Dan Lindley and Ryan Schildkraut¹

“Is War Rational?

The Extent of Miscalculation and Misperception

as Causes of War”

“By every rational standard, North Korea should still be deterred. In practice, however, few wars are the result of rational calculations, managed crises, and highly intellectual escalation ladders.” (Cordesman, 2002)

“War seems to many to be an irrational act of passion....Yet for all the emotion of the battlefield, the premeditation of war is a rational process consisting of careful and deliberate calculations.” (Bueno de Mesquita, 1981, 19)

Who is right?

ABSTRACT

Is war a rational, well-calculated pursuit of states, or is war more often caused by miscalculation and misperception? Assumptions about the extent of rationality underlie policy debates on subjects ranging from deterrence to missile defense. The rationality assumption also divides theorists and theories on the causes of war into two camps. For example, many realists and expected utility theorists fall into the rationalist camp, while political psychologists and students of bureaucratic politics fall into the miscalculation and misperception camp. Despite this schism, few studies empirically test the overall extent of rationality in decisions for war. Using our “Is War Rational?” database, we find that prior to 1900, war initiators won over seventy percent of the time. Since 1945, only about one-third of initiators win. Assuming that states initiate wars planning to win, the utility of war has declined dramatically, and miscalculation and misperception have come to dominate decisions for war. Deterrence is getting harder. The utility of rationalist approaches to the causes of war is decreasing. Causes of miscalculation and misperception deserve more study.

Introduction

Is war the rational and well-calculated pursuit of states, or are decisions for war more often dominated by miscalculation and misperception? This is an important question because assumptions about the extent of rationality in decisions for war underlie policy debates on a range of subjects from deterrence and missile defense to peacekeeping. Arguments about rationality also underlie academic debates about the general causes of war and the methodologies to study them, as well as historical debates about the causes of specific wars.

If one assumes that states start wars intending to win them, then losses by war initiators will tend to indicate that the decision for war was dominated by miscalculation and misperception. This assumption means that the extent of miscalculation and misperception can be measured by looking at the win and loss rates of initiators.

Using the Correlates of War (COW), Militarized Interstate Dispute (MID), and National Material Capabilities (NMC) databases, and we find that initiators won 55% of the seventy-nine large interstate wars between 1815 and 1991. The utility of war has declined markedly over time. In the forty-seven wars since 1900, the success rate declined to 43%. Since 1945, initiators won 33% of twenty-three wars. Despite declining win rates, states initiate wars at an increasing to steady (since 1920) rate over time. States are not learning that war increasingly does not pay.

Declining win rates and steady initiation rates provide the main basis for our core argument: miscalculation and misperception are increasing. This argument is bolstered by other findings showing that, for example, relative power is often not a good predictor of outcomes.

These findings have impacts across a range of policy and academic debates. If miscalculation and misperception is increasing, then deterrence is getting harder. The utility of rationalist approaches to the causes of war is decreasing. Causes of miscalculation and misperception deserve more study.

We begin by reviewing some of the policy and scholarly debates that hinge on assumptions about rationality in decisions for war. Second, we situate ourselves in the large-N literature on the causes of war, noting that the study of miscalculation and misperception is neglected in this literature, as is the study of war outcomes more generally. Third, we turn to methodological issues. We explain and justify the assumption that initiators intend to win their wars, define our terms, examine the major problems posed by the available data, and explain the decisions rules we adopted to respond to these problems. In addition, there is a technical appendix available online at: <<author website>>, where readers will also find the master data and analysis spreadsheets. Fourth, we present our findings, using descriptive statistics to demonstrate the declining win rate for war initiators, to see if power or allies help determine war outcomes, and to look at trends in the rate of war initiation. Finally, we discuss the implications of our findings for policy makers and scholars.

Debates that Hinge on Assumptions about Rationality

Assumptions about rationality underlie a number of policy and scholarly debates. For example, those who argue that deterrence works well assume that decisions to initiate war are rational and deliberate. If states are generally rational, then policy makers can effectively use arms, alliances, and deployments to increase the costs of war and bolster deterrence. On the other hand, arguments for greater transparency, for arms control, and against militarism and hypernationalism often assume that war is rooted in miscalculation and misperception. In this view, deterrence is harder because opacity, arms races and spirals, and malignant sources of misperception may cause unnecessary or inadvertent wars. Supporters of U.S. missile defenses often argue that ‘rogue’ states are irrational and not deterrable. Opponents of missile defense counter that ‘states of concern’ are deterrable. Light peacekeeping assumes that combatants do not really want to fight, and that peace can be kept once miscalculations and misperceptions are sorted out. Yet if the combatants have good reasons for fighting, peacekeeping must be heavy or avoided altogether (Betts 1994). Successful prescriptions for reducing the likelihood of war depend on accurate diagnoses of the causes of war. These diagnoses in turn often rely on assumptions about the prevalence of rationality and the quality of deliberation in the lead up to war.

Differing assumptions about rationality constitute a large but usually implicit debate in the causes of war literature. Most offensive and neo-realists, rational choice analysts, and materialists argue that war tends to be rational and deliberate. In contrast, some defensive realists, students of bureaucratic and organizational politics, and political psychologists argue that miscalculation and misperception tend to cause war. Using a broad brush, Table 1 shows how most general theories about the causes of war can be sorted into two camps according the assumptions they hold about the rationality of war.^[1]

Table 1: Parsing Causes of War by the Rationality Assumption
Theories and Schools Emphasizing Rational Causes of War	Theories and Schools Emphasizing Miscalculation and Misperception
Offensive Realism	Organizational and Bureaucratic Politics
Neo-realism	Militarism
Lateral Pressure Theory	Hypernationalism
Expected Utility Theory	“Cult of the Offensive”
Rational Choice Explanations	Psychology and Decision-making Models
Power Transitions, Preventive, and Pre-emptive Wars	Domestic Politics (including Scapegoating and Logrolling)
Resource Wars	Defensive Realism
Imperialism/Mercantilism	Spiral Model
Rational Deterrence	Optimistic Miscalculation
	Ancient Hatreds
	Weak Deterrence

The first camp contains rationalists who contend that states choose war for gains in security, wealth, and power, as they maximize utility in the face of systemic constraints and opportunities. Here we find assumptions and arguments about why states start wars for strategic reasons and with reasonably rational decision-making processes. The second camp contends that states are led to war because of internal pressures, misperceptions, spirals, and so forth. Here we find assumptions and arguments about states starting wars for non-strategic motivations and/or with distorted strategic calculations.

Despite many strong arguments on both sides of the schism, there is little sustained and explicit intellectual combat between the camps and very few scholars have investigated the overall extent of rationality in decisions for war. A rare example of protracted debate is the rational deterrence debate of the late 1980s and early 1990s (Achen and Snidal 1989; Downs 1989; George and Smoke 1989; Huth and Russett 1990; Jervis 1989b; Lebow and Stein 1989; Zagare 1990, among others). There is also work that contrasts rational choice and psychological models, with some consensus that the two approaches are complimentary (Geva and Mintz 1997; Levy 1997; McDermott and Kugler 2000; Quattrone and Tversky 1988).

Just as general causes of war can be parsed into the table above, debates about the causes of specific wars often turn on arguments about rationality versus miscalculation and misperception. The best example is the literature on World War I. Copeland and Fischer blame deliberate German policy (2000; 1967). In contrast, Snyder and Van Evera argue that WWI was caused by a web of misperceptions which they file under the rubric “cult of the offensive” (1984; 1985, 1999). Levy runs up the middle, arguing for a fairly subtle form of miscalculation: many of the Great Powers wanted a limited war prior to WWI, but that the huge scale of WWI was not what they intended or predicted (1991). In the debate over the Japanese decision to attack Pearl Harbor, Ienaga (1978) contends that Japan had fallen into the grip of militaristic hypernationalism while Sagan (1988) holds that Japan rationally weighed its choices and chose war. In assessing Saddam Hussein’s decisions to go to war in 1990/91, Pollack argues that Saddam, although a risk-taker, was not irrational or suicidal and had successfully been deterred in the past (2002, 248). On the other hand, Baram states that Saddam and his government had been irrational, prone to take unreasonable risks, and made many colossal errors in judgment (1992). Stein believes that Saddam stayed in Kuwait because of an unfounded belief in an American conspiracy to destroy him (1993).

Even critiques of specific books reflect the "Is War Rational?" debate. Perhaps the core of Betts’ 1999 review of Van Evera’s Causes of War (1999) is Betts’ view that Van Evera is wrong to argue that war is most often explained by miscalculation and misperception. Instead, Betts contends that states choose war because there are political and economic stakes that are worth war for the combatants. It was this disagreement between Betts and Van Evera that motivated the "Is War Rational?" project, and led to the question: what is the extent of miscalculation and misperception in decisions for war?

