mutual destruction, but in his portion explored ways that international agreements to limit or control nuclear weapons might improve matters. Fox came away from his activities during this period convinced that the framing of international relations theory should be around the proposition that, "If man is to have the opportunity to exercise some measure of rational control over his destiny, the limits of the possible and the consequences of the desirable both have to be investigated."