Bipolarity was viewed both as an empirical condition and as a central explanatory concept, albeit contested, during the Cold War (1945–1989), when two superpowers dominated the international system. The United States and the Union of Soviet Socialist Republics (USSR) confronted each other as military and ideological rivals heading competing alliance systems—the North Atlantic Treaty Organization (NATO), founded in 1949, and the Warsaw Pact established in 1955. Nuclear weaponry added a new wrinkle to the global superpower competition, particularly after the Soviet Union broke the American nuclear monopoly in 1949. A rich literature around these themes emerged as scholars sought to grapple with the explanatory dynamics propelling state behavior under the systemic constraints of bipolarity and the technological challenges presaged by the nuclear age. Such an academic focus meant that the study of international politics, particularly in the United States, was largely refracted through the prism of U.S.-Soviet competition and centered on the nature and implications of polarity, power, alliances, and nuclear deterrence. When the Soviet Union imploded, bipolarity in the sense of two predominant powers ended, as did the division of the world into two opposing blocs. In the post-Cold War period, scholars turned their attention to investigating questions regarding the impact on the nature of system structure and the international order of the collapse of one of the poles. Accordingly, during the Cold War, scholars debated the conceptual and empirical understandings of bipolarity as well as its implications and the causal factors on which the expectation of bipolar stability was based. In the post-Cold War period, scholars reflected over whether the end of ideological (capitalism/democracy vs. communism/single party authoritarianism) conflict presaged the end of history or inaugurated a clash of civilizations, with some questioning the salience of the concept of polarity and the viability of the state system in the face of rising subnational and transnational pressures.
Berenike Prem and Elke Krahmann
While early private military and security companies (PMSCs) were likened to mercenaries, today most scholars agree that PMSCs constitute a new phenomenon. They are organized as legitimate corporate entities, have a distinct legal status, and provide a wide range of military and security services. This definition reflects the evolution of the PMSC industry, which has moved beyond combat services to supply everything from transport, logistics, and maintenance to military and police training, demining, intelligence, risk analysis, armed and unarmed protective services, anti-piracy measures, border protection, and drone operations. Not only have PMSC services diversified, but so has their client base. In addition to industrialized and failed states, transnational corporations, international organizations, and even NGOs increasingly make use of PMSCs. There are several explanations for the growing recourse to these companies. Functional explanations see the employment of PMSCs as a rational response to the glaring gap between demand and supply in the market for force. Ideational and constructivist approaches, by contrast, impute national differences in the outsourcing of military and security services to dominant beliefs and norms about the appropriate relationship between the state and the market. The consequences of using PMSCs, including the accountability, effectiveness, and state control of PMSCs, issues of gender and racial equality, and theoretical implications for the location of political authority and the public good character of security are key issues. So is the question of suitable forms of regulation for the industry, including national and international laws, informal industry self-regulations, and hybrid regulatory approaches such as multi-stakeholder initiatives and standard setting schemes.