Political Institutions and Political Conflict: Alliances and Preventive War. Mark Souva msouva@fsu.edu Florida State University

Political Institutions and Political Conflict: Alliances and Preventive War Mark Souva msouva@fsu.edu Florida State University Abstract Do alliances prevent preventive war? Preventive war motivations are an important cause of interstate war. Recent research finds that alliances deter less intense forms of militarized conflict. Research is unclear on the relationship between alliances and war, particularly preventive war. I argue that militarily powerful alliances deter states with preventive war motivations from initiating war. Powerful alliances deter war by making war more costly for the attacking state. Absent powerful allies, potential attackers are less likely to believe war will be costlier than the expected loss of influence due to an expected shift in military power. A multivariate model shows some support for the hypotheses in both the pre-cold War and Cold War eras. Paper Prepared for the Political Institutions and Public Choice Conference, Durham NC May 2015. 1

Do alliances prevent preventive war? A significant body of research contends that preventive war motivations are central to explaining the outbreak of many wars (see e.g. Fearon, 1995; Powell, 2006; Bell and Johnson, Forthcoming). Perhaps the most famous statement on this topic is by AJP Taylor (1954: 166), who wrote: every war between the Great Powers [between 1848 and 1919] started as a preventive war, not a war of conquest. Another significant body of research finds that alliances deter conflict (see e.g. Leeds, 2003; Johnson and Leeds, 2011; Benson, 2011; Fuhrman and Sechser, 2014; Benson et al 2014). When combined, these two research programs raise a question: Do alliances prevent preventive war? On the one hand, defensive alliances should deter. If the alliance is credible, then it raises the cost of war for the attacker. On the other hand, defensive alliances are formed because of security concerns; thus, they may not deter but be an indicator that war is coming. In this context, the defensive alliance is endogenous to a hostile situation. Vasquez (1993) also contends that an alliance may not deter, but for a different reason. For Vasquez, an alliance is an example of power politics and such actions increase the probability of conflict; they are a step to war. I argue that most alliances fail to deter preventive war from occurring. They fail to deter war because they are not sufficiently powerful. Alliances form when there is some expectation of conflict. While almost any alliance may make war costlier for an attacker, to deter preventive war it is necessary to significantly increase the cost of war so that a challenger no longer believes it will prevail. A minor increase in the cost of war is not sufficient for deterrence to succeed. In the context of preventive war, a would-be attacker has a military advantage and expects to win should war occur. Alliances that simply make the outcome more difficult to achieve without altering the expected outcome are unlikely to deter. Yet if the alliance is militarily powerful, then 2

the alliance may significantly increase the cost of war and change the expected outcome of a conflict, making preventive war less likely. Alliances are often viewed as central to understanding the outbreak of major power war (see e.g. Snyder, 1991), and the argument advanced and findings presented here help explain variation in major power war in the 20 th century. Why did the major powers go to war in 1914 and 1939/1941 but not after that? I argue that World Wars I and II were preventive wars; the central bargaining problem leading to these wars was a credible commitment problem. Germany expected to lose its military advantage in the near future. This made war in the present attractive. In contrast, the major powers have avoided war with each other since the end of the Second World War. I contend that stems from them not facing significant credible commitment problems and that alliances are key to understanding why credible commitment problems have been less common since 1945. In particular, the North Atlantic Treaty Organization alliance, the Southeast Asian Treaty Organization alliance, and the Warsaw Pact alliance, among others, are central to understanding the lack of major war since 1945. Each of these alliances features a very strong ally, an ally with so much military power that credible commitment concerns are greatly reduced and actors are able to find a peaceful bargain. In the conclusion, I discuss how the alliances prior to World War I and World War II were not sufficiently powerful to prevent those preventive wars. The paper proceeds as follows. After situating this paper in the literature, I develop these arguments connecting certain types of alliances to deterrence in more detail. Then I present a research design to test the hypotheses, discuss the empirical results as well as limitations of the current research and what to do next. 3

