This book delves into the profound implications of Russia’s war against Ukraine for both the European Union (EU) and the field of EU Studies. It systematically addresses three overarching themes. 1) The Evolution of Theories and Approaches: This volume scrutinises how the ongoing war reshapes the landscape of EU Studies and how the war against Ukraine is received and discussed within the realm of EU and International Relations Studies. It rigorously examines the far-reaching consequences of the war on established theoretical frameworks, approaches and conceptual paradigms in both academic disciplines. 2) The Transforming EU Polity and Its Policies: An in-depth analysis unfolds the multifaceted impact of the war on the EU, spanning its external and internal dynamics. Particular attention is devoted to the intricate interplay between democracy and autocracy, the challenges surrounding the rule-of-law and the complex intersections of energy security, sustainability and emergency governance. 3) Ukraine’s EU accesion: Within the context of the war, this book explores the prospects, conditions and timing of Ukraine’s potential accession to the EU. It delves into the shifting narratives surrounding Ukraine, scrutinises perceptions of the EU’s role as a ‘normative power’ and assesses the extent to which the EU can assert this identity amidst contestations over accession conditions. Furthermore, it probes the evolving global perceptions of Ukraine and the war amidst a dynamic and shifting world order. In the introduction, we will sketch these problem fields, delving into their intricacies and indicating the answers given within the pages of this book.