Abstract
I introduce this issue's symposium on the Russo-Ukrainian War by giving a brief overview of the bargaining framework, which asks why states sometimes use war to resolve disputes despite common knowledge that fighting is wasteful. I describe two types of mechanism—costly war and costly peace—and briefly discuss each symposium contribution in relation to its proposed mechanism(s). I also discuss the advantages of the bargaining framework for identifying and ruling out potential causal mechanisms in historical cases and close with some suggestions for continued work in the modeling dialogue between theory and evidence in the study of war.
Russia's full-scale invasion of Ukraine in 2022 capped off months of international tensions, during which time Russian President Vladimir Putin publicly dismissed the notion of an independent Ukraine, demanded promises of Ukrainian neutrality as well as a reduction in NATO membership, and positioned his military for war, all while Russian spokespeople denied an intent to invade. When tanks finally rolled across the Russian and Belarusian borders and missiles fell on Ukrainian cities, to say nothing of when Ukrainian resistance threw the Russians back from many of their early gains, victims and observers alike were puzzled. Why did Russia embark on a costly, shambolic, and (thus far) ineffectual invasion of Ukraine when it had presumably scuppered the prospect of NATO membership by annexing Crimea and fomenting rebellion in the Donbas eight years earlier? Political speech can be an unreliable guide to explaining why war breaks out, especially when decision-makers compete for the support of domestic audiences and the sympathy of foreign ones. That has not stopped some commenters, even political scientists, from taking belligerents’ words at face value or from conceding the moral terms on which belligerents assign “fault” in war. This symposium, in contrast, takes a measured, theoretically grounded approach, one committed to simple “accounting standards” (Powell, 1999: 30–31) for logical coherence, to grappling with why Russia and Ukraine are now at war owing to the former's invasion of the latter, with many thousands dead and, as of this writing, no end in sight.
Social-scientific explanation is an exercise in identifying and ruling out putative causal mechanisms (Ashworth et al., 2021; Gailmard, 2021; Slough, 2023), which requires not just a set of observed facts but also valid arguments whose premises imply those facts (Wagner, 2007: chap. 1). When it comes to current history, like Russia's invasion of Ukraine, whose documentary record is still being written and about which key decision-makers have incentives to lie, a well-specified theory of war is essential for making guesses about the relevant causal mechanisms. To wit, the contributions to this symposium apply the bargaining framework, which collects several models that explore the implications of a key observation: countries contending over scarce goods can, and typically do, strike bargains that save the costs of war (Fearon, 1995: 383–390). So why do they sometimes choose war instead? With shared assumptions about actors, issues, and preferences, the bargaining framework explains the initiation (Benson and Smith, 2023; Powell, 2006), termination (Filson and Werner, 2002; Slantchev, 2003), and expansion (Fang et al., 2014; Wagner, 2004) of war, as well as the duration of peace once war ends (Phillips and Wolford, 2021; Werner and Yuen, 2005). Bargaining models (a) make clear statements about who does what and why on the path to war, (b) outline the observable conditions under which mechanisms are expected to matter, and (c) generate multiple observable implications that can help distinguish candidate explanations from one another. All of these strengths are on display in this symposium, which looks for the causes of the Russo-Ukrainian War in commitment problems owing to shifting power (Smith, 2024), information problems owing to incentives to bluff (İdrisoğlu and Spaniel, 2024), and domestic problems that may be most effectively solved through international war (de Vogel and Sun, 2024). In this introduction, I review the bargaining framework and situate each contribution within it, then close with a discussion of how the Russo-Ukrainian War can shape the modeling dialogue (Myerson, 1992; Powell, 1999: 24–27) between theory and evidence in the study of war.
The bargaining framework
This symposium applies what is variously called the bargaining “model” (Reiter, 2003), “approach” (Tarar, 2006), “theory” (Lake, 2010/11, Powell, 2002), or presently, “framework” to understand why leaders take their countries to war. However we modify “bargaining,” models in this tradition address a common puzzle (see Fearon, 1995: 383–390): fighting destroys more value than negotiating, so why do leaders sometimes choose the costlier means of resolving disputes? As Wagner (2007: chap. 4) has it, the point of fighting is to produce agreement on a new distribution of benefits, yet those same agreements can also be reached—and typically are!—without fighting. This is the inefficiency puzzle of war: everyone knows fighting is wasteful, so why are some agreements preceded by war?
Political scientists have identified two types of solution to the inefficiency puzzle, one in which countries go to war despite knowing that they will regret its waste and another in which they fight because war, its waste notwithstanding, generates benefits that peace cannot. As such, I will refer, respectively, to “costly war” and “costly peace” mechanisms (on the latter, see Coe, 2011). Costly war mechanisms explain fighting with respect to the strategic environment—i.e. structural obstacles to locating mutually acceptable bargains—while costly peace mechanisms focus on players’ preferences—i.e. why they might attach net benefits to war itself as a kind of consumption good (Fearon, 1995: 379, fn. 1), rendering negotiation irrelevant. Costly war mechanisms entail ex post regret, because belligerents can ask after the fact why they could not have reached the same distributive outcome without fighting. In contrast, costly peace mechanisms do not produce regret, because a costly war achieves something that a negotiated settlement cannot. Figures 1 and 2 highlight these essential differences between each type of explanation.
