Unipolarity, bipolarity and multipolarity. These categories provide rival conceptions of where power lies, and suggest what implications these may have for global peace and security. Realists and liberals disagree about which of these systems is more likely to prevent conflict.


 The way in which power is distributed in the international system, into unipolarity, bipolarity and multipolarity.

 A single pole of power, meaning one state dominates all others. To be hegemonic, a state must therefore possess ultimate power in all its capabilities and be able to engage in unilateral action anywhere in the world at any time.

Two competing poles of power. This is best characterised by the superpower rivalry between the US and Soviet Union during the Cold War. For true bipolarity, the two powers are evenly matched and there is a clear balance of power.

Multiple poles of power, in which several states compete with each other. They may have different strengths and weaknesses in terms of their power, but each wields relatively equal influence on the international stage.

Consideration of changing nature of world order since 2000 

Bipolarity refers to an international system which revolves around two poles (major power blocs). The term is most commonly associated with the Cold War, restricting its use to the dynamics of East–West rivalry during the ‘superpower era’. For a system to be genuinely bipolar a rough equality must occur between the two pre-eminent powers or power blocs, certainly in terms of their military capacity. Neorealists have argued that this equilibrium implies that bipolar systems are stable and relatively peaceful, being biased in favour of a balance of power. Liberals, however, have associated bipolarity with tension and insecurity, resulting from their tendency to breed hegemonic ambition and prioritize military power. 

Was the Cold War system a stable system?


■Realists mostly hold this view. The balance of power between the Soviet Union and the USA created a stable equilibrium, which meant that neither side would gain from waging all-out war against the other.

■ In his 1987 book The Long Peace, key realist proponent John Lewis Gaddis argued that the Cold War was a time of relative stability because although there were lesser conflicts, there was no direct conflict between the two main powers. Conflicts between other powers were also ultimately less likely because all states revolved around the two main ideologies (communism and capitalism).

■ The principle of mutually assured destruction (MAD) meant that neither power would launch a military or nuclear attack on the other. Both sides therefore had an incentive to avoid war.


■ Liberals generally hold this view, since they see the Cold War as a dangerous and turbulent time.

■ Although avoiding direct conflict throughout the entire period, both sides tested the resolve of the other through global proxy wars.

■ MAD was far from stable — it nearly ended in nuclear war during the Cuban Missile Crisis in 1962. According to Robert S. McNamara, who was John F. Kennedy’s defense secretary at the time, ‘We lucked out. It was luck that saved us.’

■ There were no stabilising checks and balances on the superpowers, given the UN’s ineffectiveness at this time.

Liberals and realists have very different opinions on whether or not this system of Cold War bipolarity created global stability. According to realists such as Kenneth Waltz, the Cold War promoted peace, since the existence of two evenly balanced powers meant that neither side was capable of eliminating the other. As a result, both sides appreciated the limits of what they could achieve and so a balance of power was established, which it was not in the interests of either side to try to undermine. If one side had risked war, the results for both would have been catastrophic.

The Cold War period was described as ‘bipolar’ since power was divided largely between the US and its allies on the one hand, and the USSR and its allies on the other. The structure of bipolarity, together with the deterrent effect of nuclear weapons possessed by both sides, is often said to have produced the ‘long peace’ of the Cold War period in which major interstate warfare was threatened but did not actually occur. There is no agreement, however, as to whether a unipolar, bipolar, or multipolar system promotes greater security.

This therefore created an equilibrium that neither side was prepared to break, since by destabilising the equilibrium it would have created conflict due to the threat of mutually assured destruction (MAD). Indeed, some political commentators have even argued that Cold War bipolarity actually encouraged understanding and conflict resolution, since both sides understood that often the best way of advancing their own interests was by working with the other. For example, following the death of Joseph Stalin in 1953, diplomatic relations briefly improved between the secretary-general of the Soviet Union, Nikita Khrushchev, and President Dwight Eisenhower. In 1959 in Moscow, for example, Khrushchev and Vice-President Richard Nixon engaged in an informal and jocular exchange about the relative merits of their two world views. Soon after, Khrushchev visited Eisenhower in Washington, DC to further try to develop trust between the two sides.

