This text explores a transformational period in the history of the United Nations, one during which the attention of the organization became increasingly focused on North-South issues of colonialism, neo-imperialism, and the unequal distribution of global wealth. At the centre of this transformation stood U. Thant, the first secretary general to originate in the Third World and a leading spokesman for the interest of developing nations. Thant’s ten years as secretary general witnessed a series of new peacekeeping missions in Africa, Asia, and the Middle East and the establishment of institutional structures for the discussions of North-South economic issues. It also witnessed a recovery in the constitutional integrity of the office of secretary general, whose legitimacy had been attacked by the Soviet Union during the last year of the life of Thant’s gifted but troubled predecessor, Dag Hammarskjold.