The U.S. Burden-Sharing Dilemma
A recent US president once complained that Washington’s allies do not pay their fair share for defense. “Free riders aggravate me,” he stated bitterly. “You have to pay your fair share.”
This president was not Donald Trump, who repeatedly made headlines by casting doubt on his willingness to protect US allies unless they made sufficient defense contributions. Rather, it was his predecessor, Barack Obama. Indeed, Obama’s Secretary of Defense went so far as to warn US partners that “there will be dwindling appetite and patience…to expend increasingly precious funds on behalf of nations that are apparently unwilling to devote the necessary resources…to be serious and capable partners in their own defense.”
Obama and Trump were hardly the first US leaders to solicit greater burden-sharing from US allies. In late 1953, President Eisenhower’s Secretary of State John Foster Dulles warned that unless Europe became more self-reliant, the United States would undertake “an agonizing reappraisal of basic United States policy” toward its commitment to the Continent. In much the same way, John F. Kennedy threatened to withdraw US troops from West Germany to secure compensation for the costs of stationing them in the country, declaring that “we cannot continue to pay for the military protection of Europe while the NATO states are not paying their fair share and [are] living off the ‘fat of the land.”’ Across numerous administrations, the need for allied burden-sharing has been a constant refrain in US foreign policy.
But there is striking variation in the success and, in fact, the incidence of US burden-sharing pressure. In some cases, burden-sharing pressure efforts succeed—Jimmy Carter, for instance, persuaded South Korea to increase its defense spending to 6 percent of gross national product when he leveraged the possibility of troop withdrawals. At other times, they fail—US pressure on the United Kingdom to retain its military presence in Asia during the 1960s amounted to little. And then there are those cases, perhaps most puzzling of all, where US officials have notably declined to seek greater allied contributions to the common defense. During the early 1970s, for example, the Nixon administration refrained from seeking a substantially greater Japanese military role despite the explicit ambition of the Nixon Doctrine to delegate more responsibility to allies to defend themselves. Similarly, US policymakers have repeatedly balked at the prospect of a united, independent European defense capability since the end of the Cold War.
This book attempts to understand such variation in burden-sharing within US alliances. It investigates why the United States sometimes puts pressure on its allies to bear more of the collective burden (and sometimes doesn’t) and when these burden-sharing pressures succeed (or don’t). To that end, it advances two central claims. First, US decisions to encourage allied burden-sharing at all are the product of calculations about both the benefits and the risks of greater allied self-reliance. Burden-sharing is useful insofar as it can purchase a similar amount of collective military power at lower US cost. But in some cases—particularly those in which allies have a realistic capability to go their own way—the United States actually prefers that its allies not assume more responsibility for their own defense, since doing so can reduce their dependence on US protection and, by extension, US influence. Second, if the United States elects to encourage allied burden-sharing, its success depends on whether allies fear that it will abandon them. The more credible its threat of abandonment, and the more allies depend on its protection, the more successful it will be.
Each claim challenges strands of conventional wisdom on burden-sharing. The first rethinks the assumption that larger allies disproportionately contribute to collective defense and are always encouraged to do so. I suggest that patrons like the United States actually have good reason not to encourage their largest allies to spend more on defense—namely, to prevent them from becoming too independent. The second claim confronts the notion that the United States’ ability to pressure allies into greater burden-sharing is inherently precluded by its disproportionately great power and vast network of overseas troop deployments. I show that the United States is in fact sometimes able to wield the threat of abandonment to encourage greater burden-sharing even among allies that host a substantial US troop presence. Thus, even though great powers like the United States may be constrained in their ability to solicit allied military contributions, they are far from helpless in doing so. The operative constraint on alliance burden-sharing is in some cases not the United States’ ability to secure it, but simply its willingness to seek it.
What We Know (and Don’t Know) about Burden-Sharing
Burden-sharing refers broadly to actions by which an alliance member contributes to the alliance’s capacity to carry out its objectives. These contributions can take a number of military or nonmilitary forms, such as deploying forces to active conflicts, hosting military bases, providing logistical support, or supplying aid. In this book, I focus on burden-sharing in the form of allies’ efforts to provide for their own defense and enhance their own military capabilities.