The ex post bargaining range when war is costly.
The absence of an ex post bargaining range when peace is costly.
Costly war
Suppose that states A and B negotiate over a continuously divisible bundle of all issues at stake between them (here, the “pie”), represented by a unit interval along which A prefers outcomes closer to 1 and B prefers outcomes closer to 0. Payoffs are linear in shares of the pie, ensuring that players are risk-neutral.
1
A peaceful settlement allocates x to A and
For players to accept a settlement, A requires
Why might states fight a war they know they will eventually regret? Costly war accounts identify two bargaining frictions—commitment problems and information problems—that can stand in the way of an efficient settlement. 3 When states face a commitment problem, agreements in the bargaining range may not be enforceable, because a rising state's chances of winning a war will increase tomorrow if the declining state does not attack today. Commitment problems cause war when (a) the rising side is either unwilling or unable to limit a favorable shift in relative power (see, e.g. Debs and Monteiro, 2014) and (b) it cannot commit not to use that increased power once realized. A declining side thus attacks preventively to arrest, slow, or end the adverse shift in power, paying an upfront cost rather than suffering future relative weakness. The standard result, owing to Powell (2006), is that a sufficiently “large” and “rapid” shift in power can cause war, producing a settlement based on the present distribution of power. Figure 1 shows that belligerents can agree ex post that they would have been better off agreeing to those terms without fighting, but of course the rising side would have been unwilling to abide by them had it been allowed to rise peacefully—hence the costly war to impose terms that could have been had in principle but not in practice.
Smith (2024) uses the logic of commitment problems to shed light on Moscow's decision to invade by tracing the decline of its ability to dictate terms to Kyiv. As Ukraine's politics shifted ever Westward, so did its prospective ability to resist Russian political influence, undermining the latter's goal of bringing Ukraine back under its imperial sway. With Ukraine unable to commit to neutralization and Russia, especially after 2014, clearly bent on bringing the most politically and economically important part of its former empire to heel, Russia invaded in hopes of preventing deeper Ukrainian integration with Europe. Smith also subverts traditional rising/revisionist and declining/status quo equivalencies (Gilpin, 1981; Monteiro and Debs, 2020) by showing that a shift in purely defensive power, like prospective Ukrainian admission to NATO, can see a revisionist state initiate a war, fearing a loss of future revisionist leverage. To the extent that possible NATO expansion caused Russia to invade Ukraine—i.e. that the war was the West's “fault” (Mearsheimer, 2022)—it was because ensuring Ukraine's political independence would have foreclosed future Russian encroachment on the same, not because it represented an existential threat to Russia.
In the second costly war account, players disagree over the boundaries of the bargaining range, incentivizing them to tolerate a risk of war for the chance of securing bigger concessions. Information problems arise when disputants have (a) private knowledge over the attractiveness of war—say, capabilities or resolve—and (b) incentives to misrepresent that knowledge. For example, governments typically know their own publics’ willingness to bear the costs of war better than their opponents, and governments believed to have the support of a resolute public will get better offers in crisis bargaining. This encourages governments to describe their publics as resolute even if they are not, and such incentives to lie create incentives to disbelieve (Fearon, 1995, 390–401). When a disputant with private information cannot credibly convey what terms it prefers in lieu of war, its opponent faces a “risk–return tradeoff” (Powell, 1999, 83): the more it demands, the better off it is at peace, but the more likely it is that those demands will be rejected by a disputant more capable or resolute than expected. Uninformed states make demands that entail a risk of war when they are sufficiently optimistic that their opponent either will not fight or will not win, and those demands are rejected when their opponents truly are willing to fight or likely to win. Fighting reveals the previously uncertain boundaries of the bargaining range, and states in Figure 1 can see they would have both been better off striking a bargain that reflects that just-revealed information. Yet lacking some means of credibly revealing it, one side made demands that risked rejection in hopes of securing better terms. 4
Where many applications of information problems take uncertainty as given and ask why states cannot find means of credible communication (e.g. Schultz, 1998; Weeks, 2008), İdrisoğlu and Spaniel (2024) focus on how states can develop sets of beliefs that make war possible in the first place. They trace the domestic political origins of Russia's overly optimistic initial beliefs that it could secure a quick victory through years of military corruption, institutional decay, and Putin's personal isolation, then show that Ukraine also had an optimistic but more accurate picture of its military prospects but no way to credibly convey that to the Kremlin. Russia therefore made demands commensurate with its belief that Ukraine would offer little resistance, and Ukraine resisted, leading to a military outcome wildly at variance with Russia's initial expectations. The authors also strengthen their case by drawing out an additional implication: given Russia's optimistic beliefs over its military prospects, meeting the minimum demands of a Ukraine that believed it could resist was too onerous, which (a) made war all the more attractive and (b) accounts for the substantial difference between the terms on offer and Russia's military performance in the war.
