Dan Plesch analyses the Global South’s role in disarmament. It offers evidence of a customarily ignored Southern agency in UN processes and suggests that the later work of Hans Morgenthau explains both this agency and contrary state policies. The article looks at the recent agreement with Iran as an example of constructive convergence and sets out the structure of an emerging and Southern-supported disarmament initiative. Dan Plesch is director of the Centre for International Studies and Diplomacy at SOAS, University of London. He is the author of America, Hitler and the UN, coeditor of Wartime Origins and the Future United Nations.