The Large-N Literature, War Outcomes, and Miscalculation and Misperception

Few scholars in any methodological tradition have attempted to test the overall extent of miscalculation and misperception in decisions for war. The main reason for this gap is that scholars who emphasize miscalculation and misperception tend to do case studies, while large-N scholars tend not to assess miscalculation and misperception. For example, in Geller and Singer’s review of the findings of 500+ large-N analyses on the causes of war, they claimed that miscalculation and misperception are important, but they then cast aside the issue by arguing that the subject can best be examined with case studies (1998, 44; see also Vasquez 2000 and Geller and Singer 1998, 192). Case studies are critical for understanding the mechanisms and processes leading up to specific wars, yet large-N analysis is often more persuasive for discerning overall patterns about war (Collier, Brady, and Seawright 2004, 253).

As noted by Stam in the beginning of his book on war outcomes, the large-N community has also largely neglected this issue (1996, 1). Most large-N studies focus instead on factors which correlate with war outbreak. Yet the study of outcomes is crucial for two reasons. First, success in war is the best way to judge the utility of war. The more initiators win, the higher the expected utility of war.

The second reason to study war outcomes is to learn more about the predictability of these outcomes. The extent to which war is a calculable bet or a large role of the dice speaks directly to the utility and rationality of engaging in war. For example, relative power should be one of the most powerful predictors of war outcomes. As the NMC documentation makes clear, relative power is not easy to measure, but it is easier than strategy, morale, domestic politics, or other more elusive determinants of outcomes (2004). If relative power is a good predictor of outcomes, this should reduce miscalculation and misperception and help deterrence. On the other hand, as the ability of relative power to predict war outcomes declines, war outcomes must then increasingly depend on more elusive variables. This in turn increases the odds of miscalculation and misperception. In sum, aggregate win/loss ratios provide a first cut at judging the utility of war. Predictability of outcomes then tells us more about the utility of war as a policy tool.

The major goal of this study is to use large-N analysis to assess the extent of miscalculation and misperception. We cannot assess individual instances or aggregate amounts of cognitive bias or bureaucratic politics, or any of the individual groups of causes of war in the left (rational) or right (miscalculation and misperception) columns in Table 1, above. However, we do claim that war increasingly results from miscalculation and misperception.

Several scholars have touched on or explored the substance, arguments, and methods of this article. Stam (1996) and Goemans (2000) look at war outcomes as a function of domestic politics, while Reiter and Stam (2002) argue that democracies are better at picking winnable wars, thus linking regime type to outcomes. Fortna (2004) notes that increasing numbers of wars are ending in ties, and is developing and testing hypotheses to explain why.

Others have looked at how initiator success rates change over time. In particular, Wang and Ray (1994) use a dataset of 105 great power wars going back to 1495 to discuss the rationality of decisions to go to war. They find that “initiators have been ‘significantly’ more likely to win than their targets…in the 19^th and 20^th centuries” with win rates of 56%, 52%, 53%, 74% and 67% in the five centuries from 1495 to 1991 (150, 145). Instead of using these findings to establish a trend and to argue that the rationality of war has increased (roughly) over time, they conclude by saying that the variation in win rates offers support to both the rationalist and miscalculation and misperception camps. In assessing all wars instead of great power wars, we find the win rate declining over time.

We build on this useful study in several ways. We gain leverage by looking at all major interstate wars, not just great power wars. By looking at 79 wars over the last 200 years, instead of 108 wars over 500 years, we reduce the N somewhat, but increase temporal commensurability between the wars. We examine the influence of relative power and joiners in more depth, and we keep our focus on the issue of the rationality of war.

Methods: The Key Assumption, Definitions, Data, and Coding Rules

The Key Assumption

To evaluate the “Is War Rational?” question, we begin by assuming that states start wars intending to win. When initiators win, we assume that states have correctly calculated, and made a rational choice. A loss indicates a miscalculation and/or misperception of some sort. Together, we call this set of assumptions and arguments our key assumption.

Our justification for this assumption starts with Clausewitz’s definition of war. War is a strategic interaction rooted in hostile intent, and chosen for political/policy goals which can be met by compelling the enemy through force (Howard and Paret, 1976). The goals of war are to increase a state’s power, security, and/or wealth, and these goals are things that can be won or extracted by successful compellence. States that use war to pursue these goals behave according to what we term Clausewitzian rationality.

We are making assumptions about state preferences and the process of pursuing those preferences. For preferences, we assume states are using war to pursue goals of power, security, and wealth. For process, we assume a rational decision making process exists if a state achieves its goals. In a rational process, there is at most a modest amount of miscalculation and misperception, initiators make reasonably robust calculations, and they choose war when it is likely to pay. Under these conditions, initiators will win their wars most of the time. The higher the win rate, the more rational the decision making processes. Information is more complete, and calculations are better.

We assume that miscalculation and misperception dominate the process if a state fails to achieve its goals. By definition and assumption, it follows that if a state chooses war for Clausewitzian goals and loses, it has miscalculated and misperceived. The lower the initiator win rate, the higher the overall extent of miscalculation and misperception in decisions for war.

We view the decision making process in much the same way as rational choice practitioners. States gather information, assess and rank their options by calculating the relative utility of these options, and then pick the best option to maximize utility. However, we then assume preferences for initiators. The assumption that initiators want to win does not lack deductive, scholarly, and common sense support, but it is an assumption. It is a useful assumption because with it, we believe we can judge the overall quality of the decision making process over seventy-nine wars.

There are two main arguments against the key assumption. First, our key assumption may hide anomalies such as ‘lucky’ outcomes in some cases. Wars can be won by miscalculators and lost by wise calculators. Second, it neglects the possibility that initiating states could rationally calculate that loss in war would still achieve goals that would justify the war. It may be that winning is not everything. In these cases, loss is not a result of miscalculation and misperception. We address these arguments in turn.

By strict definition, luck means outcomes are random. In practice, luck means that there may be wars whose outcomes hinged on minor factors, or factors outside the control or reasonable ability to predict of the warring states. Luck may explain some war outcomes, and we readily acknowledge that our key assumption likely does not apply to all cases. But there is no reason to believe that luck would generally favor initiators over defenders or vice versa. It would be especially illogical to blame a decline in initiator luck for the decline in initiator in win rates over time, especially when the change is so dramatic and unambiguous. As social scientists, we would much rather argue that miscalculation and misperception have increased over time than that war initiators are increasingly unlucky. If something is systematically reducing the odds in war that something is not luck.

The second critique is that initiators may still profit from loss, and that initiators may rationally start wars without intending to win. This point likely accounts for some wars as well. For example, many argue that Egypt’s Anwar Sadat launched the 1973 Yom Kippur War knowing that he could not win militarily. Regardless of the war’s anticipated limited or losing military outcome, Sadat hoped to regain territories (and pride) lost in 1967 by using the war politically to generate enough international pressure to successfully bargain for the territories (Jordan 1997; Herzog 1975, 27, 37; Rabinovich 2004, 26; Schiff 1974 6-7).

A broader version of this critique is that the definition of Clausewitzian rationality is too limiting. Instead of starting wars to increase a state’s security or wealth, leaders may start wars for a number of reasons that are rational for other purposes. For example, leaders may start scapegoat wars to focus the attention of domestic constituents on external issues and rally the nation around the flag. In scapegoat wars, keeping the leader in power may be more important than victory. Some wars may be explained by the machinations of a military-industrial complex that needs a fight from time to time to further its organizational goals. Perhaps leaders or societies periodically need wars to prove their self-worth for reasons lying in personal insecurities or in pathological group psychology such as social-Darwinism. A state may prefer to fight and lose than to back down for reasons of pride or credibility.

This second critique might be made most directly by rational choice practitioners. “The rationality assumption tells us nothing about how actors form their preferences, but rather shows how actors behave, given their preferences,” notes Bueno de Mesquita (1981, 31). Similarly, Morrow writes: “rationality tell us nothing about an actor’s preferences over outcomes – only about its choices given those preferences and the situation that confronts it.” 1994, 21; see also Lake and Powell 1999).

Thus, there are many possible reasons why even a losing war may serve some goal of the initiator. Yet would not victory usually do more than loss to further domestic political, organizational, psychological, or credibility goals? Would not a leader’s domestic position be more bolstered from victory than loss? In the 1973 War example, Sadat would have preferred to win back the territories from Israel through victory, not gambit, had it been possible. Even if initiators are not pursuing power, security, and wealth for their state (which Sadat was), victory is probably better for their goals than loss. Deductively, the safest argument remains that states and leaders generally start wars hoping to win, and that loss therefore represents miscalculation and misperception.

