I will make two main arguments in this article. First, that most wars have been irrational in terms of means or ends, and often of both together. As Benjamin Franklin remarked, “There never was a good war or a bad peace.” Second, that the perpetrators of irrationality have almost invariably been rulers and their entourages. I draw for these propositions from the quantitative research by political scientists on wars since 1816, but mostly from my own sample of long-run sequences of war across history, relying on the research of historians, on the Roman Republic, ancient and imperial China, Japan from feudalism to 1945, Europe over a millennium until today, pre- and post-colonial Latin America, and the United States from the Civil War to today. This enables me to put individual wars into their historical and environmental contexts. Rather than referencing a mass of sources here, I present my bare conclusions. Evidence and sources are available in my recent work, On Wars, published by Yale University Press in 2023.
There are different kinds of war. I distinguish offensive from defensive wars and from middling categories of mutual provocation and escalation. I focus most on wars of offense (or aggression) and divide them into four main types: in-and-out raiding; intervention to change or reinforce a regime abroad (informal imperialism); war to seize slivers of border territory; and territorial conquest followed by direct imperial rule. All four have their own peculiarities.
War is not universal, but it is ubiquitous, occurring in all regions of the world and all periods of history, if in very varying amounts. Yet years of peace have everywhere far outnumbered those of war. Most interstate conflicts have been settled by negotiation and conciliation or continue to fester amid mutual grumbling. But peace has always been considered less noteworthy than war, as evidenced by early inscriptions, chronicles, and sagas to today’s mass media. Wars are exciting. They sell better than peace. They get publicized.
War is not genetically hard-wired into humans nor is it hard-wired only into men. True, men have caused and fought virtually all wars, but because of their culture and institutions, not their genes, and recent armies and especially guerrilla forces have included many women. For over 90 percent of their time on earth, humans probably fought almost no wars, but when fixed settlements generated states, social classes, and literacy organized war became ubiquitous. Thus societies and their leaders, not universal human nature, cause wars. My data show no long-term trend toward either more or less war, provided we add together inter-state, civil, and extra-state wars and note the increasing civilian casualties, arms sales, and internationalization of modern civil wars. Yet military power is only one of four ways for humans to acquire whatever material or ideal resources they may desire. So the question becomes, why do they sometimes use military power rather than rely on cooperative norms, economic exchange, or political diplomacy to attain their goals?
Realism
The dominant theory of war and peace has been political science Realism, with its three major concepts: anarchy, hegemony, and rationality. Anarchy contrasts the rule of law within states with its absence abroad. Thus, rulers are always anxious about other rulers’ intentions, often fearing for their own survival amid normless international anarchy. This entails “security dilemmas,” as both sides take steps to increase their security which alarms the other, into increasing this too, potentially escalating into war. This is the most powerful Realist argument.
Yet Realism neglects domestic causes of war and peace. Eckstein [Reference Eckstein2006], for example, sought to explain the Roman Republic’s wars almost entirely in terms of geopolitical anarchy. This made some sense for the early wars of the republic, but domestic power relations became much more important later on. Most Roman wars were wars of aggression, leading to conquest of peoples who did not threaten Roman survival. Instead, the main driver of war was the militarism which had become pervasive in Rome’s economic, ideological, and political institutions and culture.
To this we can add the main contribution made by Marxists to the study of early wars. In class-divided societies, ruling classes had to extract by force the surplus created by peasants who were in actual possession of the land, in order to finance their privileged existence. Wars cannot be separated from the nature of the societies committing them, including but not only class relations.
Realism also downplays culture and norms. Liberal theorists focus more on peace which they correctly say has virtues of its own. They also emphasize shared pacific norms advocated by agencies like Confucianism, some religions, and the United Nations. Some shared norms do restrain or at least regulate wars, as in the treatment of prisoners of war or civilians. These norms regularly fray, but often they are respected. However, shared norms also include warrior virtues that favor war, as in the feudalisms of China, Japan, and Europe or in modern fascism. Norms may lead to either war or peace–but they are important.