Place in the Literature Both the core research question do alliances prevent preventive war and the primary hypothesis very powerful alliances prevent war but less powerful ones do not are novel. Research examining the effect of alliances on interstate conflict does not distinguish between credible commitment and informational mechanisms for bargaining failure. Moon and Souva (2014) distinguish between credible commitment and informational reasons for bargaining failure, but they do not examine the role of alliances and they only examine one reason for credible commitment problems. Early research examining the effect of alliances on conflict did not distinguish between different types of alliances or how militarily powerful the alliance was. Leeds (2003), Johnson and Leeds (2011), Benson (2011), and Wright and Rider (2014) all distinguish between different types of alliances, yet this body of work does not examine wars, only militarized interstate disputes. Perhaps the study closest to this research is by Johnson, Leeds, and Wu (Forthcoming). They measure the military capabilities in the alliance. This is critical for distinguishing between powerful and weak alliances. Yet they do not examine wars, which also means they do not focus on the preventive war context. Both of these are significant for it appears that alliances have one effect on MIDS and a different one on wars. Moreover, the bargaining context matters and their research does not take that into account. Most recent research examining the effect of alliances on conflict measures conflict as the occurrence, or initiation, of a militarized interstate dispute (MID) (Leeds, 2003; Johnson and Leeds, 2011; Benson, 2011; Fuhrman and Sechser, 2014; Wright and Rider, 2014). This body of research finds that some alliances (defensive or conditional deterrent) reduce the probability of a MID. Research in the steps-to-war program, however, measures conflict as the occurrence of a war, and this body of research tends to find that alliances are positively associated with war 4

(Colaresi and Thompson, 2005; Senese and Vasquez, 2005). But this body of research does not distinguish between types of alliances (e.g. offensive and defensive; conditional and unconditional deterrent), the strength of the alliance, or whether the central mechanism leading to war was informational or a credible commitment problem. These same limitations apply to other relevant research programs. Some work on power transition theory takes into account alliances, but this work does not distinguish between types of alliances (Kim, 1989, 1991). (While power transition theory does not explicitly distinguish between information and credible commitment problems, a charitable interpretation of that research program suggests that all major wars are caused by credible commitment problems, thereby obviating the need for a distinction between informational and credible commitment problems.) It is worth noting that this research finds that alliances do not deter. Finally, the small amount of empirical work on preventive war does not take into account alliances (Lemke, 2003; Bell and Johnson, Forthcoming). However, this research does show that preventive war expectations are statistically associated with war breaking out. Theory In the bargaining model of war, there are two general causes of bargaining failure leading to war, information problems and credible commitment problems (Fearon, 1995; Wagner, 2007; Powell, 2006). Since the publication of Fearon s essay, most theoretical (see e.g. Fearon, 1994, 1997; Schultz, 1998, 1999; Smith, 1998; Slantchev, 2005, 2006) and especially most empirical work has focused on information problems (see e.g. Schultz, 1999; Weeks, 2008; Uzonyi et al, 2012; Downes and Sechser, 2012). Yet increasingly research points to the importance of credible commitment problems for explaining war (see e.g. Slantchev, 2012). A credible commitment problem may occur for a variety of reasons: expectations of an immediate attack (i.e. pre- 5

emptive war), a first-strike advantage, an expected long-term and costly defense, expectations of a change in the other side s political leadership, issue indivisibility, bargaining over goods that affect future power, and expectations of a shift in power. I motivate the argument by focusing on the preventive war context but the primary conclusions hold regardless of the reason for the credible commitment problem. Preventive war occurs when a declining state believes it is better off attacking a rising state now than waiting for a worse deal, given an expected change in power, in the near future. Fearon (1995) summarizes the basic preventive war calculus as follows: δ(p2-p1) > Ca(1-δ) (Eq 1) Here delta (δ) is the expectation of future interaction, p2 is State B s (the rising state s) probability of winning in period 2, p1 is State B s probability of winning in period 1, and Ca is the cost of war for the declining state. If the left-hand side of the inequality is greater than the right-hand side, then preventive war is likely. Typically the major insight gleaned from this equation is that if the rising state s probability of winning in period 2 is much greater than its probability of winning in period 1, owing to an expected increase in military power, then preventive war may occur. The central question of this research is the following: How do alliances affect the preventive war calculus? To answer this question we need to distinguish between types of alliances, alliances with the declining state and those with the rising state, and the strength of the alliance. There are a variety of types of alliances. Both the Correlates of War (COW) and the Alliance Treaty Obligations Project (ATOP) distinguish between offensive, defensive, nonaggression, and neutrality pacts. ATOP also includes consultation pacts and whether the alliance has various conditions attached to it. Benson (2011) contends and finds that whether an alliance 6