In addition to these arguments that hopefully rebut some critiques of our assumptions, we draw support from a number of rationalist authors and schools which implicitly or explicitly agree that states start wars planning to win them. Core assumptions of realism are that states are concerned about relative power because they live in a self-help, zero-sum world. States have goals ranging from power preservation and survival to power maximization. Given those assumptions and goals, it is impossible to infer that states will generally prefer losing the wars they start. Mearsheimer posits that the “trick” for power maximizing great powers is to figure out when to initiate successful wars (Waltz 1973; Posen 1984; Mearsheimer 2001, 39-40). Allison and Zelikow’s Rational Actor Model assumes that states pursue the strategic goals of “national security and national interests” in the face of external threats and opportunities (Allison and Zelikow 1999, 24). Losing wars can not be a frequent goal in this model either. Allison and Zelikow argue at length that the Rational Actor Model underlies scholarship from classical and structural realism to international institutionalism and expected utility approaches (1999, 26-48).

Schelling begins his rationalist approach to the strategy of conflict by “working with an image of participants who try to ‘win’” (1960, 4). Morrow writes that “War is seen as a struggle to impose military reverses upon the other side” (1985, 476). In Bueno de Mesquita’s The War Trap, the utility of war hinges greatly on the perceived prospects of success in war. (1981, 46-48). In addition, Bueno de Mesquita uses initiator win-rates to justify his expected utility approach to the causes of war. He begins with his finding that initiators won 42 of 58 (72%) interstate wars between 1815 and 1974.^[2] Because initiators win frequently, he wrote: “we can reasonably believe, then, that wars are purposive.” In contrast, “if war is unintentional, we should not expect a systematic relationship between those who start wars and those who win wars” (1981, 20-22). If he was truly agnostic about assuming preferences, any win rate might indicate purposive behavior.

Not only do many rationalists agree with the assumption that initiators want to win, some also assume a fairly rational decision-making process. Almost by definition, this is explicitly true for rational choice practitioners. For them, this rational process is one in which actors gather information, predict outcomes, calculate and rank utilities, and act strategically to “pursue their goals as best they can” (Lake and Powell 1999, 7). According to Morrow, “rational behavior means choosing the best means to gain a predetermined set of ends….actors are trying to create more desired outcomes rather than less desired outcomes” (1994, 17). To the extent that rational choices imply decent information and calculation, these statements imply a decent level of success for rational actors. These practitioners also acknowledge that mistakes may happen, due to incomplete information and other bounds to full rationality. Even after war initiators have made their best calculations, they may sometimes lose.

However, if reasonably good calculators repeatedly lose, those who have some faith in the decision making process must argue that losing wars now has positive utility for many initiators, and/or that other options were worse than the losing war often forecast by these decent calculators. We have yet to discover anyone who argues that initiators increasingly and now generally prefer losing wars to winning them, or that losing wars is increasingly and now generally seen to be the least-worst policy option for initiators. Either would explain a 67% loss rate since 1945.

In the end, the extent to which the declining win-rate reflects an increased preference for losing wars or increased miscalculation and misperception is an empirical matter. Maybe both help explain the decline in win rates. We look forward to trying to explain our findings in more depth as this project continues, and we hesitate to make un-conditioned judgments between the two contending explanations before the facts are in. None of our arguments are aimed at the techniques of formal modelers. Indeed, if miscalculation and misperception have increased, then the willingness of the rational choice approach to look across levels of analysis and to not assume preferences offers a model well-heeded by other approaches. That said, if our assumptions are right, then miscalculation and misperception have become so pervasive in decisions for war that assumptions about even boundedly rational decision making processes in this domain must be recalibrated.

Many of the scholarly and policy implications of this study obtain regardless of whether initiators increasingly find it rational to fight losing wars or are plagued by miscalculation and misperception. Either way, the causes of war are becoming harder to study because it is more difficult to make assumptions about preferences and behavior, and to assess the sources of and influences on preferences and behavior. Either way, the world is becoming more dangerous because it is harder to prevent war through deterrence.

Definitions

Because of our key assumption, outcomes largely define the key concepts in this paper: miscalculation, misperception, and rationality. If a state starts a war and loses, then miscalculation and misperception dominated the decision-making. If a state starts a war and wins, the decision was dominated by rational calculation. Yet for the purposes of transparency and in order to more fully engage debates about rationality and miscalculation and misperception, we briefly define our terms here.

Misperception: There are two types of misperception. The first is when incorrect data is received by the decision-maker. Incorrect data describes a situation in a way that does not correspond with objective reality. The second type of misperception occurs when the decision-maker distorts incoming information. For whatever reason it occurs, imperfect information is misperception. Misperception can cause miscalculation.

Miscalculation: Miscalculation occurs when a decision-maker obtains different results than intended: if he/she pushed button A expecting result X, but instead gets result Y. These definitions mean that even optimal calculation using imperfect information constitutes miscalculation and misperception if it results in unintended consequences. Unintended consequences signify miscalculation (for discussion of this issue, see Fearon 1995; Jervis 1988; Levy 1983).

Rationality: Perfect rationality means making decisions to maximize utility based on perfect information about all available choices and their consequences. If all states and actors were perfectly rational, war would be rare because states could predict outcomes in advance and losers in particular would, presumably, have strong incentives to bargain to prevent war (Fearon 1995; see also Bueno de Mesquita and Lalman 1992). Blainey’s argument that "most wars were likely to end in the defeat of at least one nation which had expected victory" would rarely apply (1973, 144-145) because the future loser would capitulate in advance of the war. Of course, the real world is one of bounded rationality. From opacity in the international system, to limits in human cognition and physical and organizational limits of intelligence services, those obtaining and processing information face many hurdles.

As we acknowledged above, actors will not always get their preferred outcomes because of luck and bounded rationality (Lake and Powell, 1999, 31). Yet it is reasonable to assess the rationality of war by assuming initiators want to win, and asking: “do initiators get their preferred outcomes most of the time?”

A major task for case study researchers is to come up with intersubjectively agreeable coding rules that can place decision-making for war along the continuum from almost perfectly rational, boundedly rational, and very boundedly rational, to decisions dominated by miscalculation and misperception. These coding rules do not exist, which is one reason why scholars talk past each other when arguing about general causes of war, and about causes of specific wars. Contributing to the development of coding rules for miscalculation and misperception is an aspiration of the “Is War Rational?” project, but it is not the focus of this article.

Data and Coding Rules

We used the Correlates of War (COW), Militarized Interstate Dispute (MID), and National Material Capabilities (NMC) databases to code key variables for all of COW’s 79 major interstate wars from 1815 to 1997. The variables we used from these datasets include initiators, targets, joiners of attackers, joiners of targets, war outcomes, duration of war, fatalities, and relative power of all parties to the war. These merged variables form the “Is War Rational?” (IWR) database, and are needed for our major tasks: determining win/loss rates for initiators, and examining whether relative power (including coalitions and joiners) influences and helps predict outcomes. We have not recoded any aspects of these three databases.

The COW dataset focuses on serious military conflicts (defined as having 1000 or more battle deaths) between states from 1816-1991. It starts with the Franco-Spanish War of 1823 and ends with the Gulf War of 1990/1991. The MID dataset codes variables in “all instances when one state threatened, displayed, or used force against another from 1816-2001” (Correlates of War home page at: <<http://cow2.la.psu.edu/>>, accessed 1/06/05). The NMC uses six indicators -- military expenditure, military personnel, energy consumption, iron and steel production, urban population, and total population -- as the basis for its Composite Indicator of National Capability (CINC) score, coded by year from 1816-2001. All datasets and some of their coding information are available via the COW home page.

The chief difficulty with the data was figuring out who started each war. Three contenders offered plausible codings for us to determine “Is War Rational?” Initiators: COW Initiator, MID Initiator, and MID Revisionist. Each uses different coding rules. In COW, the Initiator is the side that “made the first attack in strength” (Singer and Small 1972, 366). In MID, the Initiator (or “attacking originator,” in strict MID language) is “the state that takes the first militarized action.” And the MID Revisionist is “the state or states that sought to overturn the status quo ante” (Jones, Bremer, and Singer, 1996, 178; see also Bennett and Stam 2003, 49-51).

Because of these different coding rules, the databases often disagree about who initiated a given war. There are 22 wars where COW Initiator and MID Initiator do not match. There are 17 wars where there is no overlap between the MID Revisionist and the COW Initiator (ie. no MID Revisionist is a COW Initiator). There are 18 wars where the MID Revisionist is not the MID Initiator. And there are 9 wars in which both sides of the conflict are deemed Revisionist by MID. To illustrate the types of difficulties posed, the MID Initiator for World War II is Poland. Though one has to credit MID for sticking to its coding rules, Poland did not start World War II. Germany is the COW Initiator and the MID Revisionist.

So which of these three possible codings – COW Initiator, MID Initiator, or MID Revisionistare best to use for the IWR Initiator? For the purposes of answering the “Is War Rational?” question, we primarily use the MID Revisionist coding to code the IWR Initiators. The reason is that revisionists aim to change the status quo, while MID Initiator and COW Initiator only indicate which state/s first used force. MID Revisionist best indicates the state/s that is most decisively making the choice for war. However, when both sides are revisionist in MID, we use COW Initiator to break the tie and decide which side is the IWR Initiator. This is because the COW Initiator is likely to have taken a more serious action than the MID Initiator, as the Poland example illustrates.