The opposite of anarchy in Realism is hegemony: peace will follow if a single state has military power and the legitimate authority to regulate geopolitics. In many world regions one great imperial state emerged out of a plethora of small ones to regulate their relations with each other and provide social order. Yet this achievement involved countless lives lost in war, and most imperial states actually continued to make war against new enemies until their fall, usually in war. Hegemony is no guarantee of peace. It has also varied regionally within empires. Imperial China’s relatively peaceful tributary diplomacy with states to its southeast contrasted with its warlike relations in other regions. The American empire since 1945 generated hegemonic peace in Western Europe; it moved toward hegemony after decades of wars in East Asia, but this was not achieved in the Middle East or Latin America. Hegemony may sometimes reduce war but sometimes not, and it is too rare to be the main cause of peace.
Finally, Realists say war and peace decisions hinge on rational choice of means and ends. Defensive Realists say states prioritize survival and calculate rationally the means of ensuring this. Aggressive Realists say that states calculate the economic or strategic profit from war set against its cost in treasure and lives and the likelihood of military victory. If the odds seem favorable, states will go to war. States will initiate war when militarily strong and choose defense or diplomacy when weak. I will focus on these propositions and cast considerable doubt upon them.
Rationality and Aggressive War
Rulers themselves believe their decisions for war are rational in terms of both means and ends, and they will surely try to avoid a war they believe they are likely to lose. So I first pose a simple question: Do those who initiate aggressive wars win them? Obviously some do not, but that may only indicate understandable mistakes. What if initiators systematically lost wars or fought costly wars with no victor? Quantitative data are available for wars since 1816, and I can add earlier historical cases.
Small and Singer [Reference Small and Singer1970] found that between 1816 and 1965 initiators were victorious in 34 of 49 wars, suggesting relatively rational decision making. Yet in 19 of these cases, the initiator was a major power attacking a minor power. Of these, the major power initiated hostilities on 18 occasions and won 17. This is hardly surprising, since a war between a shark and a minnow is not much of a risk for the shark. When minnows fought minnows, the initiator won 14 and lost 7, but when sharks fought sharks, the initiators won 3 and lost 5. Reiter and Stam [Reference Reiter and Stam2002] found 56 of initiators in the period 1816-1988 were winners, and only 30 were losers. However, if we add their draws (which are really a loss for both sides, costly in lives and money), we get 47 losers to set against the 56 winners. Lebow [Reference Lebow2010] found that initiators won 46, lost 45, and drew 6. And the states initiating the 9 biggest wars all lost them! His odds got worse: since 1945 only 26% of initiators achieved their goals. So when White [Reference White1990] studied only 20th century wars, he found that aggressors lost 20 and won only 5, with 5 draws—very bad odds.
These figures average out at around a 50% chance of success. Would you take the risk of initiating a war with only 50/50 odds? But millions of people today embrace projects with scant chance of success. Consider the booming global gambling industry. Its profit is projected to reach $565 billion in 2022. But the industry exists only if there are far more losers than winners. Gamblers are unreasonably hopeful. Clausewitz [(1832) Reference Clausewitz, Howard and Paret1976] noted that war is for states a major gamble on a very risky outcome. But one outcome is certain—mass killing. Of course, the rulers who initiate wars are gambling with other people’s lives, rarely their own.
Given the order to prepare for war, generals carefully calculate campaign plans and mobilize resources. Quartermasters’ logistics dominate this highly calculative phase of warfare. But then comes contact with the enemy and all hell breaks loose. Battle is experienced by terrified soldiers as fearful chaos, from the ferocious body-on-body slashing of earlier history to modern callous warfare in which soldiers blaze away at a distant enemy, keeping heads down, but vulnerable to a random death inflicted without warning from the skies. Carefully laid plans can rarely be implemented because of the enemy’s unexpected behavior or the unanticipated battlefield terrain. These were Clausewitz’s “frictions” of battle, Ibn Khaldun’s [(1377) Reference Ibn and Rosenthal1958] “hidden causes” of outcomes, and Napoleon’s oft-repeated comment, “No plan of operations extends with any certainty beyond the first contact with the main hostile force.”
Thus the outcome of six of the seven biggest battles of the Hundred Years’ War between England and France resulted from unexpected terrain or unexpected enemy action. The small-scale engagements by US World War II and Vietnam War units vividly described by S.L.A. Marshall [Reference Marshall1944, Reference Marshall1969] were decided by unexpected terrain or unexpected enemy dispositions, mistakes, good fortune, and individual bravery or cowardice. The decision for war submits rulers, generals, and soldiers to the fickle fortunes of battle. Today, as I write, that lack of predictability is obvious in Ethiopia, Yemen, and Ukraine.