Burden-sharing is core to the functioning of alliances. By enabling states to pool resources, burden-sharing crucially ensures that alliances can achieve their collective goals, as they are unlikely to succeed in deterring and defeating adversaries unless their members possess sufficient capabilities. A lack of burden-sharing, or free-riding, can cause an alliance to fail to achieve its objectives if the patron is unwilling or unable to contribute enough by itself, and it can create discord in the alliance by generating resentment among members who feel taken advantage of. Burden-sharing additionally facilitates the self-preservation of great powers. Scholars have long argued that overinvesting in military power sows the seeds of great powers’ long-term decline by diverting resources from more productive investments and innovation. They offer evidence that even financing military spending through debt does not avoid painful fiscal trade-offs, as doing so can cause inflation and contribute to economic crises. These problems are especially challenging in asymmetric alliances between a more powerful great power patron and weaker partners, as the patron’s greater capacity to provide security for the alliance makes it tempting for weaker partners to seek a free ride. Securing allied burden-sharing thus allows a patron to ensure that its commitments do not exceed its resources, and that adversaries can be deterred at a sustainable cost.
The literature on burden-sharing, however, is generally pessimistic about its prospects in asymmetric alliances, largely portraying burden-sharing by smaller allies as an objective that great power patrons seek but have difficulty attaining. This pessimism partly has to do with the predominant view that alliances between great powers and weaker states feature an asymmetric exchange, wherein the former provides security for the alliance while the latter gives up some degree of foreign policy autonomy. From this perspective, the capacity for burden-sharing in asymmetric alliances is limited almost by definition; the great power already tacitly agrees to the costs of providing security in exchange for weaker states’ aligning their foreign policies with its own. Another cause for pessimism has to do with an understanding of alliances based on the logic of public goods, which emphasizes that larger alliance members tend to contribute disproportionately more to collective defense since it is their contributions that ultimately matter most. From this perspective, smaller allies rationally free-ride, and alliances with more members tend to feature more free-riding. Others likewise suggest that the global US military footprint and other assurances of US protection encourage allies to free-ride.
These studies thus leave gaps in our understanding of variation in burden-sharing. They cannot fully explain why France withdrew from NATO’s military command in 1966, despite being among NATO’s largest members; why Germany, since the end of the Cold War, has been among NATO’s lowest spenders on defense as a percentage of its gross domestic product (GDP); or why, by contrast, comparably smaller NATO members in the 2010s—notably Estonia, Latvia, Lithuania, and Poland—have punched above their weight. Moreover, they cannot fully explain why allies who hosted many US troops nevertheless spent a great deal on defense. Empirical research on the subject has produced mixed results and does not conclusively show that signals of alliance commitment negatively impact burden-sharing—some studies find that the presence of US troops has a negative effect on burden-sharing, but others find no such effect. While there are cases in which US protection almost certainly discouraged allies from making significant efforts toward self-defense—perhaps most famously Japan, whose constitution’s Article 9 imposes restrictions on its military, and Iceland, whose membership in NATO came with the assurance that it would not need to have a military—there are yet other cases in which allies hosting tens or hundreds of thousands of US troops still contributed a great deal to their own security, such as West Germany and South Korea.
Existing literature likewise has difficulty explaining why the United States has in other cases been reluctant to seek more burden-sharing from its partners. In addition to seeking just a modest military contribution from Japan, US officials only grudgingly accepted the need for West German rearmament during the early Cold War so that it could assist NATO in counterbalancing Soviet power in Central Europe. Similarly, US policymakers were lukewarm about European proposals for a more united European defense policy during the 1990s and 2000s, and even the Trump administration balked at proposals for a European defense fund.
What one is left with, then, are two puzzles. The first is that while in many cases the United States has been able to actively shape its partners’ military contributions—even in seemingly unlikely cases where allies hosted considerable numbers of US troops—other times it has failed to do so. The second is that in some cases the United States has actually preferred that its allies not maximize their military capabilities, even when doing so could have allowed it to conserve its own resources.