is conditional or unconditional affects the decision-making calculus of attackers and defenders. In particular, only conditional defense pacts deter. I argue that only some defense pacts will deter preventive war. There is little reason to believe that a non-aggression or neutrality pact is likely to deter or embolden an attacker as they do not affect any of the parameters in the calculus. Offensive alliances with the declining state increase the incentive for preventive war. If the declining state with offensive allies does not attack today, then it is even more vulnerable in the future when it is relatively weaker and the alliance does not bind the allies to aid in defense. Offensive alliances with a rising state are also unlikely to deter. Knowing that a rising state has an offensive alliance makes a declining state value the present even more than the future. In the present, the offensive allies are not bound to aid the rising state if it is attacked; thus, the alliance has no immediate deterrence value. In the future, the rising state s bargaining advantage is extra strong. It will be stronger and with offensive allies it can credibly threaten to punish its opponent. In brief, offensive alliances are not likely to reduce the probability of preventive war, though such alliances with a declining state may further increase the likelihood of war. Defensive alliances with a declining state are unlikely to reduce the probability of war. On the one hand, it might seem that a declining state with defensive alliances has significantly less incentive to engage in preventive war than it otherwise would. A declining state is concerned about the future, but if it has strong allies to aid it in the event of an attack, then it should be less concerned. While this effect should be present, two other considerations are relevant. First, if a declining state s allies are very strong, then it is likely that the declining state itself is not a major power as most alliances tend to be militarily asymmetric. Countries that are relatively weak are not likely to be declining in power with respect to potential foes; they are likely to already be weaker. One may fear becoming even weaker, but there should be a small number of cases that 7

meet this condition. Second, if a declining state is strong, relative to its allies, then it not only fears the adverse shift in military power with its foe but also a decrease in autonomy benefits from its alliance. Relatively strong states receive some, if not more, autonomy benefits than security benefits from their alliances (Morrow, 1991). Thus, a declining state with defensive allies may have less reason to fear a future attack than a state without such allies but the future is costly to it both in terms of its decline vis-à-vis the rising state and with respect to its own allies. Since war is costly, these costs from relative decline may well be less making preventive war unlikely. Yet given what we know about the endowment effect (Tversky and Kahneman, 1981) it seems as likely that leaders will believe the costs of decline are greater than the cost of war, making preventive war more likely. Some defensive alliances with a rising state do reduce the incentive for war. The motivation for preventive war is usually thought of only in terms of the expected shift in power. With this focus in mind, whether the rising state has defensive allies or not is irrelevant. But the preventive war calculus also depends on the declining state s expected cost of war today. This is where the rising state s defense pacts alter the probability of preventive war. The cost of war for a declining state increases when a rising state has strong defensive allies. A declining state would rather fight a rising state with no allies or weak allies than one with very strong allies. Strong allies, for the rising state, decrease the incentive for preventive war. Under what conditions is one actor likely to believe another s defensive alliances will increase its cost of war? The allies have to be strong. A rising state with weak allies may not be able to deter a declining state for they will not alter the cost of war enough. Given the tendency of states to bandwagon with the system leader (see e.g. Organski and Kugler, 1981), it may be that many rising states are not able to attract strong allies to prevent preventive war. Stated 8

differently, but with the same implication, a rising state may have difficulty attracting allies when it is commonly known that war with a strong country is a serious consideration. As discussed in more detail below, this helps account for the outbreak of World Wars I and II. The above arguments lead to the following hypothesis. Hypothesis 1: When preventive war motivations are high, the probability of preventive war decreases with the military strength of the rising state s allies. Research Design Central to this research is the distinction between potential attackers and potential defenders. The independent variable of interest, powerful defensive alliances, is only expected to reduce the probability of war for rising states. With this in mind, the unit of analysis for this research is the directed-dyad year. Empirical research on international conflict often analyzes the initiation of a militarized interstate dispute (MID). MIDs are threats, shows, displays, or uses of force. The vast majority of MIDs are not wars, as conventionally defined (1000 battle deaths). A primary benefit, then, of analyzing MIDs is that there are more to analyze. Yet our theories typically focus on war as the outcome variable of interest. This is the case with the bargaining model of war. Accordingly, this research examines wars as the outcome variable and uses data from the Correlates of War project (Sarkees and Wayman, 2010). Most empirical models of war include joiners, for both the initiating and target sides. Since the focus here is on alliances, this is especially appropriate. For example, if State A is contemplating war with State B and State B has a defense pact, then State A knows that it is likely going to war against both State B and its allies. 1 1 In sensitivity analyses, I examine only original participants and joiners for the target side but not the initiating side. 9