Now consider earlier historical cases. The Roman senate did debate war and peace decisions openly and at length, often for a whole day. Yet debate focused on anticipated economic profit, not the cost in lives. However, Caesar’s wars in Gaul and Britain differed, since they were not expected to be profitable. Here the main motives, as so often in wars, were domestic politics. Most senators wanted the ambitious Caesar far away, where he could not foment trouble in Rome, while Caesar’s faction wanted him to command legions abroad and then bring them back to Rome to foment more trouble (which he duly did). Since the senators rarely doubted military victory, discussion of military odds was generally confined to how many legions should be mobilized. War was usually endorsed unless political jealousy stopped a rival senator from getting the chance to command the armies or unless ongoing wars were already stretching resources. They were sometimes over-confident, and defeat resulted. But their response was always to dig deeper into manpower resources and emerge with eventual victory. However, war for the Romans was not really a “choice”—it was what the Romans did, by virtue of their militaristic institutions and culture. In contrast, economic profit was more important for the Carthaginians, who did not sacrifice as much for war. So they lost the Punic Wars and were totally destroyed.
The rulers of the two ex-barbarian dynasties of China, the Yuan and the Qing, behaved like Romans. They also could dig deeper into resources than their enemies because militarism was baked-in to their institutions and cultures. As in Rome, war was considered the surest way to wealth, political power, honor, and glory alike. War was what Mongols and Manchus, Aztecs (Incas less so), Arab conquest dynasties, and many others did whenever opportunity or insult arose. They continued aggressing until defeated, which forced diplomacy on them—delayed-reaction Realism. But perhaps these aggressors were atypical.
So I examined the milder two Song dynasties of China. The first Song emperor, Taizu, was a model Realist, fighting and winning offensive wars after cautious initial probes to test whether victory was likely, and carefully building up adequate forces. Yet his successors initiated six offensive wars resulting in only one success, one costly draw, and four defeats. Muddying rational calculation were a self-righteous revisionism demanding the return of “lost territories,” attempts to divert domestic political power struggles, an emperor’s overweening ambition, or choosing the wrong allies, as in the crucial final wars of the two dynasties. Other Song rulers preferred peace or defense over aggression, less because of weakness than because they pursued economic and social development, following liberal, not Realist, precepts, and preferring diplomacy, cultural cooperation, production, and trade. In contrast, the last Song emperors (and the last Ming emperors, too) were weaker but hastened collapse by striking out impulsively, in denial of weakness, rather than settling for accommodation. The Song present a mixed bag, but not one favorable to Realism.
Moving to Europe, Luard claimed that most rulers between 1400 and 1940 who started wars lost them [Luard Reference Luard1986]. He surely exaggerated in perceiving no careful calculation of means among rulers, but war was mainly what a medieval ruler did when feeling slighted or ambitious or when diverting elsewhere the turbulence of younger sons or bolstering his or her own domestic power. These motivations and the lure of status, honor, and glory then dictated calling out the barons, levying taxes or borrowing, and setting off for battle with whatever levies showed up, which the ruler could not predict. Again, war was less a choice than what a ruler felt constrained to do in particular domestic and foreign contexts. Later European rulers fielded professional armies and navies of more predictable size, but they still warred when feeling slighted or ambitious. Conflict stances might escalate into unintended wars. From the 16th century came a wave of neo-mercantilist naval wars with more material goals. This was more calculative, although in other wars in this period religious ideologies were dominant.
In post-colonial wars in Latin America initiators lost six wars and won only two. There were also five mutual provocations and five costly stalemates. All eight of the rulers who initiated wars, whatever the outcome, were thrown out of office because of the war. Decision-making then became increasingly rational as rulers learned from bad wars not to make more wars. There were no serial aggressors here. A delayed reaction Realism made for lesser conflict or mediation, and a decline in warfare in the sub-continent.
