Polarity (international relations)

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NATO and countries with which it is supposed to be at peace account for over 70% of global military expenditure,[2] with the United States alone accounting for 43% of global military expenditure[3] in 2009 and more than the next 17 combined in 2010[4] with NATO then taking about half of the global $1.6 trillion.[5]



  • Unipolarity is an interstate system and not an empire. Monteiro cites Robert Jervis of Columbia University to support his claim, who argues that “unipolarity implies the existence of many juridically equal non-states, something that an empire denies.”[6] Monteiro illustrates this point further through Daniel Nexon and Thomas Wright, who state that “in empires, inter-societal divide-and-rule practices replace interstate balance-of-power dynamics.”[7]
  • Unipolarity is anarchical. Anarchy results from the incomplete power preponderance of the unipole. Columbia University's Kenneth Waltz, whom Monteiro cites, argues that a great power cannot “exert a positive control everywhere in the world.”[8] Therefore, relatively weaker countries have the freedom to pursue policy preferences independent of the unipole. The power projection limitations of the unipole is a distinguishing characteristic between unipolar and hegemonic systems.
  • Unipolar systems possess only one great power and face no competition. If a competitor emerges, the international system is no longer unipolar. Kenneth Waltz maintains that the United States is the only “pole” to possess global interests.[8]

The post-Cold War international system is unipolar: The United States’ defense spending is “close to half of global military expenditures; a blue-water navy superior to all others combined; a chance at a splendid nuclear first strike over its erstwhile foe, Russia; a defense research and development budget that is 80 percent of the total defense expenditures of its most obvious future competitor, China; and unmatched global power-projection capabilities.”[1]

William Wohlforth, the Daniel Webster professor of government at Dartmouth College, believes unipolarity is peaceful because it “favors the absence of war among great powers and comparatively low levels of competition for prestige or security for two reasons: the leading state’s power advantage removes the problem of hegemonic rivalry from world politics, and it reduces the salience and stakes of balance of power politics among the major states."[9] This idea is based on hegemonic stability theory and balance of power theory. Hegemonic stability theory stipulates that “powerful states foster international orders that are stable until differential growth in power produces a dissatisfied state with the capability to challenge the dominant state for leadership. The clearer and larger the concentration of power in the leading state, the more peaceful the international order associated with it will be."[9] Balance of power theory stipulates that as long as the international system remains unipolar, balance of power theory creates peace. “Therefore one pole is best, and security competition among the great powers should be minimal.”[9] Unipolarity generates few incentives for security and prestige competition among great powers.

Nuno P. Monteiro argues that international relations theorists have long debated the durability of unipolarity (i.e. when it will end) but less on the relative peacefulness unipolarity brings among nations within an international system. Rather than comparing the relative peacefulness of unipolarity, multipolarity, and bipolarity, he identifies causal pathways to war that are endemic to a unipolar system. He does not question the impossibility of great power war in a unipolar world, which is a central tenet of William C. Wohlforth in his book World Out of Balance: International Relations and the Challenge of American Primacy. Instead he believes “unipolar systems provide incentives for two other types of war: those pitting the sole great power against a relatively weaker state and those exclusively involving weaker states.”[1] Monteiro’s hypothesis is influenced by the first two decades of the post-Cold War environment, one that is defined as unipolar and rife with wars. “The United States has been at war for thirteen of the twenty-two years since the end of the Cold War. Put another way, the first two decades of unipolarity, which make up less than 10 percent to U.S. history, account for more than 25 percent of the nation’s total time at war.”[1]

American primacy[edit]

The United States is the only country in the early 21st century that possesses the ability to project military power on a global scale, providing it full command of the global commons. With no viable challenger on the horizon in the short term, the current distribution of power overwhelmingly favors the United States, making the world order it set out to construct in 1945 more robust. The question that remains for international relations theorists is how long this “unipolar moment” will last. Sean M. Lynn-Jones, editor of International Security, provides a summary of arguments put forth by Kenneth Waltz, John Ikenberry, and Barry Posen.[10]

Kenneth Waltz[edit]