During the 1970s, President Richard Nixon and Secretary-General Leonid Brezhnev established a period of détente between the USA and the Soviet Union. One consequence of this was the Strategic Arms Limitations Treaty (1972), which slowed the arms build-up between the two powers. The 1975, Helsinki Accords, which were signed between Nixon’s successor, Gerald Ford, and Leonid Brezhnev, provide the best example of the sort of cooperation that can be achieved in a bipolar world. Not only did Helsinki involve each side, guaranteeing the borders of the other, it even included commitments to increase economic, technical and cultural relations between them. However, according to liberals, bipolarity is destabilising and dangerous. This is because both sides will continually be advancing their military, diplomatic and economic interests at the expense of the other, so creating fear, suspicion and latent hostility. It, therefore, does not provide the conditions for a lasting or meaningful peace. According to the Ancient Greek historian Thucydides, it was actually the inherent dangers of bipolarity that led to the Peloponnesian War between Athens and Sparta (431 bce–404 bce), since ‘what made the war inevitable was the growth of Athenian power and the fear which this caused Sparta’. Therefore, liberals claim that the Cold War was much more defined by very long periods of mutual distrust and antagonism, as illustrated by US paranoia about a ‘missile gap’ in the 1950s or the ease with which the Cuban Missile

Crisis could have provoked nuclear war as the Soviet Union sought to pull ahead in the arms race by placing nuclear missiles in Cuba. The early 1980s were also profoundly unstable as President Ronald Reagan dramatically increased spending on nuclear weapons in order to prove US superiority over the Soviet Union. In 1983, as we have seen, the Soviet Union shot down a South Korean airliner, which could have provoked a military response from the USA. In the same year, the Soviets came close to a military strike on the West when they made the mistake of thinking that the NATO military exercise Operation Able Archer was the real thing. The way in which both events came very close to provoking direct military confrontation was, of course, due to the profound distrust between the two adversaries. Indeed, according to Robert S. McNamara, who served as US defense secretary from 1961 to 1968, ‘Cold War: hell it was a hot war!’

During the Cold War, both sides also tried to extend their global influence at the expense of the other through ‘hot wars’. In the Vietnam War (c.1963–75), the Soviet Union and the USA were not in direct combat, but they took opposing sides and backed these sides (North Vietnam and South Vietnam respectively) to win. Each saw a victory as furthering their position in the superpower rivalry. Alternatively, peripheral wars were fought between one superpower and another country (but the superpower’s opposition would be allied to their superpower rival). For example, during the Korean War (1950–53) the USA fought alongside South Korea to restrict Communist advance in the Korean peninsula.

End of Cold War bipolarity 

Although there is considerable debate about the nature of twenty-first century world order, there is considerable agreement about the shape of world order during the Cold War period. Its most prominent feature was that two major power blocs confronted one another, a US-dominated West and a Soviet-dominated East. In the aftermath of the defeat of Germany, Japan and Italy in WWII and with the UK weakened by war and suffering from long-term relative economic decline, the USA and the Soviet Union emerged as ‘superpowers’, powers greater than traditional ‘great powers’. Their status was characterized by their preponderant military power (particularly in terms of their nuclear arsenals) and their span of ideological leadership. Cold War bipolarity was consolidated by the formation of rival military alliances, NATO in 1949 and the Warsaw Pact in 1955, and it was reflected in the division of Europe, symbolized by the Berlin Wall erected in 1961.

 The bipolar model of the Cold War, however, became increasingly less accurate from the 1960s onwards. This was due, first, to the growing fragmentation of the communist world (notably deepening enmity between Moscow and Beijing, the Chinese Revolution having occurred in 1949) and secondly to the resurgence of Japan and Germany as economic superpowers. One of the consequences of this emerging multipolarity was détente between East and West. This was reflected in President Nixon’s historic visit to China in 1972 and the Strategic Arms Limitation talks between 1967 and 1979 that produced the SALT I and SALT II Agreements. 

What were the implications for the international system of Cold War bipolarity? 