In World War I no aggressor initially had economic goals. Instead, they demanded status in the geopolitical system and the honor of defending allied client states (though German rulers did hope for more profitable colonies). Many calculations were made by many actors, but war resulted from cascading diplomatic misunderstandings, mistakes, and incoherent policy formation. A wealth of political institutions produced unpredictability and brinkmanship that perversely meant that no one would back down. Most rulers were confident of victory, but they had a backup belief that this would be a short war, since economies could not support it for long. How wrong they were! So the rulers of Germany, Austria-Hungary, Russia, and the Ottoman Empire, the leading initiators, secured not only their own defeat but also the fall of monarchy itself. Some had warned of this, but they lost the domestic power struggles. All rulers lost heavily in this dreadful war, except for the two outsiders who picked up the pieces, the Americans and the Bolsheviks. This war was irrational for everyone else.
In World War II rationality was disrupted by ideology. This obstructed Allied defense strategy in the late 1930s. War might have been prevented or delayed if France and Britain had allied with the Soviets to deter Hitler. Ideology was the main problem: French and British rulers feared communism more than they did fascism. So Stalin, isolated, entered into his 1939 Non-Aggression Pact with Hitler. In the Far East, Japanese rulers underestimated Chinese nationalism, and Japanese and American rulers miscalculated each other’s reactions, resulting in their involvement in an unanticipated war. This war was initiated by German and Italian fascists and Japanese semi-fascists. Their economic motives were subordinate to the goal of imperial conquest by martial regimes believing themselves to be superior to the decadent liberal powers and China, and to the barbarous communists. The Axis rulers believed that martial spirit would overcome the daunting odds of numbers and technology. For them this war embodied Weber’s “value rationality,” with commitment to ultimate values overriding instrumental rationality. Their initiation of war and their escalation into war against more states was suicidal.
In the Korean War, North Korean, American, and Chinese rulers all in turn aggressed, underestimating their enemies, blinkered by ideology. They could reach only a bloody stalemate, which achieved none of their objectives and led to a bitterness across Korea that still poisons East Asia. In Vietnam the US suffered defeat by underestimating the ideological fervor and solidarity of their opponent. The recent spate of wars in Muslim countries has seen battlefield victories for the United States and its allies, yet neglect of political power relations predictably thwarted goal achievement. US interventions greatly damaged Afghanistan and Iraq and contributed to the chaos rending Libya, Syria, and Yemen. The United States has not achieved its goals in any significant war since 1945, apart from the Cold War, a remarkable series of failures by the world’s superpower. Putin also seems far from attaining his own ambitious goals. So from early history to the present day, initiating major war resulted more often in failure than success, while there was a substantial irrationality of means.
Nonetheless, some wars were rational in terms of ends, initiated for profit that was achieved. These were mainly raiding or imperial-conquest wars, especially between highly unequal adversaries, while wars of self-defense with a good chance of success must also be considered rational. In all of them the level of benefit was zero-sum: for some to gain, others must lose. The extreme example comes from wars of imperial conquest where imperialists were faced by much weaker indigenous peoples. This confrontation brought massive benefits to a few conquerors but led to massacres stretching up to genocide to the defeated.
Some wars might be considered rational in hindsight, having sparked unintended benefits such as economic development, while conquest may bring creativity by mixing together distinct social practices, as is nowadays argued for the Mongol Empire. Conquest may also produce more social order. Most imperialists have claimed this. Ibn Khaldun [(1377) Reference Ibn and Rosenthal1958 edition: 263, 355-365] noted that in early Arab wars conquerors seized great wealth for themselves and their followers, for “booty was lawful property,” but always at the expense of the conquered. He claimed that imperial rule did boost economic growth and tax returns for the first two generations of a dynasty, but then came decline leading to the collapse of the dynasty. During the modern period from the Industrial Revolution to the two world wars, the unintended benefits of war have been stressed by some [e.g. MacMillan, Reference MacMillan2020], but their evidence is weak and the benefits pale beside war’s devastation. The counterfactual of whether civilization could have been furthered better through peace may be unknowable. But in Song China peace favored major technological innovation and economic development—and defeat in war ensured the end of this surge in development.
