The Introduction presents an overview of the chapters of the book to show the enduring influence of the Monroe Doctrine on the formulation and execution of American foreign policy relative to the American hemisphere since 1823. It explores the management of international relations by the Great Powers from 1815 to 1914 and their relationship with small states in the community of nations; the process of decolonialisation following the Second World War and the new political dynamics created by the assemblage of a large number of newly independent states in the United Nations system; their endorsement of a number of key principles, including sovereignty, territorial integrity, self-determination and peaceful co-existence to assert their national independence as well as the rivalry between the United States and the Soviet Union for influence in the developing world, notably the Western Hemisphere. The author has examined the efforts of regional states to consolidate their national independence and attempts by United States policymakers to apply the tenets of the Monroe Doctrine, in cases of political instability, to promote or defend the country’s national or geostrategic interests.