For the other main variable, outcome, the IWR data includes both COW and MID outcomes. We take the IWR Initiator/s, and see if COW and MID reported these state/s to be the winners, losers, or Tie/Other (see next paragraph). We then report these results as coded by each database, or we average the results. Therefore, we do not need to choose between COW and MID when their outcome coding varies. For example, COW codes clear winners in 48 of the 79 wars, while MID’s total is 39. Thus, we report that states win between 61% (COW) and 49% (MID) of the time, and/or we report the average of 55%.

In the three cases where MID codes a war as “Yield by Side A” (Side A is the attacker in MID), we code this as a loss for initiators because they capitulated to their targets and failed to achieve their goals. “Yield by Side A” outcomes are treated differently from Stalemate, Compromise, and Unclear outcomes in MID because only “Yield” involves clear submission by the initiators. We code the Stalemate, Compromise, and Unclear outcomes in MID as “Other” in the relevant tables, and consider them comparable to the Tie coding in COW. For more discussion of coding outcomes, see Stam (1996), Maoz (1983), and Bueno de Mesquita (1981), as well as the technical appendix to this paper.

The NMC database’s Composite Index of National Capabilities (CINC) score provides yearly estimates of each state’s capabilities relative to other states in the international system for a given year. Six indicators—military expenditure, military personnel, energy consumption, iron and steel production, urban population, and total population are combined to serve as the basis for the CINC. We used COW to indicate the dates during which states were involved in wars. The NMC documentation (2004) makes clear that power is often hard to code. For example, in 32 out of 79 wars, military expenditure or military personnel data for either the initiators or targets do not exist.

After sorting through these issues, a sensitivity analysis (shown below in Table 3) shows that our main findings are robust and conservative..

Findings

Initiator Success Rates

Table 2: War Outcomes for Initiators
	n	% of all wars		n	% of all wars		% of all wars
COW			MID			Average COW/MID
Win	48	61%	Win	39	49%	Win	55%
Lose	24	30%	Lose	24	30%	Lose	30%
Tie	7	9%	Stalemate	11	14%	Tie/Other	11%
			Compromise	1	1%
			Unclear	4	5%
n	79		n	79

As explained above, determining whether initiators tend to win or lose wars is crucial for understanding whether decisions for war are rational. Based on our dataset of 79 major wars dating back to 1815, Table 2 shows that initiators have won between 61% (COW) and 49% (MID) of all wars they started. This is an average win rate of 55%. In both COW and MID, initiators lost 30% of all wars they started. Initiators tie in 9% of wars in COW and stalemate or achieve other outcomes 20% of the time in MID. Chi square tests show that these results are significant at p<.001 for COW, and at p<.01 for MID. The COW dataset is more aggressive in coding definitive winners, while MID is more cautious (Fortna 2004, footnote 44).

How do we know if winning 61% or 49% of the time means that decisions for war tend to be the result of rational calculations or are dominated by miscalculation and misperception? Thresholds are in the eye of the beholder. To us, a 50% initiator win rate is indeterminate. Given that war is so costly, decisions for war should be well-calculated (Bueno de Mesquita 1981, 32). This increases the extent to which 50% seems like miscalculation. On the other hand, maybe defensive advantages make this a good win rate (though wise initiators would take this into account). As the percentages diverge from 50%, conclusions are easier to draw. A two-thirds win rate implies that decisions for war tend to be well-calculated. A one-third win rate suggests to us that decisions for war are dominated by miscalculation and misperception.

Sensitivity Analysis

A sensitivity analysis shows that our coding rule of using primarily MID Revisionist to determine initiators yields outcomes that are conservative with respect to our core arguments that overall initiator win rates since 1815 are nearing fifty percent and are declining over time. There are six possible permutations of the Initiator/Outcome data formed by the three initiators codings of MID Revisionist, MID Initiator, and COW Initiators, and the two outcome codings of MID and COW. As explained above, we primarily use MID revisionist for the initiator, and we report both COW and MID outcomes, or their average. This covers two of the six combinations. To conduct this analysis, we therefore look at the four remaining permutations formed by COW and MID Initiator, and COW and MID Outcome.

We report an overall initiator win rate of 55%. Only the COW/COW column yields results with higher initiator win rates than those we report. Three other permutations (COW/MID, MID/MID, and MID/COW) show lower initiator win rates.^[3] If we had wanted to cook the books against rationalist causes of war, three other coding permutations would have made the job easier. Instead, we used the most theoretically justifiable coding rules for our project.

Table 3: Sensitivity Analysis
	IWR Results	Other Ways of Determining Initiator Win/Loss Ratios
Initiator Outcome	IWR Initiator and Averaged COW/MID Outcomes	COW Initiator / COW Outcome	MID Initiator / COW Outcome	MID Initiator / MID Outcome	COW Initiator / MID Outcome
W	48 (COW) ; 39 (MID)	49	42	35	39
L	24 (COW); 24 (MID)	23	29	27	23
Tie/Other	7 (COW); 16 (MID)	7	7	16	16
Initiator Win Rate for All Wars
%W	55%	62%	54%	46%	50%
%L	30%	29%	37%	34%	29%
%Tie/Other	15%	9%	9%	20%	21%
N		79	78	79	78
Initiator Win Rates Through 1900, then After
%W Pre-1901	73%	75%	69%	56%	66%
%L Pre-1901	21%	25%	31%	31%	22%
%T/O Pre-1901	7%	0%	0%	13%	13%
%W 1901+	43%	53%	43%	38%	38%
%L 1901+	37%	32%	41%	36%	34%
%T/O 1901+	21%	15%	15%	26%	26%

Another confirming sign is that all four permutations show that win rates are declining markedly over time. Finally, all but one permutation yields win rates below the 72% reported by Bueno de Mesquita and the 74% and 67% reported by Wang and Ray for the 1800s and 1900s, respectively (cited above). The exception is the COW Initiator/COW Outcome permutation which yields a 75% win rate during the 1800s.

Initiator Success Rates Over Time

Table 4: Initiator Outcomes by Time Period
	1815-1900	%	1901-1991	%	1946-1991	%
COW
W	25	78%	23	49%	8	35%
L	7	22%	17	36%	9	39%
T	0	0%	7	15%	6	26%
MID
W	22	69%	17	36%	7	30%
L	6	19%	18	38%	9	39%
Other	4	13%	12	26%	7	30%
Avg COW/MID
W		73%		43%		33%
L		20%		37%		39%
Other		6%		20%		28%
n (% of 79)	32	41%	47	59%	23	29%

Overall win rates are a good place to start assessing the rationality of war, but a finer-grained picture is gained by looking at win-rate trends over time. Table 4 shows that in the 32 wars that occurred prior to 1900, initiators won an average of 73% of the time. For the 47 wars after 1900, the success rate dropped to 43%. After 1945, initiators win 33% of the 23 wars. Compared to the win rate through 1900, the odds of success since 1945 have fallen 65%, from 73% to 33%. It was a much better bet for states to go to war in the 19^th century than in the 20^th.

Figure 1 shows the moving average of victory as a percentage of all outcomes. The gap between COW and MID outcomes gives a picture of the historical range or debate between the two. COW provides an upward bound on success rates, and MID a lower bound, but success rates in both decline similarly and significantly.

As initiators win less over time, they lose or tie more frequently. Figures 2 and 3 show the moving averages of initiator wins, losses, and ties over time. These graphs show that in both COW and MID, the loss rate stabilizes near 30% in the mid-1900s. Despite this, MID’s win rate is less than COW’s. The reason for this gap lies in the amount of wars coded as ties in COW and “other” outcomes in MID. MID shows the rate of tying/other outcomes declining to around 10% in 1920, but then rising back up towards 20% in modern times. In COW, no ties occur in the first one hundred. The first tie is in 1920, and ties as a percentage of all outcomes rose to about 10% since. With this 10% increase in ties as a percentage of all outcomes, COW and MID appear to be moving hand in hand since 1920.

In her ongoing study on the increasing rate of tying, Fortna argues: “If draws have become more prevalent, perhaps war is becoming less effective as a decision mechanism” (2004, 5-6). She considers factors that might have caused the increase in ambiguous outcomes, including the combatants’ ability to win decisively, their ability to cease fighting, and the possibility that war coding is flawed for recent outcomes since we do not yet have a long-terms lens for these wars. However, Fortna does not directly answer the “Is War Rational?” question. If one assumes that initiators do not start wars in order to draw, the fact that they are increasingly unable to win outright suggests that pre-war decisions were rooted in misperception and/or miscalculation.