One objection to a focus on wars is that they are the outcome of a process and by looking at the end of the process one may not properly assess the effect of an independent variable on that process. The balance of power, for example, may have one effect on the occurrence of a conflict but another effect on the escalation of that conflict to war (Fearon, 1994). However, a multistage research design requires a clear theory about the effect of an independent variable on different stages of conflict. In this case, the theory does not make predictions of that sort. If anything, the predictions are about the outcome of war, not MIDs. In addition, empirical research modeling the process leading to war still arbitrarily chooses stages. Why should the outbreak of a MID be the first stage modeled? Why not the outbreak of an issue claim or diplomatic dispute? This body of research is also not clear about precisely how to model the process. Should ongoing disputes be included or not? Together the lack of a clear theory for focusing on MIDs instead of wars and the empirical concerns with how to empirically model the selection process suggest that using wars as the outcome measure is appropriate. 2 Finally, it is worth noting that research examining preventive war has employed a research design similar to the one here (Lemke, 2003; Bell and Johnson, forthcoming). The primary independent variable of interest is capable defensive alliances. A capable defensive alliance is defined as a defensive alliance that is militarily strong. This requires identifying all defensive alliances that State B, the potential target, has with obligations to aid B in the event of an attack by State A. In other words, many alliances identify specific foes and allies are not bound to enter a conflict if the attacker is someone different than identified in the alliance. Practically speaking, this means State B may have some allies that are not relevant for 2 Braithwaite and Lemke (2011) provide an excellent discussion of the sensitivity of Heckman selection models in the context of international conflict. 10

understanding a potential conflict between A and B. Johnson and Leeds (2014) and Johnson, Leeds, and Wu (Forthcoming) have identified all relevant alliances for each directed-dyad. Further, Johnson, Leeds, and Wu aggregate the military power of the allies where military power is defined as the Correlates of War Composite Capabilities Index. I use their data for the Alliance Power variable. Alliance power is the ratio of State B s power plus its relevant allies power to the power of States A, B, and all relevant defensive allies for B. The variable ranges from zero to one with higher values indicating that State B and its allies have a greater probability of prevailing in a conflict. Now it is not straightforward exactly how much power the target and allies need to prevent preventive war. Equal power or a slight power advantage for the target may not be sufficient. Based on the theory, however, we would expect to observe support for Hypothesis 1 when the target and its allies are significantly stronger than the challenger. In other words, it is not entirely clear if the relationship between alliance power and war is linear or holds only at high values of alliance power. To guard against non-linearity in the data and examine the relationship for the most relevant set of cases, I employ a binary variable. Specifically, Target s Allies Power is equal to one if the target and allies power is five times or more greater than the challenger s power. 3 In addition to the presence of militarily powerful defensive alliances, other factors affect the probability that one state will initiate a war against another state. I control for the following potential confounders: the expected reliability of the alliance, the regime type of each state and regime similarity, foreign policy affinity, geographical proximity, and conflict history. 4 3 The findings in the pre-1942 period hold when the target and its allies power is three times as great as the challenger. This is not the case in the post-world War II era; five times the challenger s power seems to be the cutpoint. 4 Unless otherwise noted, data for the control variables was generated from EUGene (Bennett and Stam, 2000) v3.204. 11

The reliability of an alliance may be central to explaining whether the alliance has an effect on the outcome. It may be the case, for example, that alliances expected to be unreliable will not deter but alliances expected to be reliable will deter. Johnson, Leeds, and Wu (Forthcoming) suggest an alternative relationship between reliability and deterrence. 5 Credibility is more important for deterrence when the alliance is relatively weak. Capability and credibility are not complements but substitutes. For the primary analyses, I do not interact Target s Allies Power and Alliance Reliability, but this relationship is explored in sensitivity analyses. Alliance Reliability is measured as the similarity in foreign policy portfolios between State B and its allies. Data come from Johnson, Leeds, and Wu. To measure each country s political institutions and the relationship between each state s political institutions, I draw on work by Bennett (2006). In recent years, a body of research has established that there is (a) a democratic peace, (b) a weaker but still relevant autocratic peace, and (c) a democratic initiator peace. Bennett refers to the first two as the joint coherence peace, that is, two countries that are institutionally coherent and similar (either a positive or a negative ten on the Polity democracy index) share a separate peace. To account for all of these known empirical regularities, I include the following variables: State A Democracy, State B Democracy, Joint Democracy, Joint Democracy Squared, and State A Democracy*Political Similarity. All measures are based on the rules described in Bennett (2006). Data come from the Polity IV project (Marshall and Jaggers, 2002). Affinity is a measure of the alliance portfolio similarity between the two states in the dyad, weighted by the Correlates of War capability index. I use the S version of this variable 5 In sensitivity analysis, I substitute military institutionalization for portfolio similarity as the measure of expected reliability. The more institutionalized the alliance, the greater the expected reliability. This measure is based on Leeds and Anac (2005) and is also used by Johnson, Leeds, and Wu (Forthcoming). 12

