INTRODUCTION

Without doubt, in the past two decades, private military and security companies hired by a large number of entities have become important actors in both the international arena and domestic affairs of a large number of States. Many scholars agree that there are signs of a “revolution in military affairs”: nowadays, PMSCs freely operate around the world and take an active part in not merely peace support operations, but also international and non-international armed conflicts. They are frequently employed by States in the situations of armed conflict, by non-State entities participating in hostilities in internal conflicts, by international organizations in the course of conducting peacekeeping missions, and even by private companies paying large amounts of money for their military and security expertise. It is no secret that the concept of PMSCs as private corporations exercising core State functions has been around for longer than 20 years. Nowadays, the industry of private military and security specialists still shows signs of significant development and unprecedented growth. Currently, the world has to deal with many challenges posed by the emergence and proliferation of these companies. There are regulatory issues associated with the PMSC industry, transparency and legitimacy concerns raised against its representatives, problems of individual accountability and State responsibility for the actions of private warriors, who carry weapons, fight wars, and protect persons and assets of legitimate governments and other actors. Before going into the substance of the discussion focusing on the responsibility of States for the illegal conduct of those corporations, some attention should be devoted to the historical developments in the field of the use of force by private persons and entities.