The Impact of Capabilities on Outcome

The most obvious determinant of war outcomes should be relative power. Strong initiators should win wars more frequently. Figure 4 parses outcomes by capabilities. The IWR variable of relative capability for the initiator ( RelCap(I) ) is based on each state’s or coalition’s Composite Indicator of National Capability (CINC) score and it measures the relative capabilities of initiators to targets on the first day of any war. If RelCap(I) = 0.67, then the initiating state(s) have 67% of the power in the conflict, or twice as much as the target side. A change of 0.25 in RELCAP such as that from .375 to .625 means a minimum 2.78 fold increase or decrease in straight capability. The significance of a .25 change increases as one gets away from .5, or parity. For example, a RELCAP change of .25 from .9 to .65 is an almost a five fold change in capability (from having a 9:1 ratio of power to 1.9:1 ratio).

In the 38 wars when initiators are at least three times stronger (RelCap (I) = >.75), they win an average of 62% of the time (the average of 66% of the time in COW and 58% in MID). When the initiator’s relative capability is less than three times as strong, win rates sink to 50% -- or just below for modestly strong initiators.

We parse the data into these quartiles in part to help analyze the “3:1 rule.” This is a common rule of thumb used by strategists is that armies are likely to win in battles (not war outcomes) if they are at least three times more powerful as their targets (Mearsheimer 1989). Looked at here, our data suggests that a three to one power advantage is a fairly useful predictor of war outcomes as well. It is the only category where win rates dominate over losses and ties. Oddly though, initiators who were stronger than their targets but less than three times as strong (0.75>RelCap(I)>0.5), did less well than weaker initiators.

Combining all strong initiators (RelCap(I)>0.5; N=49), the average win rate is 58%. These findings do not overwhelmingly favor power as a predictor of outcomes, and some of our other findings further vitiate power as a predictor, but Maoz’s argument that “capability variables [are] unrelated to dispute outcomes” does not appear to hold (1983, 220).

In future work, we will use this analysis of outcomes and power to help pick cases for further study. Cases where strong initiators lose to weak targets suggest high degrees of miscalculation and misperception. Cases where weak initiators win against strong targets suggest superior calculation. These cases may provide prototypical examples of miscalculation and misperception or rational calculation. We can then use these examples to help develop coding rules for placing cases along the rationality / miscalculation and misperception continuum (see definitions above).

The Impact of Joiners on Outcome

We examine joiners in part to see if they are a source of power, and thus might add predictability to outcomes. In fact, joiners generally seem to be a source of miscalculation and misperception. Most research on joiners focuses on issues such as how alliances may cause or diffuse war by pulling states into the conflict (Christenson and Snyder 1990; Siverson and King 1979), or on predicting when allies will enter a war (Yamamoto and Bremer 1980). Stam argues that alliances influence outcomes, but with diminishing returns (1999, 148-152). Stam does not investigate whether joiner wars favor initiators or targets, or whether joiners are a source of miscalculation and misperception.

Table 5: Joiners vs. Outcome
	Do joiners enter the war?
COW	No	%	Yes	%
W	41	69%	7	37%
L	15	25%	9	47%
T	6	10%	1	5%
MID	No	%	Yes	%
W	32	54%	7	37%
L	18	31%	6	32%
Other	3	5%	4	21%
n	62		17

The IWR database adds a field to code each war as a joiner or non-joiner war, and this also indicates if a war has offensive joiners (joiners on the side of the initiator), defensive joiners (joiners on the side of the target), or both. We also code for coalition wars, to distinguish between wars where there are multiple day one initiators (and/or defenders) and joiners who come into the war after day one. From the point of view of identifying factors that affect the predictability and calculability of war outcomes it is useful to distinguish between joiners and day one coalitions. Presumably, the latter make outcomes easier to predict.

The results of parsing war outcomes by the presence of joiners are displayed in Table 5. This table shows that when joiners enter wars, the initiator success rate falls from an average of 55% (for all wars) to 37%, while initiator the win rate in non-joiner wars rises to 61.5%. Thus, the addition of joiners has a substantial influence on war outcomes.

To estimate how much of the difference in success rates is explained by balancing against initiators, we look at the subcategories of offensive and defensive joiners in Table 6. Only 17 of the 79 (22%) wars involve joiners, so these results are not terribly robust, and additional parsing further reduces the sample sizes.

When only offensive joiners are present, they do not do much to help initiators. The win rate in wars with only offensive joiners is 62% in both COW and MID (N=8). This is a seemingly small increase of 7% over the aggregate average initiator win rates for all wars of 55%. When there are only defensive joiners (N=6), they balance effectively against the initiator and initiators win only 33% in COW and MID. In the rare cases (N=3) when both sides have joiners, the initiator win rate is zero. All wars with defensive joiners (N=9;

Table 6: Joiners by Side vs. Outcome
COW	Offensive Joiners	Defensive Joiners	Both Sides Joiners
W	5	2	0
L	3	4	2
T	0	0	1
MID	Offensive Joiners	Defensive Joiners	Both Sides Joiners
W	5	2	0
L	1	3	2
Other	2	1	1
n	8	6	3

11% of all wars) have an initiator win rate of 22%.

The clearest implication of these findings is that defensive joiners are a source of miscalculation and misperception (Van Evera 1999, 28). Whenever there are defensive joiners, the success rate of initiators declines dramatically. As offensive joiners do not add much to the offense, it may be that they are a source of optimistic miscalculation as well. Initiators may be hoping for more than they get. A second implication is that when balancing occurs, it works. However, with an N of nine for wars with defensive or both offensive and defensive joiners (11% of all 79 wars), balancing against wartime threats is not frequent.

Looking at the presence and effects of joiners over time, in the 1800s, initiators won five of the eight joiner wars (62.5%). Thereafter, initiators won only two out of the nine joiner wars (22%). The declining success rate for initiators in joiner wars may be partly caused by the uptick in wars with any defensive joiners and the decline in wars with offensive-only joiners. Six of the nine wars with any defensive joiners were 1913 or after, but defensive joiner-only wars are evenly split over time. Six of the eleven wars with any offensive joiners were 1913 or after, but five of the eight offensive joiner-only wars were pre-1913.

The Joint Impact of Capabilities and Joiners on War Outcome

Our analysis has so far shown how relative capabilities and the presence of joiners affect the quality of the pre-war bet made by initiators. We now look at how the presence of joiners affects the outcome for initiators of various strengths. Gartner and Siverson (1996, 12) argue that “initiators may win not only because they have capabilities that are superior to those of their targets but also because they are generally successful in calculating whether their targets will receive help.” So far, we have shown that defensive joiners hurt the success rate of initiators and are a source of miscalculation and misperception.

Table 7, below, shows that in non-joiner wars very powerful states win an average of 72% of the time; N=30. When there are joiners, the success rate for the most powerful plummets to 25%; N=8. The Ns are small, but joiners have powerful negative effects against the strongest initiators. These results suggest that powerful initiators may be overconfident in their calculations, or that they spur more effective balancing. Once again, the N of eight is small, but of the eight joiner wars with powerful initiators (the far right column above), only three were limited to offensive-only joiners, of which the initiators won two. This means that five of the eight wars with powerful initiators had defensive joiners and all were losses (or two stalemates in the case of MID) for the initiator.

Table 7: Joint Effects of Joiners and Capabilities on Outcome
Were joiners present in the war?
No					Yes
RelCap(I)	< .25	.25 - .5	.5 - .75	>.75	RelCap(I)	< .25	.25 - .5	.5 - .75	>.75
COW					COW
W	4	9	5	23	W	2	2	1	2
L	3	4	4	4	L	1	1	1	6
Tie	1	2	0	3	Tie	0	1	0	0
MID					MID
W	3	6	3	20	W	2	2	0	2
L	4	5	3	6	L	0	1	2	4
Other	1	4	3	4	Other	1	1	0	2
n	8	15	9	30		3	4	2	8

To the extent that there are only seventeen joiner wars out of seventy-nine wars, Gartner and Siverson may be right. Perhaps initiators do a good job of avoiding joiner wars. On the other hand, when there are joiners, they tend to hurt the success rate of initiators. This is particularly true when the initiators are strong.

To pursue this analysis, we have to further distinguish between true dyadic, coalition, and joiner wars. Coalition wars are when there are multiple states on one or both sides of the conflict on day one. Because they are all involved on day one of the conflict, these are not considered joiner wars, but coalition wars. There are eleven coalition wars in the “No Joiners” sections on the left of Table 7 above, and six in the “Joiners” section on the right. To analyze purely dyadic wars, we moved the 11 coalition wars to the right side.

Coalition wars should represent even firmer alliances than joiner wars, as the allies were all willing to commit on day one. Compared to joiner wars, predictability of outcomes should be easier in coalition wars, and initiator win rates should rise. Likewise, purely dyadic wars should have the highest win rates. This is indeed what we find.

Above we saw that win rates for all joiner wars were 37% (COW and MID average). Adding the coalition wars into the joiner wars yields a total of twenty-eight wars in this category and boosts the success rate for coalition/joiner wars to 46%. Strong initiators in coalition/joiner wars also fare better - win rates go from 25% to 36% over thirteen wars. In the now pure dyadic category, when a single initiator is at least three times more powerful than its single target, initiator win rates go up modestly from 72% (N=30), to 76% (N=25). This shows that true dyadic wars started by strong initiators are the best bets, and that initiators in coalition wars with allies willing to enter the war on day fare better than in joiner wars. In both cases, accurate calculation seems easier, and miscalculation and misperception is reduced.

