This book highlights how temporary international civil servants play a crucial role in initiating processes of legal and institutional change in the United Nations system. These individuals are the "missing" creative elements needed to fully understand the emergence and initial spread of UN ideas such as human development, sovereignty as responsibility, and multifunctional peacekeeping. The book: Shows that that  temporary UN officials are an actor category which is empirically crucial, yet usually neglected in analytical studies of the UN system. Focussing on these particular individual actors therefore allows for a better understanding of complex UN decision-making. Demonstrates how these civil servants matter, looking at what their agency is based on. Offering a new and distinctive model, Bode seeks to move towards a comprehensive conceptualisation of individual agency, which is currently conspicuous for its absence in many theoretical approaches that address policy change Uses three key case studies of  international civil servants (Francis Deng, Mahbub ul Haq and  Marrack Goulding) to explore the possibilities of this specific group of UN individuals to act as agents of change and thereby test the prevailing notion that international bureaucrats can only act as agents of the status quo . This book will be of great interest to students and scholars of international organizations and the United Nations.