The post-1945 period has seen extraordinary technological and economic progress, but was this due to American military hegemony or to the fact of peace in the northern hemisphere? Statistical data drawn from national income accounts since 1945 show that war has reduced GDP per capita, even though the main losses, of life and the destruction of physical and human capital, do not figure in these accounts [Thies and Baum, Reference Thies and Baum2020]. We cannot calculate such detail in earlier wars, but chroniclers say they were zero-sum and stress the devastation of regions in which campaigns occurred. I tried to end my cases with a rough guess at who benefited and who lost. Generally, many more lost than won. Given the certainty that war kills millions, most wars seem pointless and irrational in terms of both means and ends. Why are there nonetheless so many of them?
Political Power: Whose Decision?
We must first decide who to blame. Though the actors in most Realist accounts are states, it is human beings, or to be more precise, rulers and their entourages, who are the decision-makers. This has been the case almost regardless of whether we are dealing with a representative democracy, an oligarchy, a monarchy, or a dictatorship. In all, decisions were made by a small coterie of rulers, advisers, and other powerful persons—and sometimes by a single monarch, dictator, prime minister, or president. The extreme potential case, thankfully not yet realized, is the power of the American president to release nuclear missiles that could destroy the world (Putin or Xi could also do the same). We cannot blame whole nations or the capitalist class (except for colonial bankers and merchants, and arms and media barons). Most capitalists prefer to do business amid peace, although they adapt quickly to exploit profit from war. I show that, contrary to the views of most political scientists, modern representative democracies have been no less likely to make war, whether this was war against authoritarian regimes or other democracies, provided we include their sequences of small colonial campaigns and the direct democracy found among many indigenous peoples.
The people are rarely responsible for wars, not because they are virtuous but because they are barely interested in either sense of that word. They do not see their personal interests at stake, and they lack interest in foreign affairs. Representative democracy includes hundreds of elected persons sitting in parliaments. Yet they depend for reelection on their constituents, and so mirror their lack of interest in foreign policy. In the US Congress most representatives or senators leave foreign policy to the relevant committees. If their senior members agree with the administration, foreign policy is rubber-stamped, unless powerful interest groups intervene (or a gross violation of human rights provokes moralizing rhetoric). This is why congressional votes for war in the United States have been so lopsided. There is a plethora of think tanks add diverse opinions, yet congressional votes suggest that dissonant advice is ignored.
Public opinion does play more of a role in modern societies than in most historical ones, but amid popular ignorance it is manipulated by political leaders, entrenched interest groups, and media barons. Where geopolitics become fraught, foreign threats become “nationalized,” in the sense that the public are easily persuaded that national interests are at stake. Then as war starts, a period of rally ’round the flag lasts long enough to provide support to the rulers. Volunteers sign up in numbers, boosted by propaganda of the enemy’s atrocities, but then conscription is required. Soldiers continue to obey the order to fight since they are subject to military discipline. Varying degrees of value commitment among soldiers—high when defense of the homeland is at stake, or in highly ideological armies, less in most wars with professional or conscripted soldiers—are reinforced by repetitive drilling, harsh discipline, and entrapping battlefields. Yet a secret ballot held the day before battle would probably see most soldiers vote against joining battle, except perhaps in elite regiments.
Democracy is a desirable system for deciding domestic issues in which the people show interest. But democracy is absent from decisions on war and peace. The people have known little about the “enemy” beyond what rulers tell them. Past peoples saw war as a defense of their lord or monarch. Obedience was their duty, reinforced by institutionalized rituals and coercion. Today the people may identify with the nation and its rulers and so can be persuaded that an aggressive war is self defense or that the enemy is evil. Americans, for a time, and Russians now, support a war claimed to be carried out in self-defense or for good against evil, and leaders invariably assert both.
True, men in some societies have been addicted to war (and women accepted that addiction as normal), as for example many mounted pastoralist peoples of Eurasia and the Middle East. Decisions for war were made by the khan or emir and intimates, but there was a popular enthusiasm for war. More powerful at the global level has been a patriarchal ideology that smothers pacific tendencies among men with the smear of cowardice. Women are often complicit in this ethos. Fear of demonstrating cowardice in the eyes of comrades and women is then important in ensuring that men are willing to endure the horrors of battle. This is probably the most popular prop of militarism.
