Since the start of the twenty-first century, military contractors such as Blackwater (now named Academi), Kellogg, Brown & Root, and SNC Lavalin have become household names in many countries. The reasons for their prominence vary from case to case. One is notoriety. Particular firms hold contracts valued in the millions if not billions of dollars, and the conduct of some firms has not been beyond reproach in terms of military effectiveness or their observance of human rights. A second reason is reliance. Contractors are needed to keep state military personnel fed and supplied, to maintain their machines, and in some cases even to protect them. Developed world states especially require them for warring, training, and simply operating given the limited numbers of available national military personnel, the increasing sophistication of military technologies, and the political ramifications of applying state forces overseas. In many states, contractors have therefore become part of the total national force. Yet another reason pertains to dedication and sacrifice. Many firms suﬀffered significant levels of casualties during the long-term interventions in Iraq and Afghanistan. Thousands of contracted personnel have provided continuity over the long haul in often austere and intemperate conditions. All of this points to the considerable depth and scope of contractor involvement, which is arguably unprecedented in recent decades if not centuries. It also stands at odds with traditional conceptions of expensive state security sectors and their capabilities and responsibilities to manage and apply violence.
Charles A. Kupchan has written an important book that poses fundamental questions for international relations scholars and policy makers: First, how do enemies in world politics become friends? Specifically, through what pathways can pairs or groups of states succeed in setting aside their geopolitical competition and construct enduring relationships that preclude the possibility of armed conflict? Second, when and why do enemies become friends (and vice versa)? In other words, under what circumstances are such zones of peace more likely to form and under what circumstances are they likely to dissolve?