(Signorino and Ritter, 1999). Higher values indicate more similar foreign policies. I include two measures of geographic proximity, contiguity and distance between capital cities. Contiguity equals one if the states are contiguous by land or separated by less than 400 miles of war, zero otherwise. Distance is the natural log of the great circle distance between capital cities. Finally, I include three variables to address the conflict history of the dyad and temporal dependencies in the data. The variable Peace Years is a count of the number of years since the last COW war. Peace Years Squared and Cubed are straightforward (see Carter and Signorino, 2010). The empirical domain of this study spans all directed-dyads in which there is (a) a high level of preventive war motivations and (b) a relevant defense pact for the period 1816-2000. 6 The focus on dyads with a preventive war motivation is unique. The primary reason for limiting the analysis to this set of dyads is theoretical. It is not clear, for example, that a potential initiator with defensive allies will be more likely to initiate a war when preventive war motivations are low. In this context, instead of credible commitment problems being central to the bargaining dynamic, information problems take center stage. Deterrence is still relevant to understanding bargaining failure as a result of an information problem, but generally such failures stem from asymmetric information on resolve. Thus, the expected reliability of the alliance probably matters more when preventive war motivations are not high. In addition to these theoretical considerations, an empirical focus on preventive war contexts is important. As noted earlier, credible commitment problems, and preventive war in particular, seem to be very important causes of war, yet they have received little empirical attention. If nothing else, this is an interesting subset of cases. 6 In sensitivity analyses, the models are run only on politically relevant dyads. Results are similar. 13

When are preventive war motivations high? When should State A expect an adverse relative power shift with respect to State B in the near future? Lemke (2003) examines changes in relative power over the last twenty years. The more one state is declining in power relative to another the greater the preventive war motive. Lemke s analysis shows little empirical support for preventive war motivations being positively related to war. Bell and Johnson (Forthcoming) note that preventive war motivations are based on expectations about the future. Changes in power in recent years should already be incorporated into the bargaining status quo and therefore are unlikely to trigger a preventive war. Accordingly, they calculate each country s future power (one, three, and five years into the future) and then the expected change in relative power in the dyad. Bell and Johnson find robust support for their measure of expected shifts in power and the outbreak of war. Notwithstanding the merits of the Bell and Johnson approach, their measure depends heavily on a sound model of military spending. With a variety of models of military spending available, one would want to examine the sensitivity of their results to different models. Also, they do not predict military spending per se, but a state s share of military power (the two military components of the COW capabilities index). It is not clear that models of military spending are appropriate for predicting a country s share of these components. Finally, it is also unclear that such a measure, or thought process, is used by decision-makers. It seems likely that decision-makers use a simpler rule of thumb. I turn to one such possibility. Preventive war motivations are a function of relative militarization levels, where a militarization advantage indicates a greater motivation for preventive war. I use the COW capability data to measure militarization. A country s militarization is the difference between its military share and the average of its economic and demographic share. A high value on this variable means a country is more militarized than its basic economic and demographic attributes 14