In “Structural Realism after the Cold War,” Kenneth Waltz defends realist theory against a cascade of criticism that emerged after the Cold War. He provides a realist analysis of the currently unipolar structure of world politics, arguing that realism is the best theoretical lens to understanding international politics and the future of U.S. primacy. Waltz also takes on the democratic peace theory, which holds that no two democracies will go to war with the other, as one that doesn’t present a proper challenge to realism. War is rooted in the anarchic structure, or a self-help environment, of the international system, Waltz argues. Simply changing the domestic political structure of countries will not eliminate war. Waltz notes, however, that “democracies seldom fight democracies.”[11] But democracies are more likely to initiate wars against non-democracies because the former believes the latter must become democratized so as make the democratic peace more robust. Thus, the spread of democracy can decrease the amount of war in the world in Waltz’s view. The second challenge to realist theory argues that economic interdependence promotes peace. Waltz believes this causal logic is backward: Peace can promote economic interdependence. Peace abounds when a political monopoly on force, or a favorable balance of power, prevents revisionist powers from altering the status quo. After all, strong economic interdependence did not prevent war in 1914. The third challenge that Waltz confronts is the rise of international institutions as primary actors in international politics. Waltz argues that the structure of power in the international system determines the role of institutions. NATO, for example, is often cited as an institution that has outlived its original mandate—preventing a Soviet onslaught of Western Europe. In Waltz’s view, NATO’s continued existence conveniently “illustrates how international institutions are created and maintained by stronger states (e.g., the United States) to serve their perceived and misperceived interests.”[11] Finally, Waltz turns to the question of international politics and provides a realist interpretation to the U.S. unipolar moment, which he believes is fleeting for two reasons. With no great power to check its adventurism, the United States will weaken itself by misusing its power internationally. “Wide latitude” of “policy choices” will allow the U.S. to act capriciously on the basis of “internal political pressure and national ambition.”[11] Second, even if the United States acts benevolently, states will still attempt to balance against it because the power asymmetry demands it: In a self-help system, states worry not about other states’ intentions as they do other states' capabilities. “Unbalanced power leaves weaker states feeling uneasy and gives them reason to strengthen their positions,” Waltz says.[11] He sees China as already beginning to counter U.S. power. In conclusion, the U.S. unipolar moment is fleeting and multipolarity is already materializing.

John Ikenberry[edit]

In “Institutions, Strategic Restraint, and Persistence of American Postwar Order,” John Ikenberry explains why other great powers decided not to balance against the United States after the Cold War ended. In his view, realist predictions of power balancing did not bear fruit because the United States engaged in strategic restraint after World War II, thereby convincing weaker states that it was more interested in cooperation rather than domination. U.S. strategic restraint allowed weaker countries to participate in the make-up of the post-war world order, which limited opportunities for the United States to exploit total power advantages. Ikenberry notes that while the United States could have unilaterally engaged in unfettered power projection, it decided instead to “lock in” its advantage by establishing an enduring institutional order, gave weaker countries a voice, reduced great power uncertainly, and mitigated the security dilemma. The liberal basis of U.S. hegemony—a transparent democratic political system—has made it easier for other countries to accept the post-war order, Ikenberry explains. “American hegemony is reluctant, open, and highly institutionalized—or in a word, liberal” and “short of large-scale war or a global economic crisis, the American hegemonic order appears to be immune to would-be hegemonic challengers.”[12]

Barry Posen[edit]

In “Command of the Commons: The Military Foundation of U.S. Hegemony,” Barry Posen focuses exclusively on U.S. military capabilities. A key to U.S. preeminence is “command of the commons—command of the sea, space, and air.” But command of the commons and the U.S. persistence in maintaining its near omnipresence raise important questions for U.S. strategy: “Even before the September 11 terrorist attacks, the foreign policy debate had narrowed to a dispute between primacy and selective engagement, between nationalist, unilateralist version of hegemony, and a liberal, multilateral version of hegemony.”[13] U.S. command of the commons, Posen argues, provides a strong case for selective engagement. Posen believes that the Bush Doctrine was problematic because it not only created unease among U.S. allies, but also caused “others to ally against the United States.”[13] Securing the commons through selective engagement is a superior strategy because it cost effective, secures U.S. interests, and makes the nearly omnipresent U.S. military tolerable because it provides security guarantees to other nations.

Examples of unipolarity[edit]

The most recent example of a unipolar world has been one dominated by the United States of America since 1991, in the aftermath of the collapse of the Soviet Union. Other states and empires in the past have dominated their known worlds in a unipolar fashion. Some examples are below. Note that most of the cases as well as the dates given are open to some debate.


