Drawing on NATO's past, present and future, Sean Monaghan combines history, strategic theory and future analysis to shed light on how NATO's deterrence strategy has evolved over the past 75 years and how it will need to adapt over the next 75. For over seven decades, NATO, the world's largest and most successful military alliance, has helped prevent war breaking out again in Europe. This timely and accessible book examines the state of NATO's deterrence strategy in the wake of perhaps the biggest challenge in its history: Russia's brutal invasion of Ukraine. Exploring how allied deterrence is being tested in new ways, with the emergence of new superpowers, including China, and new modes of warfare including non-military hybrid and cyber threats, this book demonstrates how NATO's deterrence strategy should adapt to these challenges.