In this book, we will try to understand how AI has gradually been integrated into defence policies, strategies and doctrines, and, more specifically, into cybersecurity and cyber defence. This book is structured with chapters dealing with the history of AI (history of research, with which armies are closely associated, in some states), definitions of concepts (in what terms is AI mentioned? How does the military define AI and integrate it into its discourse?), policies (national cybersecurity strategies) and AI in military affairs (military strategies for AI, concepts, doctrines, cybersecurity and cyber defence, the different players). This book is a synthesis of current debates on the role of AI in defence affairs. Since AI is ?cyber? by nature, this book explores one dimension of the militarization of cyberspace. Is this renewed interest in AI the starting point for a reconfiguration of cyberspace, and for a new way of thinking about cybersecurity and cyber defence issues, cyber conflict and its multiple forms and manifestations? Are we moving towards a reconsideration of convictions hitherto held about the specific characteristics of cyberspace, such as its fluidity, the impossibility of establishing borders and the difficulty of marking or defending sovereignty, the impossibility of allocating actions, and the difficulty of controlling information? In this book, the reader will find numerous bibliographical references, (sometimes long) quotations and several summary tables, as we wanted to create a useful working tool for further developments.