This book explores the military strategies of the five system-determining great powers during the twenty-first century. The book’s point of departure is that analyses of countries’ defence strategies should acknowledge that states come in various shapes and sizes and that their strategic choices are affected by their perceptions of their position in the international system and by power asymmetries between more and less resourceful states. This creates a diversity in strategies that is often overlooked in theoretically oriented analyses. The book examines how five major powers – the United States, China, the United Kingdom, France and Russia – have adjusted their strategies to improve or maintain their relative position and to manage power asymmetries during the twenty-first century. It also develops and applies an analytical framework for exploring and categorising the strategies pursued by the five major powers which combines elements of structural realism with research on power transition theory and status competition. The concluding chapter addresses questions related to stability and change in the present international system. This book will be of interest to students of strategic studies, foreign policy, and International Relations.