Gazes into the crystal ball to forecast what the future of war looks like in a world dominated by private armies. The way war is waged is evolving quickly--igniting the rapid rise of private military contractors who offer military-style services as part of their core business model. When private actors take up state security, their incentives are not to end war and conflict but to manage the threat only enough to remain relevant. Arduino unpacks the tradeoffs involved when conflict is increasingly waged by professional outfits that thrive on chaos rather than national armies. This book charts the rise of private military actors from Russia, China, and the Middle East using primary source data, in-person interviews, and field research amongst operations in conflict zones around the world. Individual stories narrated by mercenaries, military trainers, security entrepreneurs, hackers, and drone pilots are used to introduce themes throughout. Arduino concludes by considering today's trajectories in the deployment of mercenaries by states, corporations, or even terrorist organizations and what it will mean for the future of conflict. The book follows private security contractors that take on missions in different countries with a variety of challenges. First-hand data and intimate knowledge of the actors involved in the market for force allow a fully grounded narrative with personal input. Through this prism, readers will gain a better understanding of the human, security, and political risks that are part of this industry. The book specifically reveals the risk that unaccountable mercenaries pose in increasing the threshold for conflict, the threat to traditional military forces, the corruption in political circles, and the rising threat of proxy conflicts in the US rivalry with China and Russia.