Challenging views that have gained currency since the end of the Cold War, this study examines the history of the United Nations since 1945, its various roles in international relations and its approaches to peace-keeping and the use of force. The authors provide a basis for courses and debates on the UN. Appraising the organisation's past performance and future potential - and avoiding the fault of piety, as well as that of UN-bashing - they suggest that the United Nations can be most effective if there is frank recognition of the limits imposed on it by the heterogeneous international society within which it operates.