The Argument in Brief
These puzzles raise the following question: Under what conditions is the United States willing and able to encourage allied burden-sharing? The answer lies in what I call alliance control theory. Alliance control theory predicts that patrons like the United States will calibrate their burden-sharing pressure toward allies in consideration of three factors—an ally’s latent military potential, the external threat environment, and the patron’s resource constraints. It shows that a substantial amount of variation in asymmetric alliance burden-sharing is the result of bargaining between the patron and its weaker allies. Although alliances can discourage allies from investing in their own defense, a patron can mitigate this tendency by combining assurances of support with threats of abandonment. The extent to which the patron’s protection can be made conditional on allies’ burden-sharing efforts, in turn, depends on whether the patron is both willing to ask them to contribute more and able to credibly threaten to abandon them if they do not.
In deciding to seek allied contributions, a patron must balance competing priorities. On the one hand, burden-sharing allows a patron to secure military power for collective defense against shared adversaries without bearing the costs of doing so itself. For this reason, patrons can be expected to encourage allied burden-sharing when the alliance’s external threat environment is severe and when their own resources are constrained. On the other hand, asking allies to shoulder more responsibility for defending themselves reduces both the value of the alliance to them and their dependence on the patron’s protection. As such, patrons are likely to tailor their efforts at securing allied contributions not only to maximize cost savings, but also to minimize the risk of empowering allies to go their own way and exit the alliance. Patrons, in other words, are likely to take a “Goldilocks” approach to allied burden-sharing. While the smallest allies have little to contribute, and so pose the least risk of defection, larger allies, who have more to contribute, pose the greatest risks, since they have greater potential to fend for themselves outside of the alliance. Counterintuitively, then, it is not the allies who have the greatest potential to provide resources for collective defense that face the most pressure to contribute. Rather, it is moderately sized allies who are strong enough to make meaningful contributions, but not so strong that they can choose to leave the alliance given sufficient investments in defense.
If a patron does choose to seek greater burden-sharing, its success then depends on whether allies fear being abandoned by it. Two factors shape the effectiveness of patron burden-sharing pressure: whether a patron’s threat of abandonment is credible, and how badly allies need protection. A patron can more believably threaten to walk away from its alliances when it faces strains on its resources and pressure to retrench from domestic actors, which constrain its ability to maintain its commitments. Its threat of abandonment is also likely to carry more weight for allies who perceive a greater level of external threat and thus can less easily afford to lose the patron’s protection.
Patrons, in sum, face a burden-sharing dilemma—they must balance discouraging free-riding and encouraging allies to remain loyal to the alliance through a reduction of allies’ incentives and capabilities to act independently. Stated differently, patrons in asymmetric alliances must find a trade-off between control—their ability to influence allies’ preferences and persuade them to act in ways that align with their own—and cost-sharing—their ability to reduce the costs of military readiness for themselves and shift those costs onto their partners. Although patrons can never fully overcome this dilemma, they can nevertheless mitigate it by making their protection conditional on allied burden-sharing and manage it by exercising caution in their attempts to secure burden-sharing.
Contributions of the Book
This book advances the study of alliance politics on several fronts. It shows, first, that existing literature underestimates great power patrons’ ability to persuade their allies to shoulder a greater portion of the collective defense burden. I demonstrate that great power patrons are often surprisingly capable of encouraging allies to contribute more, even when those allies receive considerable signals of support such as troop deployments. In the case of the United States, there are three reasons for this capability. First, US assurances are not distributed randomly, and many of the same factors that drive the need for reassurance—such as when allies doubt their patron’s reliability or perceive a high level of external threat—also make them predisposed to burden-share. Indeed, the very fact that allies need to be reassured suggests that they may be vulnerable to their patron’s pressure. Second, even if the United States provides signals of support, allies may nevertheless fear that that support could be withheld at a later date. Finally, the United States can in some cases use the possibility of reduced protection to motivate allies, pairing threats to punish an ally if it does not comply with assurances that the ally will not be punished if it does.
