While early private military and security companies (PMSCs) were likened to mercenaries, as of the 21st century, PMSCs have become regular actors in many nations and conflicts. Typically organized as legal corporate entities, they provide a wide range of military and security services, including transport, logistics, and maintenance to military and police training, demining, intelligence, risk analysis, armed and unarmed protective services, antipiracy measures, border protection, drones, and cyber operations. Not only have PMSC services diversified since the 1990s but so has their client base. Industrialized countries, autocratic regimes, failed states, international organizations, transnational corporations, and even humanitarian organizations hire PMSCs. There are several explanations for the rise of the industry. Functional explanations see the proliferation of PMSCs as a rational response to military capability gaps and increased demand for international security. Ideational and constructivist approaches attribute the outsourcing of military and security services to changing beliefs and norms about the appropriate relationship between states and markets. The consequences of using PMSCs for accountability, effectiveness, control, gender and racial equality, the location of political authority, and the provision of public and private security in conflict environments are key areas of research, as is the question of suitable forms of regulation for the industry, ranging from national and international laws to industry self-regulations, multistakeholder initiatives, and standard setting schemes. Finally, the privatization of military and security services raises concerns about a fundamental transformation in modern warfare.
