Polarity (international relations)
The international system distributes power in ways that shape global history. One generally distinguishes three types of systems: unipolarity, bipolarity, and multipolarity for three or more centers of power. The type of system is completely dependent on the distribution of power and influence of states in a region or across the globe. This description captures the nature of the international system at any given period of time. Scholars examine how these distributions affect stability and conflict without assuming one structure is inherently superior.
The Cold War period was widely understood as one of bipolarity with the US and the USSR as the world's two superpowers from 1947 to 1991. Most Western and capitalist states fell under the influence of the US while most Communist states aligned with the USSR. Historic examples include ancient China's Chu and Jin during the years 636, 546 B.C. Rome and Persia maintained rivalry between 63 B.C. and 395 A.D. Great Britain and France competed from the end of the War of the Spanish Succession in 1701 through the Seven Years' War ending in 1763. These historical instances demonstrate how two dominant powers create spheres of influence and alliance systems around each pole.
Political scientists do not have an agreement on what kind of international politics polarity produces the most stable and peaceful system. Kenneth Waltz and John Mearsheimer argue that bipolarity tends to produce relatively high stability because two great powers engage in rapid mutual adjustment. In contrast, John Ikenberry and William Wohlforth argue for the stabilizing impact of unipolarity. Some scholars like Karl Deutsch and J. David Singer claimed multipolarity was the most stable structure. Bruce Bueno de Mesquita argued that the correlation between polarity of any kind and conflict is statistically weak and depends critically on systemic uncertainty and risk attitudes among individual actors.
Numerous thinkers predicted U.S. primacy in the 20th century onwards including William Gladstone and H. G. Wells in Anticipations published in 1900. The Cold War ended leading to unipolarity with the US as the world's sole superpower in the 1990s and 2000s. Liberal institutionalist John Ikenberry argues the United States purposely set up an international order after World War II that sustained U.S. primacy through strategic restraint. A unipolar state is not the same as an empire or a hegemon that can control the behavior of all other states. American hegemony is reluctant open and highly institutionalized according to Ikenberry's analysis.
Multipolarity is a distribution of power in which more than two states have similar amounts of power. Examples of wartime multipolarity include World War I, World War II, the Thirty Years War, and the Warring States period. Classical realist theorists like Hans Morgenthau hold that multipolar systems are more stable because great powers gain power through alliances without directly challenging others. Neorealists argue multipolar systems are particularly unstable due to greater complexity in managing alliance systems. Thomas Christensen and Jack Snyder suggest multipolarity tends towards instability from chain-ganging where allies get drawn into unwise wars provoked by partners.
The Correlates of War uses a systemic concentration of power formula developed by J. David Singer et al. in 1972 to calculate polarity. The expression represents the sum of the squares of the proportion of power possessed by all states in the great power system. The closer the resulting concentration is to zero the more evenly divided power is while results near one indicate concentrated power. A result between 0.4 and 0.5 usually indicates a unipolar system whereas 0.2 to 0.4 usually indicated bipolar or multipolar systems. Concentration can be plotted over time so fluctuations and trends in concentration become observable for researchers analyzing global power dynamics.
Common questions
What are the three types of international systems in polarity?
The three types of international systems are unipolarity, bipolarity, and multipolarity. These categories describe how power is distributed among states globally or within a region.
When did the Cold War period occur as an example of bipolarity?
The Cold War period occurred from 1947 to 1991 with the US and USSR acting as the two superpowers. Most Western capitalist states fell under US influence while Communist states aligned with the USSR during this time.
Who argued that bipolarity produces relatively high stability?
Kenneth Waltz and John Mearsheimer argue that bipolarity tends to produce relatively high stability because two great powers engage in rapid mutual adjustment. This view contrasts with scholars who support other forms of polarity for peace.
In which years did Rome and Persia maintain rivalry?
Rome and Persia maintained rivalry between 63 B.C. and 395 A.D. This historical instance demonstrates how two dominant powers create spheres of influence and alliance systems around each pole.
How does the Correlates of War formula calculate polarity concentration?
The Correlates of War uses a systemic concentration of power formula developed by J. David Singer et al. in 1972 to calculate polarity. The expression represents the sum of the squares of the proportion of power possessed by all states in the great power system.