If pacifists are correct in thinking that war is always unjust, then presumably we ought to eliminate the possibility and temptation of ever engaging in it: We should not build war-making capacity, and if we already have, then demilitarisation—or military abolition—would seem to be the appropriate course to take. On the other hand, if war is sometimes justified, as most of us believe, then presumably it must be permissible to prepare for it by creating and maintaining a military establishment. On this view, in order for war-building to be justified, it is both necessary and sufficient that war-making be justifiable. But this view is mistaken. Even if war can be morally permissible on occasion, it does not follow that it is acceptable for any state to build and maintain an institution devoted to it. That is because militaries are exceedingly costly, not to mention dangerous, and there are going to be cases where these costs and risks are prohibitive. Obviously, there are large amounts of money at stake, but the true cost of a military cannot be captured in economic terms alone. This book explores the moral and social costs of militarisation, and shines a light on the ways in which a civilian population compromises its own security by having a war-machine attached to it.