Should initiators be able to predict the presence of joiners? Recent studies into alliance reliability by Brett Ashley Leeds (2000, 2003) complement this analysis. Previous empirical work (Sabrosky 1980; Siverson and King 1980) concluded that alliance members only came to the aid of their partners 25% of the time; therefore, alliances were generally unreliable. Leeds’ Alliance Treaty Obligation and Provisions (ATOP) dataset shows that alliances are in fact reliable 74.5% of the time. If we evaluated the pre-war cost-benefit calculus of a rational initiator, we would expect to see evidence that decision-makers considered the possibility of third party intervention. Gartner and Siverson (1996, 14) note in their study on war expansion and war outcomes that “when alliances are present, initiators select as targets those states whose alliance partners have been judged, ex ante, by the initiators to be unreliable.” Thus, if most initiators assume alliances to be unreliable, and Leeds is right that they are in fact usually reliable, then this explains one way joiners are a source of misperception and optimistic miscalculation and bring down initiator success rates.

Power and Outcomes Over Time

Another way to look at power and outcomes is to analyze the relative power of winning and losing initiators over time. If, on average, initiators or targets are winning their wars with less power, this would help confirm the argument that outcomes are increasingly divorced from obvious indications of power. Conducting this analysis may also shed light on whether changes in the offense/defense balance help explain the declining win rate for initiators. For example, if declining initiator win rates were due to changes in the offense/defense balance in favor of the defense, possible observable implications are that initiators are losing more despite increasing or constant relative power being brought to bear while winners are doing so with more power being brought to bear. If this were so, something would be making offense harder and defense easier. Likewise, if initiators who win do so with increasingly less power, then that would possibly signal increased offense dominance (Glaser and Kaufmann, 1998, Jervis 1978, Lieber 2000).

Overall, we find that the predictive power of power (as measured by the National Materials Capabilities database) is declining, and in some ways is not a good predictor of outcomes. To the modest extent our data speaks to the issue, changes in the offense/defense balance over time do not appear to explain the decline in initiator win rates.

Figures 5 and 6 show the composite relative power (RELCAP) scores from the NMC database’s Composite Index of National Capabilities (CINC) for winning (N=39) and then losing (N=19) initiators. The figures only show wars where COW and MID agree on outcomes, and this excludes 21 of the 79 wars.

For all wars in which the initiators win, the power ratio is 2.71:1. After 1900, the average drops to 2.06:1 (N=17), but the power ratios for winners are fairly steady through the 1900s as the average after 1945 is 1.95:1 (N=7). For losing initiators, the average power ratio is 1.139:1 for all 19 wars, rising to 1.37:1 from 1901 on (N=14) and to 1.481:1 (N=7). There is some decline in winners’ power, but this decline is not very significant after the moving average stabilizes. The power of initiators who lose appears to be rising, but has been fairly steady since 1914. Together, these findings suggest a very modest decline in the predictive power of power.

When one compares the power ratios of winners to losers, initiating winners tend to have a good deal more power over their adversary than initiating losers. At first, this bolsters the predictive power of power. However, as winners win with less power, and losers lose with more power, this actually reinforces the argument that the predictive power of power is on the wane. These trends also suggest that it is hard to explain the declining win rate on the offense/defense balance. If the defense was getting harder, initiators would need more power to win, not less. If anything, the world has become more offense dominant. This is a puzzle: initiators are winning far less often, but when they do win, they are doing so with somewhat less power over time.

Finally, the standard deviation increases over time for the power of winning initiators, going from around .22 in the late 1800s (when the moving average of the standard deviations stabilizes) to almost .3 in 1990. In contrast, the standard deviation moving average is flat for losing initiators. For winning initiators, this is another sign that the predictive power of power is declining as they win with increasingly less relative power and lose with increasingly great relative power. Trends aside, in both figures, we see wars widely dispersed on either side of the moving averages for relative capabilities.

The harder it is to predict outcomes based on the most obvious predictor of outcomes (relative power), then the more likely it is that miscalculation and misperception dominate decisions for war. However, many of the trends in this section level out to some degree in the 1900s, while the decline in win rates continues steadily throughout the 1900s. Thus, we do not want to overstate the results in this section.

To better measure relative military power alone, we also ran this analysis with a Military Capability (MILCAP) variable, and again with a Military Expenditure per Soldier (E/S) variable to measure relative quality of forces. The MILCAP is based on NMC’s data on military personnel and expenditures and is the average of each state’s proportion of global military expenditures and military manpower for a given year. Expenditures per soldier were calculated from this same data. Because MILCAP data is spotty and problematic, the N of wars covered by MILCAP and expenditures per soldier is 47 out of the original 79. Of the remaining 47, COW and MID agree on initiator victory for only 18. Of these 18, however, the results are similar to the above figures for RELCAP. The average MILCAP and expenditures per soldier for winning initiators are .67 and .59, with standard deviations of .33 and .27, respectively.

Starting Wars Against the Odds

Our most important finding so far is the odds of starting a war and winning have now dipped down to one in three. This is the primary reason why we argue that miscalculation and misperception dominate decisions for war. However, the picture gets even worse when looking at trends in the rate of war initiation because states continue to start wars in the face of worsening odds. This section also shows that even the strongest initiators are caught in the win rate downdraft. Figure 7 shows that strong initiators with three to one or greater relative overall power have been winning less frequently since around the end of WWI (in both COW and MID), even though they still win at a comparatively high rate overall. A decision-maker with a 3:1 or greater advantage in capabilities in 1900 would observe that previous strong initiators had won around 80% (COW and MID averaged) of all wars. To that leader, war might seem a sound decision. Leaders in 1991 would see a much different picture. Since 1900, strong initiators have only won 45% of their wars. Since 1945, they have won only 42%. Although strong initiators are losing or tying in wars more frequently, Figure 8 shows that since about 1900, the percentage of wars they start has remained stable at just under 50%. Moderately weak initiators (0.25<RelCap(I)<0.5) have started wars more often over time. Since about 1910, states below RelCap(I)=.5 have increased their percent of wins relative to all initiator wins, and are doing so at the expense of the moderately strong states whose win rate has declined for about 100 years.

Despite a declining win rate, and a win rate from 1945-on of 42%, strong initiators have been starting wars at the same rate for almost 100 years. Indeed, the general rate of war initiation has remained constant in our data since 1920. The data also suggest that measuring offense and defense dominance is becoming (even) trickier. States with less power are winning more (as a percent of wars won by initiators), and states with more power are losing more.

Capabilities have become a less accurate indicator of victory. This may suggest that false confidence in the predictive power of power is an increasing source of misperception and miscalculation.

Looking more closely at the rate of war initiation in Figure 9, it increased until about 1920, then held roughly steady since. The post-Cold War era created the impression that interstate war almost evaporated as a problem. That may indeed be true because the last war in is the Gulf War of 1990/91, but the overall moving average suggests no decline in the rate of interstate war. If anything, the rate is increasing slightly. From 1815 through 1900, the moving average of the years between war initiation ends at 2.41. By 1991, for all 79 wars, the average had declined to 2.11. For the 49 wars since 1900, the moving average ends at 1.84 years in between large interstate wars. The lower the number, the greater the frequency of war.

Figure 10 reinforces the argument that war initiation rates are increasing slightly while win rates for initiators are declining dramatically. The moving average for chance of war initiation in a given year ends at 47%. The chance of initiators winning is a composite average of COW and MID win rate moving averages. For all wars, the average ends at 55%. Since 1900, the average ends at 43%. And since 1945, the average ends at 33%.

Influences on the Duration and Deadliness of Wars

When optimistic miscalculation helps cause war, states go into war thinking they will win, and that the war will be quick and relatively easy (Blainey 1973, Van Evera 1999). We confirm that when states calculate well and win, wars are indeed shorter and incur fewer fatalities than when they miscalculate and lose. When initiators lose, the wars are between 27% (COW) and 61% (MID) longer than when they win. For some reason, ties are the longest wars in COW, but other outcomes are the shortest wars in MID.

The presence of joiners also affects the duration of war. Non-joiner wars (where initiators are more successful) average 321 days. On the other hand, joiner wars average 831 days in length, and increase of 259%. This supports claims by Blainey (1973), Wang and Ray (1994, 142), and Bueno de Mesquita (1981) that wars with third party intervention are likely to be longer than wars involving only the initiator and the target.

