In contemporary, late-modern society, security landscapes are being re-sketched. Various traditional and new security providers are part of this evolving scene. The military and the police, who are thought of as 'the old boys in town', are meeting once again. As central components in the power structure of any state, they are heavily involved in this new security design, generating both latent and obvious blurring of boundaries.The aim of this book is to further explore the blurring boundaries between the military and the police from different perspectives without pretending to be exhaustive in any way. We present historical contexts, concepts, implications, challenges and cases. In this fascinating area of research, which is perpetually in motion and constantly changing in nature and the ways it manifests itself, this book offers some explorations and reflections which can be elaborated in the future.This book is a mutual initiative of the research group 'Governing & Policing Security' of the University College Ghent & the Netherlands Defence Academy in close collaboration with the Faculty of Social Sciences of the VU University Amsterdam and the research group 'International Research on Criminal Policy' of the Ghent University.