The use of private military force by states has been a long-standing phenomena in the history of warfare. Armies of mercenaries, privateering and recruitment of foreign nationals into armed forces have been common during the Middle Ages and later on. However, with the invention of effective firearms and artillery, standing regular armies, conscription and other developments that resulted in the essential rise of costs of war, the role of private military entrepreneurs diminished. By the end of XIXth century the state (...) became almost the only subject that was able to wage a full-scale war. Nevertheless, already in the middle of the XXth century mercenarism has been reborn in Africa’s colonial and post-colonial wars. The end of the XXth century and the beginning of the XXI century witnesses an enormous rise of private security and military companies (PSMC) that are hired to perform different functions related to use of force not only by states, but also by other clients such as international organisations, transnational corporations, etc. A PSMC may be defined as a profit-seeking private enterprise, which is established according to the national law of the state and which is providing, on the basis of a contract, services directly or indirectly connected with the use of military force or its institutions whether in time of armed conflict or peace, notwithstanding how such company describes itself. International humanitarian law has no specific regulation of PSMC. Nevertheless, it would be erroneous to state that the activity of PSMC is not regulated, because international humanitarian law in any case, in one or another way, is applicable to the personnel of PSMC if it is engaged in armed conflict of either international or non-international character. (shrink)