Security Sector Reform (SSR) is increasingly becoming a cornerstone in international security and development cooperation. Indeed, the concept has often been seen as a panacea for many of the biggest threats to the world such as failed states, terrorism and poverty. In particular, this book focuses on the complexities of implementation of SSR across the globe and the actual and potential role for the European Union (EU) to play in SSR. As suggested in the title of the book, this involves not only opportunities, but challenges to be overcome as well. There are three core themes to this book: Policy, Policies and Practice. By presenting the themes in this particular order a greater appreciation of the influences on the process of SSR, from conception to implementation is relayed to the reader. This volume appeals to audiences interested in the EU as a global actor and the interrelationships between foreign, security, defence and development policies.