would suggest. I define preventive war motivations as the difference between each country s militarization score, where higher values indicate a greater motivation for preventive war. The logic works as follows. It is relatively easy for State A to know if it is more militarized than State B. If State A is more militarized than it has reason to believe that State B will increase its level of militarization, for State A has militarized more based on the same inputs. If State B increases its level of militarization, then State A either has to increase its level, and it is already more militarized, or suffer a decrease. To avoid the extra expenditure, State A may choose preventive war. 7 Next, I classify a dyad as having a high preventive war motivation if the relative militarization measure is in the top quartile. Empirical Analysis First, I examine whether the preventive war measure is correlated with war. If there is little empirical support for the preventive war measure, then splitting the sample for the subsequent analyses is less persuasive. I do, however, find a statistically significant and positive relationship between preventive war motivations and the initiation of war (see Table 2 in Appendix A). About 38% of dyads in the pre-1942 period have high preventive war motivations, but they account for about 60% of all war initiations. After World War II, dyads with high preventive war motivations account for about 25% of the sample and 44% of war initiations. Table 2 shows coefficient estimates for a multivariate model of war initiation. The addition of likely confounders does not change the statistical relationship between preventive war expectations and war initiation. Given the known lack of major power war in the latter era and 7 In sensitivity analyses, I explore a variety of variations on this basic measure. For example, do preventive war motivations hold for all dyads or only when one state is militarily stronger? Do preventive war motivations hold for all dyads or only dyads in which there is some expectation of hostility or future conflict? Does militarization depend on both economic and demographic attributes? Should these attributes be weighted equally? I also examine different cutoffs for the high preventive war motivation. None of the main findings change. 15

the existence of nuclear weapons, there is some reason to believe that preventive war motivations may only be relevant for earlier historical periods. The analysis shows that preventive war is still a relevant concern today. Substantively, a dyad with preventive war motivations is about 88% more likely to experience war than a dyad without such motivations prior to the Cold War and about 110% more likely to experience war after 1945. The main empirical results are presented in Table 1. To guard against temporal treatment effects (Clark and Nordstrom, 2003), particularly whether the post-world War II era is different than the earlier period, I estimated separate models on the 1816-1945 and 1946-1991 time periods. For Hypothesis 1, the key parameter estimate of interest is on the term, Target s Allies Power. It is negative and statistically significant, as expected by the hypothesis. Although the major focus here is on the statistical significance of the parameter, it is worth discussing the substantive effect. The variable Target s Allies Power reduces the probability of war by about 71%. 8 By comparison changing the domestic political institutions in the two states from mixed autocratic-democratic to both fully democratic reduces the probability of war by about 96%. In the 1816-1941 period, about 56% of the cases, potential targets, have an ally that makes the target and allies power at least five times the power of the potential initiator, yet only 25% of all war initiations in the sample occur in this context. The results are similar for the post-world War II era (see Model 2 in Table 1). Target s Allies Power is again statistically significant and negative. In this sample, when the potential target and its allies are five times stronger than the challenger, the probability of war decreases by about 62%. Moreover, an examination of the number of cases with a strong ally (or allies) 8 Changes in predicted probability were calculated using Clarify (King, Tomz, and Wittenberg, 2000). All variables were set at their mean or median, except for the variable of interest which was changed from zero to one. 16

suggests why the post-world War II period has seen a decrease in interstate war. About 83% of all potential targets have an alliance such that the power of the target and its allies is at least five times as great as the potential initiator s power. Since more countries now have powerful allies (e.g. the NATO, SEATO, Warsaw Pact, etc), it is perhaps not surprising that war has decreased. The ability of powerful alliances to reduce the probability of war is all the more noteworthy considering the context. The context is dyads with high preventive war motivations. Powerful alliances, then, are reducing the probability of war among dyads that are relatively more likely to go to war than other dyads. Further Analysis Further analysis of the post-world War II era suggests that the central factor of interest is not Target s Allies Power per se but alliances with nuclear weapons. I re-ran Model 2 replacing Target s Allies Power with a binary variable equal to one if at least one of the alliance partners possessed nuclear weapons. This variable, Nuclear Capable Ally, is statistically significant and negative. When a state has an ally with nuclear weapons, preventive war is unlikely to occur. Moreover, the model with the Nuclear Capable Ally model outperforms (i.e. has a lower loglikelihood, AIC and BIC) the model with Target s Allies Power. If both variables are included, then Target s Allies Power variable becomes statistically insignificant while Nuclear Capable Ally is still significant and negative. Nevertheless, the two variables agree in about ninety percent of cases. The sample for Models 1 and 2 only includes directed-dyads for which there is a relevant defensive alliance. With respect to the independent variable, then, we are comparing alliances with a lot of power versus alliances with only some power. In all cases, there is an alliance. This 17

