This book is a diplomatic history of Europe and the wider world over a period of 500 years, from the beginning of the sixteenth century to the early twenty-first century - with a crucial aspect. The book reflects upon the development of diplomacy and diplomats in changing from acting solely in the national interests of their respective countries to increasingly engaging in international conflict resolution and peace-making. It will be an invaluable reading for students and practitioners of international history, international relations and international security.