True also that in a few societies, quasi-representative decisions for war involved many more people. In some Greek city-states, decisions were made by the citizen body, 20-40% of adult males. Many were involved in some early Sumerian city-states, and apparently in the state of Tlaxcala, Mexico, in 1519, and among many Native American peoples. But the Roman Senate usually manipulated the popular assemblies into war. Parliaments in England generally left matters of war and peace to monarchs and their ministers, except during the mercantilist 18th century, when merchants and bankers joined in. 19th century British colonial policy debates consistently emptied the House of Commons, and the people showed interest in empire only when native atrocities committed against British people were publicized. Hitler’s lies about the murder of Germans in Danzig in 1939, Roosevelt’s distortion of the USS Greer’s 1941 brush with a German submarine, and Johnson’s distortion of the Gulf of Tonkin incident in Vietnam in 1964 were pretexts for war that were believed by most citizens. Bush the Younger and Tony Blair fed false information to gullible publics about Saddam Hussein’s supposed links with terrorists and weapons of mass destruction. In 2014, the Putin government denied that the masked men who seized Crimea were regular Russian troops, and in 2020 Putin claimed that Russian mercenaries and Russian planes in Libya were not Kremlin approved, although their weaponry could only have come from Russian army supplies. Putin’s lies about his war in Ukraine were many.
The US Congress is constitutionally empowered to declare war, but in the 20th and 21st centuries it has usually ratified decisions already made by presidents. Launching World War II was a partial exception. In 2001, during the panic induced by the 9/11 terrorist attack, Congress passed—with only one dissenting vote—the Authorization to Use Military Force Act, allowing the president to use force abroad without congressional approval if such conduct was in pursuit of terrorists or those who harbor them. The president decides who is a terrorist. The act is still in force. By 2018 it had been used 41 times to attack 19 countries.
Popular street demonstrations in favor of war or peace do occur, but the demonstrators generally make up small proportions of the population. War will become unpopular if it goes badly, or because of opposition to the consequences of war, namely conscription and additional taxes or debts. War and peace factions within ruling groups do exist; there is also lobbying by special interest groups, and students and intellectuals who mobilize for certain causes. That is as popular as war and peace decisions generally get. So the problem shifts away from why states or human beings make wars to why rulers do so. One inference is clear: the best antidote to war would be to have direct participation by citizens in popular assemblies to decide on war or peace. Alas, this remains a utopian ideal.
Rulers’ Rationality
Since rulers make wars, their varied preferences and personalities matter. Some rulers focus on stability, the economy, social welfare, or justice, and oppose conscription and higher taxes. Others favor war as profitable or heroic, necessary for grandeur and glory, and they willingly raise taxes and initiate conscription. Personal war records matter, since sequential victories enhance prestige and loyalty, making future wars more likely. Rulers are capable or incompetent, calm or impulsive, brave or timorous, suspicious or trusting. Contrast three successive Ming emperors: Yongle, the warrior; Xuande, the administrative innovator; and Zhentong, the incompetent. Contrast the cruel warrior Henry V with the mentally challenged Henry VI, the peace-loving Chamberlain with the bellicose Churchill, or the cautious, conscientious Biden with the erratic, ignorant Trump. In Latin America I attributed four of its fifteen wars to reckless presidents initiating or provoking wars they would probably lose. Since personality differences are contingent, Realists dismiss them as “noise” in their models, but we must not confuse models with explanation.
Monarchs, dictators, and presidents rarely make policy on their own. Most decisions come after rulers listen to opinions at court or in councils or assemblies. Yet rulers try to appoint like-minded advisers, and domestic political power relations also influence their perception of external realities. Debates over Japanese imperialism in the early 20th century were settled by the political power balance in Tokyo which shifted rightward due to the Great Depression, the repression of the working class, collapsing political parties, and assassinations of prominent opponents. So Japanese rulers shifted from international market nudging to informal empire to territorial imperialism. Since domestic issues dominate debate most of the time, war and peace decisions often depend on which faction dominated on domestic issues. Bush the Younger came to power on domestic issues, ignorant of the outside world. He allowed Vice President Cheney to make most of the appointments to foreign and defense posts, and Cheney chose hawks. They and a converted Bush launched wars.