For neorealists in particular, bipolarity is biased in favour of stability and order. This occurs for a number of reasons.

 First, and most importantly, bipolar systems tend towards a balance of power. During the Cold War, the approximate, if dynamic, military equality between the USA and the Soviet Union inclined both of them towards a strategy of deterrence. Once a condition of Mutually Assured Destruction (MAD) was achieved, the two superpowers effectively cancelled each other out, albeit through a ‘balance of terror’. 

Second, stability of this period was guaranteed by the fact that there were but two key actors. Fewer great powers reduced the possibilities of great-power war, but also, crucially, reduced the chances of miscalculation, making it easier to operate an effective system of deterrence. 

Third, power relationships in the Cold War system were more stable because each bloc was forced to rely on inner (economic and military) resources, external (alliances with other states or blocs) means of expanding power not being available. Once the division of Europe was developed, in effect, into the division of the world, shifting alliances that may have destabilized the balance of power were largely ruled out. Bipolarity therefore led to the ‘long peace’ between 1945 and 1990, in particular bringing peace to a Europe that had been the crucible of world war twice before in the twentieth century. 

However, not all theorists had such a positive view of Cold War bipolarity. One criticism of the bipolar system was that it strengthened imperialist tendencies in both the USA and the USSR as, discouraged from direct confrontation with each other, each sought to extend or consolidate its control over its sphere of influence. In the capitalist West, this led to neocolonialism, US political interference in Latin America and the Vietnam War, whereas in the communist East it resulted in the Warsaw Pact invasion of Hungary (1956) and the Soviet invasions of Czechoslovakia (1968) and Afghanistan (1979). 

A further criticism of bipolarity was that superpower rivalry and a strategy of nuclear deterrents produced conditions of ongoing tension that always threatened to make the Cold War ‘hot’. In other words, the Cold War may have remained ‘cold’ more because of good fortune or the good sense of individual leaders, rather than through the structural dynamics of the system itself. Even though neorealism may be effective in highlighting some of the benefits of Cold War bipolarity, it struggles to explain its collapse. The programme of accelerating reform, initiated by Mikhail Gorbachev from 1985 onwards, ended up with the Soviet Union relinquishing many of its core strategic achievements, notably its military and political domination over Eastern Europe, as well as, ultimately, over the non-Russian republics of the Soviet Union. 

On the other hand, the image of equilibrium within the Cold War bipolar system may always have been misleading. As will be discussed later, in many ways the USA became the hegemonic power in 1945, with the Soviet Union always as a challenger but never as an equal. 

This was reflected in the fact that while the Soviet Union was undoubtedly a military superpower it, arguably, never achieved the status of an economic superpower. Moreover, the imbalance between its military capacity and its level of economic development always made it vulnerable. This vulnerability was exploited by Ronald Regan’s ‘Second Cold War’ in the 1980s, when increased US military spending put massive pressure on the fragile and inefficient Soviet economy, providing the context for the Gorbachev reform process 

During Ronald Reagan’s presidency (1981–89) the USA achieved a commanding lead in the Cold War. The economic pressures of competing with the USA undermined the Soviet economy and under Secretary-General Mikhail Gorbachev, economic and political reforms were introduced. According to the nineteenth-century French historian and political theorist Alexis de Tocqueville, the most dangerous time for a dictatorship is when it begins to reform, since that reform is likely to be too slow to please its restive population. This was certainly the case with Gorbachev’s reforms.

As the momentum behind reform gathered pace, he gave more and more power to the constituent parts of the Soviet Union, the biggest of which, by far, was Russia led by Boris Yeltsin. When Communist hardliners tried to overthrow Gorbachev in 1991, it was Yeltsin who rallied the nationalist opposition, defeated the coup and then, by declaring Russia independent, led to the dismantling of the Soviet Union. The union was formally dissolved on 26 December 1991. The break-up of the Soviet Union established 15 new independent states. Russia was, of course, the biggest, but many of the others were extremely weak economically and left politically fragile from years of oppressive communism. They also faced struggle in terms of divided ethnic identities, particularly as state borders were being redefined.