Bipolarity is a distribution of power in which two states have the majority of economic, military, and cultural influence internationally or regionally. Often, spheres of influence would develop. For example, in the Cold War, most Western and capitalist states would fall under the influence of the USA, while most Communist states would fall under the influence of the USSR. After this, the two powers will normally maneuver for the support of the unclaimed areas.

Spheres of influence of the two Cold War superpowers (the US and the USSR) in 1959.
    The "First World": NATO members (dark blue) and their "Western" allies (light blue).
    The "Second World": Warsaw Pact signees (red) and their Socialist allies (pink).
    The "Third World": Neutral nations (grey) and Colonies (green).


Multi-state examples of bipolarity[edit]

The bipolar system can be said to extend to much larger systems, such as alliances or organizations, which would not be considered nation-states, but would still have power concentrated in two primary groups.

In both World Wars, much of the world, and especially Europe, the United States and Japan had been divided into two respective spheres – one case being the Axis and Allies of World War II (1939–1945) – and the division of power between the Central Powers and Allied powers during World War I (1914–1918). Neutral nations, however, may have caused what may be assessed as an example of tripolarity as well within both of the conflicts.

The NATO and Warsaw Pact groupings could also be considered to be bipolar if one does not include the Non-Aligned Movement.



Empires of the world in 1910.

Opinions on the stability of multipolarity differ. Classical realist theorists, such as Hans Morgenthau and E. H. Carr, hold that multipolar systems are more stable than bipolar systems, as great powers can gain power through alliances and petty wars that do not directly challenge other powers; in bipolar systems, classical realists argue, this is not possible. On the other hand, the neorealist focuses on security and inverts the formula: states in a multipolar system can focus their fears on any number of other powers and, misjudging the intentions of other states, unnecessarily compromise their security, while states in a bipolar system always focus their fears on one other power, meaning that at worst the powers will miscalculate the force required to counter threats and spend slightly too much on the operation. However, due to the complexity of mutually assured destruction scenarios, with nuclear weapons, multipolar systems may be more stable than bipolar systems even in the neorealist analysis. This system tends to have many shifting alliances until one of two things happens. Either a balance of power is struck, and neither side wants to attack the other, or one side will attack the other because it either fears the potential of the new alliance, or it feels that it can defeat the other side.

One of the major implications of an international system with any number of poles, including a multipolar system, is that international decisions will often be made for strategic reasons to maintain a balance of power rather than out of ideological or historical reasons.

The Eastern Mediterranean Hellenistic kingdoms of the 3rd century BCE, which grew out of Alexander the Great's empire, formed a good example of a multipolar political world. Macedonia (Antigonids), Syria (Seleucids), Egypt (Ptolemies) vied with one another and states such as Pergamon, Parthia and the La Tene Celts in shifting alliances for domination of the region. Combinations against the strongest state kept any one from establishing hegemony, but eventually left all weakened enough to be dominated by Rome from the mid-2nd century BCE.[14]

The 'Concert of Europe,' a period from after the Napoleonic Wars to the Crimean War, was an example of peaceful multipolarity (the great powers of Europe assembled regularly to discuss international and domestic issues). World War I, World War II, the Thirty Years War, the Warring States period, the Three Kingdoms period and the tripartite division between Song Dynasty/Liao Dynasty/Jin Dynasty/Yuan Dynasty are all examples of a wartime multipolarity.


Nonpolarity is an international system which has been postulated by Richard Haass, featuring numerous centers of power but no center dominating any other centre. Centers of power can be nation-states, corporations, non-governmental organizations, terrorist groups, and such. Power is found in many hands and many places.[15] It suffers from attempting to use liberal conceptions of power within a realist paradigm, diluting the meaning of 'polarity', and is not widely found in usual discussions of polarity.[16]


Though usually defined as the decentralization of power within a state, the term devolution, when applied to international relations, describes the process by which economically and militarily emerging states gain greater autonomy in regional affairs but do not achieve global power status. Against the theory that the world is moving from a unipolar order, dominated by the United States, to a multipolar world with various centers of power, Amitai Etzioni argues that, in the foreseeable future, the global redistribution of power is following a different pattern: "the change seems to be toward more regional autonomy, or increased devolution, and greater variety in the relationships between the United States and regional powers."[17] This alternative theory has policy implications as "the desire for more control among rising powers can be more readily accommodated than aspirations to challenge the United States as a global superpower."[18]

Measuring the power concentration[edit]

