According to the theoretical model, we suggest the following hypotheses regarding dynamics and probable outcomes under unipolarity:

Durability of the unipolar system

A unipolar system is robust due to lack of great power competition but it is not necessarily durable as rivals may rise due to unit level developments or the single superpower may fail to deal with management challenges (overstretch or under-management)

Less and different balancing

Under unipolarity there are no great power rivals present to balance the single superpower (that is, symmetrical great power balancing). Instead, the other states may try to limit the influence of the superpower by means of soft or issue balancing or, most notably, by means of free-riding

Flocking and free-riding

Flocking and free-riding are the catch-words of unipolarity. If states faces a serious symmetrical security problem (individually or as a group of states) or for other specific reasons (regional) need a big ally, they have no other option but to flock around the superpower. On the other hand, if they aim to keep the superpower at bay or counter it because of own interests, their ’weapon’ is free-riding (in extreme case, they may try to go nuclear)

Warfare and interventions

Per definition, great power war is absent in a functioning unipolar system. Wars among the other states are limited because of the single option – that the one party may achieve the decisive superpower backing. On the other hand, superpower interventions is no longer prevented by a bipolar protagonist or encouraged by a multipolar great power game. Because of the lack of great power competition, unipolarity is generally characterized by low politics


Superpowers tend to manage challenges in world politics. A single superpower has a strong inclination to carry out management in order to maintain its privileged position. Compared to other polarities, the unipolar structural dynamics produce incentives to carry out even more management, because there are no symmetrically equal powers in the system to balance the efforts or to undertake parts of them. It is specific to unipolarity that the scope of the potential management has a global reach, and that the management is balanced only by the single superpower’s allocation of resources between domestic and external use. Furthermore, there will be an ongoing political conflict over how to distribute the costs. Among the other states, some will be inclined to free-ride while others are inclined to flock because of immediate gains or longer-term positional concerns

Benign or malevolent leadership

Even a single superpower cannot help to offend other states’ interests when carrying out management but the superpower might handle world affairs and its own resources in a way that produces less free-riding than it would otherwise be the case

Weak states, new states

Entrance on the unipolar market of states is facilitated by the lack of great power competition (no risk of the newcomer falling into the hands of the adversary/adversaries) in as much as secessionists are able to ally with the superpower. If not, the state in question risks disintegration and/or intervention


Terrorism cannot affect the unipolar structure but unipolarity encourages terrorism: the superpower is the centre of power and the focus of attention, and there is no other powerful ally that dissatisfied groups can turn to.

Disposition for terrorism is found mainly among those who loses out in the unipolar world order, currently characterized by its project for market and democracy

Nuclear weapons

In the nuclear age, numbers is less important. Instead, horizontal proliferation is a risk, particularly in the case of a state opposing the world order, and their aspirations create a huge management challenge. If the superpower achieves a first strike capability (possibly in terms of its own weapons combined with a defensive system) it may actually achieve an international monopoly of power and hence transform the international system into a hierarchically organized system.

Until other means are available, or the features of nuclear weapons are overcome, they will maintain their ability to compromise the structural dynamics and reduce the risk of war among nuclear powers

The world order

The concept of ‘world order’ is comparatively important in the case of unipolarity, and it is defined as the superpowers’ political projects divided by the number of superpowers. ‘Political project’ is understood as coordinated policies contributing to a general direction for leadership and setting the agenda. Furthermore, the direction is identified by means of the U.S. expressions of goals regarding the economy, politics and ideology, that is, a project for market and democracy.

In order to manage the whole world, the superpower’s project is inclined to be open and inclusive. This paves the way for imitation and voluntary socialization, but it also produces challenges from marginalized groups and states, and their competitive projects tend to be radical.


There are no alternative paths to socialization and imitation but only one reference for socialization and imitation. It pays to socialize to the world order and imitate the cornerstones of the U.S. political project: liberal democracy and the free market. A state can only escape the demands of the World Order if it is able to find innovative ways to compete 


As all hypotheses within the tradition of neorealism/structural realism, the above hypotheses indicates a probable room for outcomes: the theory is not deterministic but point to structurally inferred probabilities.

