This new book tackles two key questions: 1) How is the EU functioning as a security actor? 2) How and to what extent is the EU affecting national security identities? Focusing on the four largest Nordic states (Denmark, Finland, Norway and Sweden), this incisive study analyzes how and to what extent the EU affects national security identities. It shows how the EU has developed into a special kind of security actor that, due to its level of political integration, has an important influence on national security approaches and identities. This new analysis applies a fresh combination of integration theory, security studies and studies of Europeanization. The main argument in this book is that, rather than adapting to the changing conditions created by the end of the Cold War, the Nordic states changed their security approaches in response to the European integration process. It shows how different phases in the post Cold War European integration process have influenced the national security approaches of Sweden, Finland, Denmark and Norway. While all four security approaches seem to have been Europeanized, the speed and the character of these changes seem to vary due to a combination of differing ties to the EU and differing security policy traditions. This new book will be of great interest to all students of European Defence, national security and of security studies in general.