Rulers also use wars to shore up their political power. Some Marxists stress attempts to use war to divert class conflict, but this has been uncommon since war is prone to increase rather than reduce class conflict, especially in defeat. It did figure in the reasoning of monarchs on the brink of World War I, but revolution was the consequence, as skeptics at court had warned beforehand. Diverting intra-elite conflict has been much commoner, launched by rulers beset by rivals or seeking to counter supposed weaknesses—like Taizong, Edward III or Henry V. Weak as well as strong rulers launch wars and they are often reluctant to back down since they believe this would signal weakness to a domestic audience. “Audience costs” [Fearon Reference Fearon1994] have loomed in all periods, among ancient Chinese dukes, the emperors Taizong and Chongzhen, the Emperor Claudius, medieval monarchs, leaders plunging into World War I, General Galtieri, and Saddam Hussein, among others. Monarchs may go further, wishing to prove that they really are the Son of Heaven or anointed by God. Putin wants to prove he really is Peter the Great.
Rulers may also fear their generals and weaken their armed forces to lower the threat of military coups. So they are less likely to initiate wars, but this may encourage others to attack them. For fear of his generals, Shah Muhammad II of the Khwarazmian (Persian) Empire separated his massive army into smaller detachments stationed in different cities. That allowed Chinggis Khan to pick them off one by one and destroy the Shah’s empire. The Roman Republic’s wars conversely enhanced the generals’ power, and they eventually overthrew the republic. Subsequent Roman emperors used praetorian guards for protection from the army. Inca and Middle Eastern regimes sought coup-proofing by reducing army power, and Saddam Hussein self-destructed in that way. Stalin almost self-destructed, purging his senior officer corps in the late 1930s. In contrast, few African rulers have devised effective coup-proofing. Between 2000 and 2020, 17 successful military coups occurred in a continent where military forces are deployed more for civil than for foreign wars. All these cases reveal a contradiction between military and political power. In contrast, most democratic and communist regimes have retained civilian control of the military.
There have been some differences according to regime type. Dynastic monarchies, the most common regime type, often had unclear rules of succession and polygynous marriages made for more wars in Europe, China, and the Inca Empire. The absence of a competent male heir might lead to civil war between claimants, inviting foreign interventions. Dynasties rarely lasted more than a hundred years, as Ibn Khaldun noted of Arab kingdoms. In succession crises only one claimant could win; those who lost would usually die. Hopeful ambition had bent their perception of the odds. Civil wars lasted for a quarter of China’s 2,000 year imperial history. Such wars rarely occurred in city-state republics like Venice and in elected monarchies, such as the Aztecs, where ruling oligarchies had agreed on procedures for choosing the next ruler. Modern republics, constitutional monarchies, and some one-party states have clearer rules of succession. Yet rulers’ personalities, reproductive abilities, ambitions, and constitutions all influenced war and peace decisions.
Rulers’ Motives
Three main motives for war stand out among rulers and their entourages. Historians usually emphasize two of them, “greed and glory”, while political scientists have explained civil wars in terms of “greed and grievance.” Those launching aggressive wars usually envisage economic benefits, promising them to their soldiers and subjects. However, acquiring more territories or tribute or submissive clients also brings rulers the gratification of greater status and honor, for themselves and for their states, which they see as identical. Glory is the highest level of status and honor, for it has the advantage, rulers believe, of being eternal, whereas profit is only for the now. So status, honor, and glory combine in an ideological-emotional package.
The third main motive is rulers’ intrinsic enjoyment of domination over others, found especially in raiding and conquest, particularly among the great conquerors of history. This was often shared by their followers who abused, looted, and raped enemy populations. American leaders today revel with somewhat more moderation in being “the leader of the free world” or of “the greatest power on earth”. These three motives—greed, status-honor-glory, and domination—repeatedly entwined in my case studies in ways that bent and distorted rational calculation.