is a difficult test for the hypothesis for anytime an alliance is present there is some expectation that it will contribute to deterrence. Moreover, because alliances form when security concerns are present, one might expect that military conflict is more likely in this sample. This selection process makes it less likely to find support for the hypothesis advanced in this research. Nevertheless, some countries may fail to form an alliance because conflict is probable and potential allies do not want to go to war. Do strong allies reduce the probability of war when we examine all dyads with preventive war motivations? Table 3 shows model results that address this question. For both the pre-1942 and post 1945 periods, the data is consistent with the hypothesis: a strong alliance reduces the probability of preventive war. An examination of the countries with powerful alliances that deter others with preventive war motivations sheds light on the multivariate analysis. In the post-world War II period, some of the targets meeting these criteria that are not attacked, despite being under-militarized, are Japan, Turkey for many years but not all, and a number of Western and Eastern European countries. Japan, Turkey, and the Western European countries were allied with the United States; the Eastern European countries that were under-militarized were allied with the Soviet Union. Powerful allies, particularly nuclear capable ones, appear to enhance deterrence. This carries an important policy implication. To reduce the probability of war, countries do not necessarily need to develop nuclear weapons. All they need is an ally with nuclear weapons. Based on the measure presented here, Germany had preventive war motivations in 1914 and 1939. Further, the alliances arrayed against Germany were not sufficiently strong to deter Germany from attacking. The combined CINC scores for the Germany & Austria-Hungary alliance is.226, while the combined CINC scores for the Triple Alliance of France, Russia, and the United Kingdom is.321. The latter alliance was only a little stronger based on these 18

numbers, and based on the empirical results presented here not nearly strong enough to deter Germany s preventive war motivations. If the United States would have allied with Great Britain and the others, then it is possible that World War I could have been prevented as the alliance would have been more than twice as strong as the Entente. Instead of blaming alliance politics for the expansion of World War I, it may be more accurate to blame politics for preventing certain alliances that could have prevented that preventive war. Alternatively, if these countries would have armed more in peacetime, then these wars may have been avoided. In the post-world War II period, wars that could potentially have been deterred include the Korean War, the Iraq-Iran war in the 1980s, and the Iraq attack on Kuwait in 1990. The Iraq- Iran War is sometimes described as a war of opportunity. Saddam Hussein saw that the revolution in Iran weakened the country temporarily so he attack while conditions were ripe. What this research adds is that the primary factor motivating Saddam s thinking was not what happened inside Iran but the loss of American support for Iran. The Iraq-Kuwait war of 1990 may have been easier to prevent. Ambassador Glaspie s words would have been less ambiguous if the U.S. had a defense pact with Kuwait. A similar story describes the Korean War. Secretary of State Acheson inadvertently signaled to North Korea that South Korea was not critical to the U.S. geopolitical strategy. One implication of the Kuwait and Korean wars is that institutions are better at deterring than diplomacy. Conclusion This research examines whether alliances can prevent preventive war. Preventive war, or war motivated by expectations of a change in military power, are a statistically significant predictor of war initiation. At the same time, a large body of research indicates that alliances, at least certain types of alliances, deter others from attacking one s allies. I argue that militarily 19

powerful alliances will deter preventive war. I find support for the primary hypothesis of this research in multiple time periods and samples. In the pre-cold War era, powerful alliances decrease the likelihood of a war. Further, it appears that one of the reasons for the outbreak of World Wars I and II is that the alliances arrayed against Germany were not sufficiently strong. This research does not address whether the alliances contributed to the expansion of the war, but it does suggest that the alliances in place in 1914 and 1939/1941 were not strong enough to deter Germany from launching a preventive war. Since the end of the Second World War, there has been an increase in powerful alliances and, I argue, this has contributed to the relative peacefulness in this era. Powerful alliances since 1945 are associated with countries possessing nuclear weapons, but as the pre-1942 analysis makes clear, nuclear weapons are not the only way to make preventive war too costly to undertake. There is still much research to do on this topic. Further work is needed on the theory. Is an examination of MIDs and escalation to war the appropriate way to assess the deterrent effect of alliances? Should one expect an interactive relationship between alliance power and alliance credibility? Are these factors complements or substitutes? Is the theoretical motivation for distinguishing between dyads with a high preventive war motivation and those with a low preventive war motivation a sufficient reason for separating sample? Would different results obtain if the measure of preventive war was different? These are only a few of the questions to investigate in further work. Nevertheless, the current research suggests two interesting aspects of the causes of war. Preventive war motivations are often relevant to explaining war initiation, and political institutions are sometimes a force for peace. A country with very strong allies is much less likely to be the target of preventive war than a country lacking powerful allies. 20

