Because the world has firmly evolved from an offensive realism world in the past to a defensive realism world in which we live today, defensive realism is an appropriate guide for security strategy in our time. This book advances a coherent statement of defensive realism as a theory of strategy for our time. It adds to our understanding of defensive realism as a grand theory of IR in particular and our understanding of IR in general and contributes to the ongoing debates among major paradigms of international relations.