The Treaty of Lisbon was in fact a milestone in the process of expanding the EU's role on the level of international security. It stipulated in the Treaty on the European Union that the principal aspect of EU security is a mutual defense clause designed to protect all member states. The book aims to show the changes that are taking place in the EU as a result of the ongoing globalization and of the emergence of non-traditional threats in the securitization process. Therefore, this book was written with the aim of analyzing the current nature of the EU as a regional security complex (RSC), following the implementation of the Treaty of Lisbon, as well as with the aim of revising all elements of this integrated security area contemporarily using the methodology of Barry Buzan and Ole Wæver.