Costly peace
Costly war models treat fighting as instrumental, but the costly peace models described in Figure 2 focus on what war is good for. Returning to our example of states A and B, now suppose that war also generates a net benefit
In the final contribution, de Vogel and Sun (2024) analyze the Russo-Ukrainian War with a class of costly peace models rooted in domestic politics, showing first that institutional constraints as traditionally understood, especially those that bind more tightly in democracies (Bueno de Mesquita et al., 1999; Hyde and Saunders, 2020), did not stand in the way of a personalist regime's desire for war (Weeks, 2012). Next, they present evidence that the opportunity to reward supporters more cheaply during wartime than peacetime (Davis, 2023), e.g. securing and distributing spoils of conquest rather than engaging in costly redistribution at home, made invasion attractive. They also show that war might have also created unique opportunities to change the course of Ukrainian politics—i.e. war could install a friendly regime, but extracting similarly harsh concessions might have only encouraged a backlash—offering yet another example of war achieving things that negotiated settlements cannot. Intriguingly, this represents a potential second mechanism, in addition to the commitment problem, linking Ukraine's Westward turn to the 2022 invasion. In Figure 2's terms, remaining at peace with Ukraine may have posed problems that only war could solve, or foregoing war may have left certain domestic benefits on the table. That war solves a domestic problem also indicates that how it ends will be less tied to military fortunes than war caused by information or commitment problems (see Goemans, 2000), a point to which I return in the conclusion.
Formal models of crisis bargaining and war have the advantage of clearly specifying (a) who takes what decisions and why on the path to war, (b) the conditions under which we expect each mechanism to work, and (c) multiple implications that we can use to distinguish the working of some mechanisms from others. As such, they are uniquely valuable for sorting through possible explanations for important historical cases (see Goemans and Spaniel, 2016), like Russia's 2022 invasion of Ukraine. The contributions to this symposium take models to the data—i.e. to the historical record, incomplete though it is two years into the war—looking for key similarities that indicate that their chosen mechanism is in play, at times finding validation and at others ruling out candidate mechanisms. In that sense, this symposium represents an exercise in historical political economy (Gailmard, 2021), albeit one grappling with an incomplete and still-changing empirical picture.
Conclusion
Analyzing current history is difficult (Plokhy, 2023), but it is easier when we have well-understood, logically valid theories that imply their own evidence, which facilitates the sorting of potential explanations that is the very stuff of social science. The bargaining framework has given a common language to a set of causal mechanisms that explain the move from peace to war (see Powell, 2002; Schultz, 2012; Spaniel, 2024), allowing Smith (2024), İdrisoğlu and Spaniel (2024), and de Vogel and Sun (2024) to teach us not only about the Russo-Ukrainian War but also about the theory of war itself. By showing that the decisions leading up to the 2022 invasion can be rationalized with existing models, this symposium increases our confidence in the usefulness of the bargaining framework. And by developing a list of candidate mechanisms, they can also inform expectations about how the war will end. Whether fighting (a) solves a bargaining problem—information (Filson and Werner, 2002), commitment (Leventoglu and Slantchev, 2007), or both (Wolford et al., 2011)—or (b) eliminates a cost of peace, like preserving a government in power that would otherwise face personal punishment (Goemans, 2000) or generating a peace dividend (Powell, 2006: 192–194), we may see different patterns of both duration and the terms on which conflicts end. Further, places where the bargaining framework does not seem to fit also reveal areas where it can be refined, extended, or challenged (Zinnes, 1980). 6
Finally, the symposium suggests several potential contributions to the modeling dialogue. First, given Russia's demonstrated record of invading its neighbors, including Ukraine itself in 2014, to say nothing of 2021's public preparations for war, why did some countries seem to accept Russian claims that war was not in the offing? Why would a country send simultaneous and contradictory signals about its intentions, and which of those signals do receivers choose to act on? Second, Russia seems to have underestimated the resolve of Ukraine's Western backers. This recalls Wagner's (1993) account of World Wars I and II as caused by uncertainty about what coalitions would form to balance bids for continental dominance. The Russo-Ukrainian War, as well as other multilateral defenses of the status quo like resistance to Chinese attempts to control the South and East China Seas, points to the value of an extension of the bargaining framework to problems of collective deterrence, especially outside the context of extended deterrence. 7 Finally, the war has yet to expand, but it is worth asking whether and how it might. Americans, Chinese, and Soviets managed to prevent the Korean War from expanding with a set of tacit rules, i.e. no nuclear weapons and no combat outside Korea (Schelling, 1960, 76), but Ukraine is surrounded not by water on three sides but by other states supporting its war effort, including NATO members, and its backers disagree with Russia over more than just who should rule in Kyiv. How do conflicts with so many ostensible opportunities (Siverson and Starr, 1990) for expansion stay localized, when do interveners sign separate peaces (see Joyce et al., 2023), and when does intervention draw in other states (Powell, 2017)? The bargaining framework will be useful in answering all of these questions, and the continuing suffering in Ukraine highlights just how urgent it is to pursue answers to them.
