This chapter introduces the major themes discussed throughout this book in a manner that emphasises both their relevance as well as the complexity of the international legal debates that surround them. It presents the central purpose of this book as unpacking R2P’s basis in international law and examining the doctrine’s application in the Libyan and Syrian cases. It furthermore outlines the distinct approach assumed within this book, including through its evaluation of the actions of a multitude of international actors in discharging R2P, its analysis of a diverse array of both military and non-military means by which the doctrine can be implemented, and its identification of gaps in R2P’s enforceability as well as how they can be overcome through the future development of international law. This chapter concludes with an overview of the book’s structure.