The Correlates of War uses a systemic concentration of power formula to calculate the polarity of a given great power system. The formula was developed by J. David Singer et al. in 1972.[19]

 \text{Concentration}_t = \sqrt{\frac{\sum_{i=1}^{N_t} (S_{it})^2 - \frac{1}{N_t}}{1 - \frac{1}{N_t}}}
  • Nt = the number of states in the great power system at time t
  • Sit = the proportion of power possessed by state i at time t (must be a decimal figure)
S = the proportion of power possessed
i = the state of which the proportion of control over the system's power is being measured
t = the time at which the concentration of resources (i.e. power) is being calculated
  • \sum_{i=1}^n (S_{it})^2 = the sum 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. The closer to 1, the more concentrated power is. There is a general but not strict correlation between concentration and polarity. It is rare to find a result over 0.5, but a result between 0.4 and 0.5 usually indicates a unipolar system, while a result between 0.2 and 0.4 usually indicated a bipolar or multipolar system. Concentration can be plotted over time, so that the fluctuations and trends in concentration can be observed.

See also[edit]


  • Thompson, William R. On Global War: Historical–Structural Approaches to World Politics. Columbia, SC: University of South Carolina Press, 1988, pp. 209–210.


  1. ^ a b c d e Monteiro, Nuno (Winter 2011–2012). "Polarity and Power: U.S. Hegemony and China's Challenge". International Security 36 (3): pp. 9–40, p. 9. doi:10.1162/ISEC_a_00064. Retrieved 13 November 2012. 
  2. ^ "The SIPRI Military Expenditure Database". Milexdata.sipri.org. Retrieved 2010-08-22. 
  3. ^ "The 15 countries with the highest military expenditure in 2009". Retrieved 2010-08-22. 
  4. ^ Economist .
  5. ^ World Bank
  6. ^ Jervis, Robert (January 2009). "Unipolarity: A Structural Perspective". World Politics 61 (1): pp.188–231, p. 190. doi:10.1353/wp.0.0031. Retrieved 13 November 2012. 
  7. ^ Nexon, Daniel and Thomas Wright (May 2007). "What's at Stake in the American Empire Debate". American Political Science Review 101 (2): pp. 253–271, p. 253. doi:10.1017/s0003055407070220. Retrieved 13 November 2012. 
  8. ^ a b Waltz, Kenneth (Summer 1964). "The Stability of a Bipolar World". Daedalus 93 (3): pp. 881–909, p. 887. JSTOR 20026863. 
  9. ^ a b c Wohlforth, William (Summer 1999). "The Stability of a Unipolar World". International Security 24 (1): pp. 5–41, p. 23. doi:10.1162/016228899560031. Retrieved 13 November 2012. 
  10. ^ Lynn-Jones, Sean (2008). Preface to 'Primacy and Its Discontents: American Power and International Stability. Cambridge, MA: The MIT Press. pp. xiii–xxviii. ISBN 9780262524551. 
  11. ^ a b c d Waltz, Kenneth (Summer 2000). "Structural Realism after the Cold War". International Security 25 (1): 5–41. doi:10.1162/016228800560372. Retrieved 13 December 2012. 
  12. ^ Ikenberry, G. John (Winter 1998–1999). "Institutions, Strategic Restraint, and the Persistence of American Postwar Order". International Security 23 (3): pp. 43–78. doi:10.1162/isec.23.3.43. JSTOR 2539338. 
  13. ^ a b Posen, Barry (Summer 2003). "Command of the Commons: The Military Foundation of U.S. Hegemony". International Security 28 (1): pp. 5–46. doi:10.1162/016228803322427965. Retrieved 13 December 2012. 
  14. ^ Hellenistic period
  15. ^ Haass, Richard N. (May–June 2008). "The Age of Nonpolarity". Council on Foreign Relations. Retrieved 2008-08-05. 
  16. ^ Grigsby, E. (2012). Analysing Politics. New York: Cengage (5ed). Pp. 255-259.
  17. ^ Etzioni, Amitai (Winter 2012). "The Devolution of American Power". The Fletcher Forum of World Affairs 37 (1): 13. 
  19. ^ Mansfield, Edward D. (March 1993). "Concentration, Polarity, and the Distribution of Power". International Studies Quarterly (Blackwell Publishing) 37 (1): 105–128. doi:10.2307/2600833. JSTOR 2600833. 

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