This book contributes to the rethinking of realism through multiple analyses of the keys works of Kenneth Waltz, arguing that a sophisticated appreciation of realism is needed to truly understand world politics and International Relations. Bringing together a theoretically varied group of leading scholars from both sides of the Atlantic, this book is an outstanding appreciation of the work of realism's most important theorist since the Second World War, and the persistent themes thrown up by his work over a half-century. The contributors do not engage with Waltz's work as slavish disciples, but rather as positive critics, recognising its decisive significance in International Relations, while using the process of critical engagement to search for new or renewed understandings of unfolding global situations and new insights into long-standing problems of theory-building. The book will be of great interest to students of IR, foreign policy, security studies and politics.