This timely volume analyses the impact of enlargement on both pre-existing EU security arrangements and key relationships with the EU's new partners and 'neighbours'. The changing nature of security, the enlargement of European institutions and the evolving functions of the EU have been key developments in post- Cold War Europe. This book blends these three crucial developments in a sophisticated and illuminating manner. EU enlargement is having both positive and negative implications for European security. This book provides a much-needed and comprehensive assessment of the impact of EU enlargement across the security spectrum. It embraces both hard and soft and internal and external security issues, ranging from military intervention to terrorism and from organised crime to human rights. Completing the analysis, it examines the evolving security relationships with key states, regions and international organisations in the EU's 'neighbourhood'. The examination of relations with Turkey, Russia, Ukraine, the Greater Middle East and the Balkans provides a sense of the direction in which European security politics is moving. Written by a blend of scholars and practitioners from across Europe, it highlights the fundamental security issues facing Europe in the twenty-first century. Central themes include the internal cohesion and external projection of EU security policy; the new security agenda; future enlargement and strategic relationships; crisis management operations; counter-terrorism and border security. This incisive volume fills a significant gap in the literature and will be an indispensable source for specialists and policy-makers and for students of international relations, security studies, European security and European politics.