At the same time, my findings show that existing literature overestimates the degree to which patrons actually want their allies to contribute more. Often, the challenge of alliance burden-sharing is not a question of whether a patron can extract burden-sharing concessions from its allies, but of whether it is willing to tolerate the risks of doing so. The conventional wisdom on alliance burden-sharing, based on the logic of collective goods, suggests that larger partners in an alliance inevitably pay a disproportionate share of the alliance’s defense burden. Yet, when one considers burden-sharing in the broader context of the alliance and as an outcome of alliance bargaining, a central challenge for the patron becomes evident: allies who can contribute more can also do more for themselves and go their own way, pursuing policies that the patron may oppose and ultimately weakening the alliance. In other words, an ally’s capacity for self-reliance poses the risk of alliance abandonment—a possibility underplayed in existing literature, which tends to view an ally’s ability to find other partners as the primary cause of alliance abandonment, and which thus tends to underestimate the risk of alliance exit in bipolar and especially unipolar systems. Thus, if a patron is deliberately seeking to suppress its larger allies’ military capabilities for the purposes of maintaining influence over them, then the notion that larger allies must always or should always be encouraged to contribute disproportionately more of their resources toward the alliance’s common defense does not hold. In the final analysis, burden-sharing is not an unalloyed good, since it may result in diminishing returns for the collective good. Inequitable burden-sharing in US alliances should therefore not be seen as a predetermined result of collective goods logic that the United States perpetually resists, but rather as a conscious choice.
This book also bears broader implications for understanding alliance management while pointing to the limits of alliance treaties as commitment devices. Based on the assumption that the presence of a formal alliance treaty is one of the strongest assurances of support and indicators of friendly relations among states, the literature on alliances has long focused on understanding the causes and consequences of alliance formation. It has also emphasized how alliance treaty design—for example, whether a treaty imposes strict conditions on supports or limits on behavior, is bilateral or multilateral, and is vague or precise—enables allies to lock in their leverage over partners. But the formation of an alliance is only the starting point; a great deal of bargaining takes place after an alliance treaty is signed. Moreover, a treaty’s ability to actually constrain partners and lock in bargaining leverage is limited, no matter how foolproof its initial design, since partners’ interests, capabilities, and intentions, along with the external environment, can change in ways that make the alliance less useful or shift bargaining power among members. While this book does not discount the importance of studying alliance formation or alliance treaty design, it does show, through the lens of burden-sharing, that what happens after alliances are formed between great power patrons and their weaker protégés is equally important. And by paying more attention to burden-sharing rather than treaty design, the book demonstrates that patrons are able to maintain their bargaining leverage over the long term by willingly accepting or even encouraging a degree of free-riding.
Finally, this book contributes to our understanding of alliances as tools of restraint and control. Scholars have long argued that alliances can restrain allies from launching offensive wars—both against each other, by fostering transparency and building trust, and against third parties, by allowing partners to mediate and use the threat of withholding support to dissuade adventurous allies. But an understudied mechanism by which alliances can restrain and control partners is by reducing their incentives for independent military arming or engaging in security competition with their neighbors, thus ameliorating local security dilemmas that could otherwise foster conflict. This book explores this mechanism precisely by identifying the conditions under which great power patrons are more likely to seek a way to limit their allies’ military power.
The next chapter of this book elaborates on alliance control theory, explaining the conditions under which the United States is willing and able to persuade its allies to increase their burden-sharing contributions. The chapter concludes with a discussion of alternative explanations and the book’s methodology. The next four chapters present case studies of the United States applying burden-sharing pressure on West Germany, South Korea, and Japan during the 1960s and 1970s, and on Iceland during the 1950s. These chapters draw on declassified government documents and secondary historical texts. The book then concludes with a summary of the findings as well as a discussion of policy implications and avenues for future research.
This article is an excerpt from The Burden-Sharing Dilemma: Coercive Diplomacy in US Alliance Politics (Cornell University Press, 2023, pp. 1-6, 9-11) by Brian D. Blankenship, published by Cornell University Press. Copyright (c) 2023 by Brian D. Blankenship. Reprinted by permission of the publisher.
Brian Blankenship is an Assistant Professor in the Department of Political Science at the University of Miami. His research and teaching interests are in the areas of international relations, international security, and international cooperation, with a focus on U.S. foreign policy and the politics of military alliances.
Image: White House Flickr.