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TABLE 1 MULTIVARIATE ANALYSIS OF ALLIANCE POWER AND WAR INITIATION IN DIRECTED- DYADS WITH A RELEVANT DEFENSE PACT Model 1: 1816-1941 Model 2: 1946-2000 b/se b/se Target s Allies Power -1.364** -1.224** (0.515) (0.677) Alliance Reliability -1.332-1.319 (1.172) (1.051) Initiator s Alliance Power 6.372*** -1.943 (1.455) (2.316) Democracy A -0.217* 0.014 (0.093) (0.080) Democracy B -0.014-0.013 (0.063) (0.052) Joint Democracy -0.024* -0.010 (0.010) (0.016) Joint Democracy 2-0.000 0.000 (0.000) (0.000) Democracy A x Similarity 0.013-0.012 (0.007) (0.008) F.P. Affinity -0.161-1.420 (0.630) (1.310) Ln (Distance) -0.133-0.925*** (0.349) (0.209) Contiguity 0.847 0.018 (0.677) (1.077) Peace Years 0.098-0.137* (0.074) (0.055) Peace Years 2-0.002 0.003** (0.001) (0.001) Peace Years 3 0.000-0.000** (0.000) (0.000) Constant -6.361* 2.134 (2.648) (2.656) N 6270 135,034 BIC 387 465 * p<0.05, ** p<0.01, *** p<0.001, one-tail significance test. Standard errors clustered on the directed-dyad. 25

Appendix A: Sensitivity Analysis TABLE 2 MODELS WITH PREVENTIVE WAR MOTIVATIONS AS AN INDEPENDENT VARIABLE, ALL DIRECTED DYADS Model 1: 1816-1941 Model 2: 1946-2000 b/se b/se Preventive Motivations 0.615** 0.698** (0.192) (0.268) Democracy A -0.022-0.000 (0.034) (0.052) Democracy B 0.027 0.004 (0.023) (0.039) Joint Democracy -0.006-0.006 (0.004) (0.006) Joint Democracy 2-0.000-0.000 (0.000) (0.000) Democracy A x Similarity 0.000-0.007 (0.003) (0.004) F.P. Affinity -1.829*** -0.548 (0.257) (0.404) Contiguity 2.141*** 2.019*** (0.345) (0.396) Ln (Distance) 0.060-0.727*** (0.152) (0.123) Peace Years 0.050* -0.102*** (0.022) (0.020) Peace Years 2-0.001** 0.002*** (0.000) (0.000) Peace Years 3 0.000** -0.000*** (0.000) (0.000) Constant -7.535*** -2.166 (1.254) (1.184) N 186,231 797,560 BIC 2403 1650 * p<0.05, ** p<0.01, *** p<0.001, two-tail significance test. Standard errors clustered on the directed-dyad. 26

TABLE 3 MULTIVARIATE ANALYSIS OF ALLIANCE POWER AND WAR INITIATION IN DIRECTED- DYADS (ALL DYADS WITH HIGH PREVENTIVE WAR MOTIVATIONS) Model 1: 1816-1941 Model 2: 1946-2000 Target s Allies Power -0.683-0.922 (0.329)** (0.322)** Alliance Reliability 2.288-0.442 (0.968)* (0.871) Initiator s Alliance Power 6.241 1.909 (1.120)** (1.285) Democracy A -0.012 0.031 (0.047) (0.089) Democracy B 0.039 0.003 (0.030) (0.071) Joint Democracy -0.005-0.008 (0.005) (0.011) Joint Democracy 2-0.000-0.000 (0.000) (0.000) Democracy A x Similarity 0.000-0.011 (0.004) (0.007) Ln (Distance) 0.168-0.789 (0.168) (0.170)** Contiguity 2.114 1.326 (0.389)** (0.596)* Peace Years 0.116-0.109 (0.032)** (0.028)** Peace Years 2-0.003 0.002 (0.001)** (0.001)** Peace Years 3 0.000-0.000 (0.000)** (0.000)** Constant -11.523 0.026 (1.775)** (1.946) Log Likelihood -634.67-309.80 N 66,815 201,082 * p<0.05, ** p<0.01, *** p<0.001, one-tail significance test. Standard errors clustered on the directed-dyad. 27