Framework of unipolarity
Practical arrangements in different alliances vary enormously but the essential element in a meaningful alliance is a commitment for mutual support against external actor(s).
Unipolarity and alliance formation
The advent of unipolarity has had profound effects on the nature of contemporary alliances. A preponderance of power in the hands of a single state—in this case, the United States—had never before occurred in the modern era.
Academic discourse
The relevance of balance-of-power theory has been challenged in recent years by the emergence of unipolarity (e.g. Brooks and Wohlforth 2008; Levy 2004, Rhodes 2004). James Morrow (1991) has elaborated on the incentives and cast light on different trade-offs with respect to symmetrical and asymmetrical balancing regarding alliance formation. His analysis focuses on the difference between symmetric and asymmetric alliances and points out the differences between these two kinds of relationship.
Between the two positions of “balancing and non-balancing”, T. V. Paul has argued that states will be inclined to pursue soft balancing in the case of unipolarity. Paul argues that ‘hard’ balancing is excessively costly in the light of US strength. States will therefore seek to counter the US by means of softer measures and try to limit the US dominance (Paul 2004, Pape 2005, Hansen 2009).
Because the gross distribution of capabilities helps identify potential sources of threat and the potential allies that might be recruited, the condition of unipolarity inevitably shapes the alliance choices that are available to different states. A unipolar distribution of capabilities will also influence bargaining within contemporary alliances, based on the relative strength of different actors and the alliance options available to each.
The primary purpose of most alliances is to combine the members’ capabilities in a way that furthers their respective interests, especially their security goals. The present literature sees alliances primarily as a response to an external threat. Threats, in turn, are a function of power, proximity, specific offensive capabilities and aggressive intentions.
Unipole’s greater freedom
By definition, unipolarity means that the unipole has greater freedom of action than other major powers do. It does not have to worry about direct opposition from any country possessing roughly equal capabilities. Alliance ties in bipolarity are to large extent structurally determined whereas in unipolarity, structural imperatives are either absent or greatly diminished. With less need for a large alliance network, the unipole has greater leeway to opt for its preferences.
Thus, the US as the unipolar power, will be more inclined to align with states for which it feels a strong ideological affinity or with states that demonstrate a clear willingness to follow its lead.
On the other hand, unipolarity inevitably creates concerns about the imbalance of power in the unipole’s favor. This is an inevitable structural feature of unipolarity, because the unipole can act on its own and because its actions will have far-reaching effects.
Even if the unipole is not hostile and does not pose an existential threat to most other states, it may still take actions that inadvertently harm the interests of others. Thus, even the allies will be concerned about the concentration of power in the unipole’s hands.
Changing characteristics
The unipolarity situation creates greater obstacles to the formation of an effective balancing coalition. When one state is far stronger than the others, it takes a larger coalition to balance it, and assembling such a coalition entails larger transaction costs and more dilemmas of collective action. Moreover, if a balancing coalition begins to emerge, the unipole can try to thwart it by adopting a divide-and-reign strategy: punishing states that join the opposition while rewarding those that remain aloof or support the unipole instead.
The unipolarity fundamentally alters the tension between the twin dangers of abandonment and entrapment. Weaker states have to worry more about abandonment—because the unipole needs them less—and the unipole will be less likely to be dragged into conflict by reckless or adventuristic allies. For great powers, in short, the abandonment/entrapment dilemma will be most intense under multipolarity, somewhat diminished under bipolarity, and least worrisome under unipolarity.
Hansen (2009) postulates that the balancing does not prevail in the unipolarity but produces the free-riding / flocking dilemma because it creates the hard work dynamic. The hard work dynamic conceptualizes the additional need of the state to struggle for its security by its own means in the absence of a multiple-option bargaining position. The hard work dynamic produces incentives for other states to either flock around the superpower or to free-ride.
Flocking occurs when (some of the) other states follow the single superpower. Flocking thus reflects the superpower being able to provide the greatest amount of additional security against a threat (whether direct or indirect).
Free-riding is a classic strategy but two conditions render it particularly tempting in the case of unipolarity; first, the general stability of the system and lack of great power wars and tensions, and second, the strong international involvement of the superpower, which produces security whether or not the state in question participates.
In unipolarity, according to Hansen, balancing strategies are expected to come in different forms due to different incentives. The other states cannot balance the single superpower in conventional ways but they still have incentives to prevent the situation from turning into a monopoly of power. Apart from free-riding, they may pursue soft and issue-specific strategies.
According to Walt (2009), most alliances in unipolarity will reflect either an effort to align against the unipole or an attempt to accommodate it and exploit its power.
The responses, depicted in Figure 2, range from extreme opposition to the unipole to formal alignment with it.
Figure 2 (Walt 2009)