Furthermore, the hypotheses are very general: they tell us about the specifics of unipolarity compared to other polarities rather than, in the words of Kenneth Waltz, “why state X made a certain move last Tuesday” (Waltz 1979: 121).

Still there is a room for specifying the theory and the model for unipolarity, and contributions are most welcome

For arguments supporting the hypotheses, see B. Hansen: Unipolarity and World Politics, London and New York: Routledge, 2011. For neorealism/structural realism and its arguments, see Kenneth Waltz’s main work, Theory of International Politics, New York: Random House, 1979

Important results

The Way of the Vanquished

What if the current unipolar world order breaks down? How will the US respond to losing its precious position? Peter Toft has studied the reactions of previous fallen world powers in The Way of the Vanquished, and his insights provide intriguing answers that go beyond the ‘institutions matters’-debate.

The Way of the Vanquished: Fallen Great Powers and Responses to Collapse 1815-2004 explores why some of the major and great powers that experienced a sudden and steep relative decline in their international position responded differently to this similar fate.

Some of the fallen world powers e.g. France after 1815, Ottoman Turkey, and Russia after World War I strongly resisted decline and accepted high risks in order to rebuild their relative strength after their downfall while others, like the United Kingdom after World War II, preferred to settle relatively quietly to its new reduced global position.

In order to provide answers, the Way of the Vanquished explores the potential of the structural realist tradition in IR arguing that a high risk of exposure to political-military conflict (measured in terms of war-proneness of different polarities and a state’s geographic vulnerability) helped to shape the choice of post-fall strategy.

The study goes on to analyze this proposition against six cases of fallen great powers: France (1815), Germany, Soviet-Russia, and Ottoman Turkey (1918), the United Kingdom (1945), as well as Russia (1991).

♦ Toft, P. (2006) ‘The Way of the Vanquished: Fallen Great Powers and Responses to Collapse 1815-2004’, PhD Dissertation, Copenhagen: Faculty of Social Sciences, University of Copenhagen.

Adaptation and security strategies

In the meantime, important questions arise regarding the adaptation to the still unipolar world order. For an analysis of security strategies, see Security Strategies and American World Order – Lost Power:

This book analyses security strategies in the American world order, systematically comparing Russian, Middle Eastern and European policies.

The main finding is that the loss of relative power has decisive importance for the security strategies of states, but that particular strategies can only be explained when relative power is combined with ideology and the probability of military conflict.

Research on the unipolar world order has focused largely on the general dynamics of the system and the actions of the American unipole. By contrast, this book focuses on states that lost out relatively as a consequence of unipolarity, and seeks to explain how this loss has affected their security strategies. Thus, in essence, the book tells ‘the other side of the story’ about the contemporary world order.

In addition, it makes an important theoretical contribution by systematically coupling relative ideology and relative security with relative power and exploring their explanatory value.

♦ B. Hansen, P. Toft, and A. Wivel: Security Strategies and American World Order. London and New York: Routledge, 2009.

Ad Hoc Coalitions

‘Not Bound to Follow?’ engages in the examination of Ad Hoc Coalitions in the unipolar Era. The coalitions challenges the allied states with the dilemma of participating or not.

The dissertation asks why participation in post-Cold War US-led ad hoc coalitions varies and argues that the answer is found in the unipolar alliance security dilemma between fear of abandonment and fear of entrapment. The dilemma is influenced by primarily three variables: the unipole’s role in a conflict, the allies’ relationships to the unipole, and the level of severity of the dilemma.

The Ad Hoc Coalitions in Kuwait 1991, Somalia 1992, Haiti 1994, Kosovo 1999, Afghanistan 2001, and Iraq 2003 are examined.

In addition to providing results on alliance formation, the dissertation highlights variations in the relationship between the single superpower and its allies, and examines Ad Hoc coalitions as a central phenomenon in the unipolar Era. Furthermore, it provides valuable survey of coalition participation.

♦ Oest, K. J. N. (2009) Not Bound to Follow? Patterns of Allied Cooperation on the Formation of Ad Hoc Coalitions, Copenhagen: Department of Political Science, Ph.D. dissertation 2009/2