In his essay “Politics as a Vocation,” German sociologist Max Weber defined the state as “a human community that (successfully) claims the monopoly of the legitimate use of physical force within a given territory.” Central to a state's task, then, is controlling its territory, and promoting the impression that it is the only entity entitled to wield coercive power within its borders. But what happens when control over that territory is threatened? Under such circumstances, a state has several options. Often, these entail asking for help from other states, whether by calling on a powerful and well-armed ally or patron or by requesting assistance from a regional or transnational defensive body such as the United Nations. Alternatively, a state may choose to hire military forces from beyond its borders, voluntarily giving up its monopoly over the legitimate use of force, and extending that right to private individuals or corporations, known today as private military companies (PMCs).

Several types of private military companies coexist in the modern world. Some engage primarily in combat operations as a supplemental or substitute military force. These might operate against recalcitrant rebels, providing “better” or more high-tech weaponry than is available on the ground in the client state. Combat-oriented PMCs may also be hired to secure and protect mining or other valuable state-owned or commercial industries, and even by rebel groups in search of more effective military tactics.