Looking at fatalities, when initiators lose, they suffer between 4.1 (COW) and 3.3 (MID) times more casualties than when they win. Joiners make things even worse for the attacker but only when they lose. Despite these pronounced average results, the standard deviations are large and there are wide ranges across the wars. Overall, initiators incur fatalities at about two-thirds the rate of targets (.64, with Ns of 12,241,468 and 19,160,076 respectively). If one excludes the World Wars (which comprise 74% of the initiator deaths and 83% of the target deaths out of the 79 wars), the figure achieves parity (.97, with Ns of 3,218,268 and 3,328,562, respectively). This is something of a surprise, as defense is often thought of as advantageous for the defender. Although we are looking at wars, not battles, this suggests a twist on the 3:1 rule of thumb mentioned above. When initiators win, they do not need a 3:1 advantage (because they are incurring casualties at near parity), but when they lose they will incur casualties at a 3:1 or greater rate.

Conclusion

"Well I would say, sir, that there was something dreadfully wrong somewhere"

Lieutenant-Colonel Lionel Mandrake to war-initiating General Jack D. Ripper

in “Dr. Strangelove” (1964)

Findings

The success rate for war initiators is 55% for all major interstate wars from 1815 through 1991. The success rate has declined to one-third in modern wars since 1945. States continue to initiate wars at a fairly constant rate: almost one major interstate every two years since 1920. These findings mean that states are increasingly miscalculating and misperceiving their ways into war, and they are not learning that war increasingly does not pay.

Historically, the strongest states tend to win the wars they initiate, especially when the wars are kept dyadic. In true dyadic wars, war is a good bet and strong initiators with 76% of the time. Although these findings suggest that power is a good predictor of outcomes, other findings mitigate against this conclusion. The win rate for even strong initiators has dropped to 42% since 1945. Strong states often lose wars and weak states win a fair amount the time. Joiners make the overall success rate fall by about one-half to one-third. The effect of joiners is greatest against the strongest initiators, who only win two of the eight joiner wars in this category. In sum, power is becoming a less useful predictor over time.

Joiner wars were good for initiators in the 1800s, but they are increasingly bad. Joiner wars are now, on average, losses for initiators. Joiner wars are not frequent. Out of 79 wars, 17 have joiners, and only 9 have defensive joiners. This is not the robustly balancing world of defensive realists (Walt, 1997). Because joiner wars have lower overall win rates than non-joiner wars, we argue that they are a source of miscalculation and misperception, at least in the 1900s.

Together, these findings suggest that the determinants of war outcomes are becoming increasingly elusive. Relative power should be the best predictor of war outcomes. If it is not, then outcomes must be attributed to harder to measure and less calculable variables such as will or strategy. It makes sense that we find both that miscalculation and misperception is increasing, and that power is an increasingly unsatisfying predictor of war outcomes, albeit at a modest rate.

Implications

What do our findings mean for the study of war, strategic policies, and the future of war? If miscalculation and misperception dominate decisions for war, then more study of miscalculation and misperception is called for. There are two priorities. First, scholars have to learn to better identify miscalculation and misperception in case studies and develop coding rules so that it is easier to agree on the phenomena being observed. Over time, this will also help large-N studies to produce more fine-grained analyses of miscalculation and misperception.

Second, scholars must figure out what it is about modern warfare and statecraft that is causing initiators to misperceive and/or miscalculate more often. Answers may lie in increased balancing, increased defense dominance, increased nationalism, increased pain-tolerance in defenders, variations in transparency, and changes in the political and economic organizations of states. As the “Is War Rational?” project progresses, we hope to test some of these propositions. In general, the large-N community should focus more on outcomes, while all empiricists have to fine-tune the study of less tangible, non-material variables of war outcomes such as willpower, strategy, and nationalism.

To the extent that rationalist and expected utility approaches to the study of war assume that war is a boundedly rational policy choice resulting from reasonably rational policy processes and with a reasonably high expected utility, these approaches are undermined as the initiator win rate falls below 50%. In the face of a recent initiator win rate of 33%, the world seems to have become a place where rationality has gone from bounded to rare, where information has gone from incomplete to poor, where some uncertainty has become mostly ignorance, and where maximizing utility through war has minimal odds of success. We believe that miscalculation and misperception now dominate the foreign policy process in decisions for war.

Turning to policy implications, deterrence should be getting easier. As the utility of war declines, so should its frequency. In fact, deterrence is getting harder. We argue that the general level of miscalculation and misperception is increasing, and, to a modest extent, that outcomes increasingly depend on elusive variables. They are related, and both are bad for deterrence. Moreover, states continue to start wars despite decreasing odds. So we are not just seeing a rise in general miscalculation and misperception, because that could lead to uncertainty, caution, and fewer wars. Instead, we are seeing increased optimistic miscalculation. The odds get worse, yet the bettors keep coming to the casino of war.

We cannot speak to individual cases such as North Korea or Iran, and we do not want to overstate the specific policy implications of our general findings. However, these findings do appear to support policies which rely on arms control and defense and denial, rather than pain-based deterrence. Although defense and denial can aid deterrence, initiators are increasingly either choosing the pain of losing wars, or miscalculating and misperceiving their way into thinking that the pain of loss will not happen to them. In looking at the proliferation of missiles, for example, the Missile Control Technology Regime and other arms control efforts should be pursued with vigor. The benefits of reliable missile defenses also increase as miscalculation and misperception increase.

The most important policy implication is to make policy makers more aware that the policy process is, for whatever reason/s, increasingly flawed. Decisions for war deserve greater scrutiny and caution. The win rate for wars by initiators with 3:1 or greater power has declined to 42% since 1945, while the win rate for all modern initiators has fallen even lower to 33%. The greatest miscalculation and misperception of all is that war is a good bet. This is false optimism. War is now a bad bet.

