This book utilises three theoretical models to analyse the defence conditions and preparedness of all the states of Eastern Europe. It considers the transition from Cold War communism to post-Cold War democracies, the stability of the East-Central European States, the precarious defence positions of the Baltic states and the uneven defence preparedness of the Balkan states. Following the passage of the fifteenth and twentieth anniversaries of the entry of many former communist states into both NATO and the EU in 2019, this book takes a comprehensive look at the changed security conditions of these new member states. How has NATO and EU membership improved their overall defence protection, and what elements are still missing for them on an individual state basis? Utilising alliance politics theory, convergence/divergence theory and defence policy theory, the book provides an invaluable assessment of defence policies, from the stable East Central European states to the most jeopardised Baltic states in the north of Europe. With chapters on the Cold War defence conditions during the last two decades of Soviet domination, post 1989–91 transformations in the direction of democracy and the impact of the 2014 Ukraine–Russia–Crimea crisis, this book is essential reading for those seeking to understand the changed landscape of European politics in the twenty-first century.