This introduction provides an overview of the key concepts discussed in the subsequent chapters of this book. The book introduces the theoretical framework proposed, explaining the relationships, variables and mechanisms at work. It applies the framework to the empirical case of United Nations High Commissioner for Refugees (UNHCR), introducing the relevant forced migration literature on UNHCR's surrogate statehood and providing some background to UNHCR's history, its "toolbox" of influence over states and its operational presence. The book provides case studies of UNHCR's surrogacy, looking at its role and varied levels of influence in Kenya, Tanzania and Uganda. It concludes the study by pulling together overarching themes, considering the findings in light of the framework and drawing out areas for further research. The book shows how an international organizations' (IOs) role at the domestic level, with a physical presence in a given locale, can affect state behavior.