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COW

MID

War Name

YrBeg

MID rev

COW init

MID init

IWR init

IWR Target

IWR Off. Joiners

IWR Def. Joiners

COW Outcome

MID Outcome

1

89

Franco-Spanish

1823

FRN

FRN

FRN

FRN

SPN

Y

Y

4

189

Russo-Turkish

1828

USR

USR

USR

USR

TUR

Y

Y

7

1552

Mexican-American

1846

USA

USA

USA

USA

MEX

Y

Y

10

19

Austro-Sardinian

1848

ITA

ITA

AUH

ITA

AUH

MOD, TUS

N

Stalemate

13

375

First Schleswig-Holstein

1848

GMY

GMY

GMY

GMY

DEN

Y

Compromise

16

175

Roman Republic

1849

AUH, FRN, SIC

FRN

AUH

AUH, SIC

PAP

FRN

Y

Y

19

1528

La Plata

1851

ARG

BRA

BRA

ARG

BRA

N

N

22

57

Crimean

1853

USR

TUR

USR

USR

TUR

FRN, ITA, UKG

N

N

25

8

Anglo-Persian

1856

UKG

UKG

UKG

UKG

IRN

Y

Y

28

115

Italian Unification

1859

ITA

AUH

AUH

ITA

AUH

FRN

Y

Y

31

1580

Spanish-Moroccan

1859

SPN

SPN

SPN

SPN

MOR

Y

Y

34

112

Italo-Roman

1860

ITA

ITA

ITA

ITA

PAP

Y

Y

37

113

Italo-Sicilian

1860

ITA

ITA

ITA

ITA

SIC

Y

Y

40

135

Franco-Mexican

1862

FRN, SPN, UKG

FRN

FRN, SPN, UKG

FRN

MEX

N

N

43

1519

Ecuadorian-Columbian

1863

COL

COL

COL

COL

ECU

Y

Y

46

194

Second Schleswig-Holstein

1864

GMY

GMY

GMY

AUH, GMY

DEN

Y

Unclear

49

1590

Lopez

1864

ARG, BRA

PAR

PAR

BRA

PAR

ARG

Y

Y

52

1482

Spanish-Chilean

1865

SPN

SPN

SPN

SPN

CHL

PER

N

Stalemate

55

261

Seven Weeks

1866

GMY

GMY

AUH

GMY, MEC

AUH, BAD, BAV, HAN, HSE, HSG, SAX, WRT

ITA

Y

Y

58

88

Franco-Prussian

1870

GMY

FRN

FRN

BAD, BAV, GMY, WRT

FRN

Y

Y

60

1533

First Central American

1876

GUA

GUA

GUA

GUA

SAL

Y

Y

61

187

Russo-Turkish

1877

USR

USR

USR

USR

TUR

Y

Y

64

1518

Pacific

1879

BOL, CHL, PER

CHL

CHL

CHL

BOL

PER

Y

Y

65

3725

Anglo-Egyptian

1882

FRN, UKG

UKG

FRN, UKG

UKG

EGY

Y

Y

67

202

Sino-French

1884

FRN

FRN

CHN

FRN

CHN

Y

Y

70

1535

Second Central American

1885

GUA

GUA

GUA

GUA

SAL

N

N

72

196

Franco-Thai

1893

FRN

FRN

FRN

FRN

THI

Y

Y

73

1490

Sino-Japanese

1894

JPN

JPN

JPN

JPN

CHN

Y

Y

COW

MID

War Name

YrBeg

MID rev

COW init

MID init

IWR init

IWR Target

IWR Off. Joiners

IWR Def. Joiners

COW Outcome

MID Outcome

76

1569

Greco-Turkish

1897

GRC

GRC

GRC

GRC

TUR

N

N

79

1557

Spanish-American

1898

USA

USA

USA

USA

SPN

Y

Y

82

31

Boxer Rebellion

1900

JPN, UKG, USR

FRN, JPN, UKG, USA, USR

AUH, FRN, GMY, ITA, JPN, UKG, USA, USR

FRN, JPN, UKG, USA, USR

CHN

Y

Y

83

3250

Sino-Russian

1900

USR

USR

USR

USR

CHN

Y

N

85

180

Russo-Japanese

1904

USR

JPN

USR

USR

JPN

N

N

88

1205

Third Central American

1906

GUA, SAL

GUA

GUA

GUA

HON, SAL

Y

Stalemate

91

1202

Fourth Central American

1907

NIC

HON

NIC

HON, SAL

Y

Y

94

1086

Spanish-Moroccan

1909

SPN

SPN

SPN

SPN

MOR

Y

Y

97

114

Italo-Turkish

1911

TUR

ITA

ITA

TUR

ITA

N

N

100

1250

First Balkan

1912

BUL, GRC, YUG

YUG

BUL

BUL, GRC, YUG

TUR

Y

Y

103

1251

Second Balkan

1913

GRC, RUM, TUR, YUG

BUL

BUL

GRC, YUG

BUL

RUM, TUR

Y

Y

106

257

World War I

1914

AUH

AUH

AUH

AUH

YUG

BUL, GMY, TUR

BEL, FRN, GRC, ITA, JPN, JPN, POR, RUM, UKG, USA, USR

N

N

109

1219

Russo-Polish

1919

POL, USR

USR

USR

USR

POL

N

N

112

1265

Hungarian-Allies

1919

CZE, FRN, RUM, UKG, YUG

CZE, RUM

FRN, ITA, UKG

CZE, RUM

HUN

Y

Y

115

1270

Greco-Turkish

1919

GRC

GRC

GRC

GRC

TUR

N

N

116

3134

Franco-Turkish

1919

FRN

FRN

FRN

FRN

TUR

Tie

N

117

1272

Lithuanian-Polish

1920

POL

POL

POL

POL

LIT

Y

Y

118

41

Sino-Soviet

1929

USR

CHN

USR

CHN

Y

Unclear

121

129

Manchurian

1931

JPN

JPN

JPN

JPN

CHN

Y

Y

124

1027

Chaco

1932

BOL, PAR

PAR

PAR

PAR

BOL

Y

Y

125

1129

Saudi-Yemeni

1934

SAU, YAR

SAU

SAU

SAU

YAR

Y

Unclear

127

111

Italo-Ethiopian

1935

ITA

ITA

ETH

ITA

ETH

Y

N

130

157

Sino-Japanese

1937

JPN

JPN

JPN

JPN

CHN

Y

Unclear

133

184

Changkufeng

1938

JPN, USR

USR

USR

USR

JPN

N

Stalemate

136

183

Nomonhan

1939

JPN, MON, USR

JPN

MON

JPN

MON, USR

N

N

139

258

World War II

1939

GMY, ITA, JPN

GMY

POL

GMY

POL

BUL, FIN, FRN, HUN, ITA, JPN, RUM

AUL, BEL, BRA, BUL, CAN, CHN, ETH, FRN, GRC, ITA, MON, NEW, NOR, NTH, RUM, SAF, UKG, USA, USR, YUG

N

N

142

179

Russo-Finnish

1939

USR

USR

USR

USR

FIN

Y

Y

145

613

Franco-Thai

1940

THI

THI

THI

THI

FRN

Y

Y

147

1238

First Kashmir

1948

PAK

IND

IND

PAK

IND

Tie

N

COW

MID

War Name

YrBeg

MID rev

COW init

MID init

IWR init

IWR Target

IWR Off. Joiners

IWR Def. Joiners

COW Outcome

MID Outcome

148

1793

Palestine

1948

EGY, IRQ, JOR, LEB, SYR

EGY, IRQ, JOR, LEB, SYR

EGY, IRQ, JOR, LEB, SYR

EGY, IRQ, JOR, LEB, SYR

ISR

N

N

151

51

Korean

1950

PRK, ROK

PRK

PRK

PRK

ROK

CHN

AUL, BEL, CAN, COL, ETH, FRN, GRC, NTH, PHI, THI, TUR, UKG, USA

Tie

Stalemate

154

606

Russo-Hungarian

1956

USR

USR

USR

USR

HUN

Y

Y

157

200

Sinai

1956

EGY

ISR

EGY

EGY

ISR

FRN, UKG

N

N

160

199

Assam

1962

CHN, IND

CHN

IND

CHN

IND

Y

Y

163

611

Vietnamese

1965

DRV

USA

USA

DRV

AUL, RVN, USA

CAM, PHI, ROK, THI

Y

Y

166

1312

Second Kashmir

1965

PAK

IND

PAK

PAK

IND

Y

Stalemate

169

1035

Six Day

1967

EGY, JOR, SYR

ISR

SYR

EGY, JOR, SYR

ISR

N

N

172

1480

Israeli-Egyptian

1969

EGY

EGY

ISR

EGY

ISR

Tie

Stalemate

175

1206

Football

1969

HON

SAL

SAL

HON

SAL

N

Stalemate

178

1447

Bangladesh

1971

IND

IND

PAK

IND

PAK

Y

Y

181

1046

Yom Kippur

1973

EGY, SYR

EGY, SYR

SYR

EGY, IRQ, SYR

ISR

JOR, SAU

N

Stalemate

184

1293

Turco-Cypriot

1974

TUR

TUR

TUR

TUR

CYP

Y

Y

187

1435

Vietnamese-Cambodian

1975

DRV

DRV

DRV

DRV

CAM

Y

Y

189

2069

Ethiopian-Somalian

1977

SOM

SOM

SOM

SOM

CUB, ETH

N

N

190

2141

Ugandan-Tanzanian

1978

UGA

UGA

UGA

LIB, UGA

TAZ

N

N

193

3007

Sino-Vietnamese

1979

CHN

CHN

CHN

CHN

DRV

Y

Y

199

2115

Iran-Iraq

1980

IRQ

IRQ

IRQ

IRQ

IRN

Tie

N

202

3077

Falklands

1982

ARG

ARG

UKG

ARG

UKG

N

N

205

3442

Israel-Syria (Lebanon)

1982

SYR

ISR

SYR

SYR

ISR

Tie

Stalemate

208

3638

Sino-Vietnamese

1987

CHN

CHN

DRV

CHN

DRV

Tie

Stalemate

211

3957

Gulf War

1990

IRQ

IRQ

IRQ

IRQ

KUW

CAN, EGY, FRN, ITA, MOR, OMA, QAT, SAU, SYR, UAE, UKG, USA

N

N

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¹ Contact information: Dan Lindley, Assistant Professor, Department of Political Science, 448 Decio Hall, University of Notre Dame, Notre Dame, IN 46556. Phone: 574-631-3226; Fax: 574-631-8209; Email: dlindley@nd.edu; Webpage: http://www.nd.edu/~dlindley/; Ryan Schildkraut, student, University of Minnesota Law School, Walter F. Mondale Hall, 229 19th Avenue South, Minneapolis, MN 55455, 612-702-4907, schil131@umn.edu. Contact Dan Lindley for correspondence regarding this article. Comments welcome. All data and a technical appendix are available on request or via the dlindley webpage above. Key methodological points are summarized in the text, but for the purpose of journal review, the technical appendix is included. The appendix is not necessary for understanding the article. Rev. 2.0, 2/9/2005, word count: 13,681.

Our thanks to David Campbell, Emma Cohen de Lara, Katherine Jeter, Lauren Kimaid, Garrick Merlo, Adam Shanko, Mariana Sousa, James Thompson, Stephen Van Evera, Paul Vasquez, Jennifer Wiemer as well as to numerous panel discussants and other commenters at conferences. The University of Notre Dame Laboratory for Social Research and the Office of Faculty Research also supported this project.

^[1] Cites for some of these theories or schools are in the bibliography, but there is not room for full cites for every entry. See Levy 1989 for a comprehensive overview of causes of war.

^[2] According to our data, the initiator win rate through Bueno de Mesquita’s cutoff of 1974 was 58.5% (Our N is 69 wars with win rates of 65% in COW and 52% in MID). This may be due to changes in COW data and coding, and/or to Bueno de Mesquita’s recodings (1981, 99-100), and/or to our use of MID Revisionist as the main source for initiator coding.

^[3] To explain why the Ns are 78 in two columns, the COW and IWR initiators of Czechoslovakia and Rumania initiate (and win) a war against Hungary in the 1919War of the Hungarian Allies (COW war #112). But in MID, the initiators are France, Italy, and the United Kingdom, and they are not participants in COW or IWR. Hence, there is no way to make COW and MID Initiators and Outcomes speak to each other.