Deudney et. al 11 [Daniel is associate professor of Political Science at John’s Hopkins University. Edited by Michael Mastanduno, Professor of Government and Dean of Faculty at Dartmouth College, and G. John Ikenberry, Professor of Politics and International Affairs at Princeton University, William Wolforth, the Daniel Webster Professor at Dartmouth College, where he teaches in the Department of Government, “Unipolarity and nuclear weapons” 2011 International Relations Theory and the Consequences of Unipolarity pg. 305]
The diffusion of nuclear weapons in the international system is significantly entangled with the role of the unipolar hegemonic state. The existence of a unipolar state playing the role of a liberal hegemon has arguably been a major constraint on the rate and extent of proliferation.The extended military alliance system of the United States has been a major reason why many potentially nuclear states have forgone acquisition. Starting with Germany and Japan, and extending to a long list of European and East Asian states, the American alliances are widely understood to provide a “nuclear umbrella.” Overall, without such a state playing this role, proliferation would likely have been much more extensive.
The liberal features of the American hegemonic sate also have contributed to constrain the rate and extent of proliferation. American leadership, and the general liberal internationalist vision of law-governed cooperative international politics, both enabled and infuses the non-proliferation regime. Similarly, therobust and inclusive liberal world trading system that has been a distinctive and salient feature of the American liberal hegemonic system offers integrating states paths to secure themselves that make nuclear acquisition less attractive.