This special issue explores military strategy in the twenty-first century. The articles scrutinise strategy from three perspectives: the study of strategy, and how our understanding of strategy has changed over time; new areas for strategic theory, i.e., areas where the development of war has made strategy become more important, such as peacekeeping operations and cyberspace;and the makers of strategy, more specifically why states choses suboptimal strategies and how wars in the twenty-first century influence strategy makers.