This book examines the causes and consequences of the Ukraine crisis, with a special focus on Russia’s relations with the West. Towards that end, it brings together international relations scholars and area specialists. Issues covered include: the evolution of EU–Russia and US–Russia relations, the role of strategic culture and ontological insecurities in the formation of Russian foreign policy, the role of hybrid warfare in Russian military policy, the geopolitical drivers of Russia’s Ukraine policy, and a discussion of the decision-making dynamics that led to Russia’s intervention in eastern Ukraine. The contributors employ different theoretical approaches and offer partly complementary and partly competing analyses. In so doing, this book seeks to stimulate dialogue between different positions and advance our understanding of a topic that will shape the European security order for many years to come. This book was originally published as a special issue of Contemporary Politics.