Unipolarity means, literally “having one pole.” In politics and international relations, it means that power is centered in one place. It contrasts with bipolarity and multipolarity.
In a bipolar system, two main centers of powers exist.
During the Cold War, this system existed. The USA was the center of one side (the NATO alliance), and the Soviet Union was the central power on the opposing side (the Warsaw Pact).
After the collapse of the USSR, there was no country that matched the population, economic and military power, and nuclear arsenal of the USA. Thus, the United States became the UN polar actor (sometimes called a global hegemony), in that it was able to dictate strong policies around the world.
The US, for example, could lead a war against Iraq in 1991, because the collapse of the Soviet bloc meant that American strength was almost unopposed. The US was also able to intervene in Bosnia and Kosovo, even against Russian objections, because Russian threats were no longer credible the US was too powerful to challenge. That is the essence of UN polarity.
As years passed, Russia began to regain strength, China became a major player on the world economic stage (and its military power has grown, as well), and the increased collaboration of European governments created the European Union.
Thus, it is becoming harder for a single country, even the USA, to “go it alone” on matters of global importance. Some political theorists say that we are now, or soon will be, in a multi polar system, where more than two centers of power exist, and they must share power and cooperate with each other to form alliances and achieve their goals.
The concept of polarity in the international system is used to describe the distribution of power capabilities across states. Polarity is a descriptive term that illustrates the structure of the system through a portrayal of the concentration of hard power capabilities in the system.
The three main variations in polarity are UN polarity, bipolarity and multipolarity. However, it is important to recognize that even within each type of polarity there exist variations.
For example, John Mearsheimer has distinguished between balanced multipolarity and unbalanced multipolarity, which depend on the degree to which power capabilities vary among multiple great powers.
Polarity is a system- level concept that relates to the distribution of power, real or perceived, in the international system. Unilateralism and multilateralism are choices about the policies that states adopt within a given international system.
Unipolarity implies neither the absence of all politics among great powers nor the absence of the power balancing among lesser powers nor certainly the resolution of all global problems. It does not mechanistically determine a specific strategy on the part of the major powers.
It simply creates incentive for strategies that diminish in not eliminate two major problems that bedeviled international systems of the past: struggles for global primacy and competitive balancing among the major powers.
The US follows a strategy of maintaining a preponderance of power globally and deep engagement in the security affairs of Europe, Asia and the Middle East.
It has adapted rather than abandoned the central institutions and practices it fostered during the bipolar era, expanded the North Atlantic Treaty Organization (NATO) to central Europe, strengthened its military alliance with Japan, and taken on a great many other less heralded new security commitments in areas formerly under the grasp of the Soviet Union.
While UN polarity captures the essence of the distribution of power in a system, it does not capture the amount of influence exerted on others in the system.
Even in a UN polar system, the dominant state can choose to demonstrate little or no desire to Control both the internal and external affairs of states around the global. In other words, UN polarity is a necessary, but not sufficient condition for the status of global hegemony.
For realists, the debate over the structure of international politics is primarily centered on two explanations of world order: balance of power theory and balance of threat theory. Both theories have different predictions and policy prescriptions for US behavior in the post- cold war would.
Within the realist debate about the emerging structure of international politics, several commentators have suggested new configurations of world power. Some commentators have cited the erosion of US primacy as evidence of a changing international system. For instance, Samuel Huntington proposed that changes in post-Cold War international politics reflects a uni-multipolar system with one superpower and several major powers.
It has been argued that the waning of ‘American hegemony’ has given rise to the regional power centers of Europe and East Asia. However, despite the devolution of US power globally, the shift towards multipolarity is several decades from now.
The extent to which post-Cold War international politics remains UN polar will depend on the cautious exercise of US preponderance and its ability to convince other states of its apparent ‘benign intent.
The durability of unipolarity has been particularly questioned by neo-realists. For neo-realists, unipolarity is the least stable of all structures because any great concentration of power threatens other states and causes them to take action to restore a balance.
Other commentators suggest that a large concentration of power works for peace, and they doubt that US preponderance is fragile and easily negated by the actions of other states. Despite this, many analysts argue that unipolarity is an ‘illusion’, a ‘movement’ that will not last long, or is already giving way to multipolarity.
Those who see the world as multipolar and embrace genuinely multilateral policies include Michael Lind, who has called for an effort to revive a concert of great powers, as well as David Calleo and Charles Kupchan, both of whom also embrace a form of multipolar multilateralism, albeit one that is highly Eurocentric.
Lind argues that the US should concentrate on working with the other major powers in the United Nations Security council (UNSC) and the G8, an approach that will spare the US the need to choose between a reflexive multilateralism that subordinates US interests to the rule of small and weak countries and an arrogant unilateralism that places the US at odds with the rest of the world.
Calleo and Kupchan see the European Union (EU) as evolving into a great power counterpart of the US, one that is neither weak nor necessarily a threat to US interests. Calleo sees a stronger EU as the natural partner of a chastened and more modest US in building a “cooperative multilateral system based on rules with an effective balance of power to sustain those rules,” while Kupchan heralds the “return of a world of multiple power centers” in which Europe is America’s only near-term major competitor.
The grand strategy of preserving unipolarity was enunciated in the Defense Planning Guide (DPG) of 1992. The paper stated that the US “must maintain the mechanisms for deterring potential competitors from even aspiring to a larger regional or global role.”
For Huntington, international primacy is “the ability of one actor to exercise major influence on the behavior of more actors with respect to more issues than any others government.” Kenneth Waltz argues that the ability of the US to exert international influence is determined by its different sources of power.
For Waltz, size of population and territory, resources endowment, economic capability, military strength, political stability and competence rank high as important sources of power.
The strategic direction of the 1992 DPG was driven by a desire to preserve US primacy. In addition to maintaining US primacy, the DPG envisioned the US seeking to prevent the rise of challenges by promoting international law, democracy and free-market economies.