Balancing economic costs and benefits against casualties and the likelihood of victory is at the core of Realist rationality, and rulers—and adventurist bands like the Vikings or conquistadores—had to try to assess these odds. Yet this involves four separate metrics, and there is no way to set lives, the odds of victory, economic profit or loss, and longer-term strategic advantages against each other in any systematic manner. The cost in lives was often irrelevant, as most rulers did not risk their own lives. They had begun in the center of battle formations, well-protected but still at risk, as Crassus and Richard III discovered. Accurate archery forced rulers and generals back to command from a vantage point in the rear, and then firearms forced them even farther back. By the 20th century they had become desk killers, sending out young men to distant deaths. Few campaigns have been abandoned because rulers feared heavy losses. They were more likely to intensify calls for “sacrifice,” which they were not prepared to make themselves. Putin exemplifies this tendency. Three recent US presidents who ordered wars were effectively draft dodgers themselves—Clinton, Bush the Younger, and Trump. In the past many rulers saw their soldiers as “scum,” drawn from the uncivilized lower classes, expendable. Modern soldiers have been wary of being used as cannon fodder. French troops in World War I demanded their sacrifice be “proportional” to the chances of success [Saint-Fuscien, Reference Saint-Fuscien2011]. In 2021 Afghan troops fled when their sense of proportionality was shattered by sudden American withdrawal.
The financial cost of war often did deter rulers since increased taxes or debts, and conscription are unpopular and take resources out of the economy. Many rulers were reluctant to squeeze peasants hard for fear of rebellion or damage to the economy, which would then reduce the taxes and men available for future war. Easy targets and short wars were not ruinous, nor were rule-governed wars with few casualties, while losing or lengthy wars might threaten a rulers’ downfall––though who could predict a war’s outcome? A few astute rulers devised reforms harnessing military and economic power together to yield economic growth that could fuel war—like the Legalist reforms of the Chinese Warring States, 16th century cadastral reforms in Japan, 17th century fiscal reforms in England and Holland, and 20th century military Keynesianism. Nonetheless, if economic profit was the sole motive of rulers, there would have been far fewer wars, since few wars do pay.
The Four Types of Aggressive War
The goals of raiding have been mainly material and sexual—looting movable wealth, animals, slaves, and women. Yet successful raiders also enjoy status and domination in itself, exulting in the fear in their victims’ eyes, especially evident in rape. Raiding was committed in Eurasia by “barbarian” horse archers, but it was common in all areas where peripheral peoples possessed some military advantages over more settled civilizations. Looting and raping survived among Nazi, Japanese, and Red Army troops in World War II, Chinese nationalist forces in Vietnam in 1945, Iraqi soldiers in 1991 and 2003, and Russian troops in 2022. Officers have either joined in or turned a blind eye.
Military intervention aimed at foreign regime support or change was frequent in the early phases of Roman and European empires and in pre-Columbian Latin America. Rule here was through local clients. It has persisted through the 20th and early 21st centuries in American military interventions aimed at informal empire without direct acquisition of new territories. For the moment, however, American rulers are quiescent, licking their wounds.
Wars over border territories are now the commonest wars. They involve mainly economic and strategic goals. Yet “revisionism,” a claim to recover “lost” or “stolen” territories, has added righteous self-justification to border wars. This subverted the pacific Confucian bias in imperial China, and it was prominent in the Hundred Years’ War and some Latin American cases. Timur the Great claimed to be only recovering Chinggis Khan’s realm. German revisionism led to World War II in an effort to regain territories lost in the first war. Russian revisionism today seeks to recover territories lost in the collapse of the Soviet Union. Chinese revisionism today seeks full control of Taiwan, Hong Kong, Tibet, Xinjiang, and offshore naval expansion—all formerly dominated by Chinese imperial dynasties. Restoring lost territory was deemed righteous by both Azeris and Armenians in 2020. Israelis and Palestinians find it impossible to negotiate a sharing of their promised but lost lands. Revisionism blends motives of moral right and economic and strategic interest.
But some contexts have produced fewer border wars. Post-colonial Latin America has seen fewer interstate wars in general. States had limited fiscal resources, enough to finance a brief war, but raising new taxes and loans created political discontent. Moreover, human settlement was easier in the ecological heartland of the new states (once indigenous peoples were removed) than near borders, which tended to be in mountainous, jungle, or desert regions. Since settler expansion was rarely located around borders, wars there were less likely. This was reinforced by the fact that most post-colonial states occupied the same area as a former Spanish provincial, treasury, or judicial district. This strengthened the legal principle of uti possidetis—new states should retain the old borders––and this assisted mediation of border disputes by outsiders. African countries also inherited colonial borders, discouraging border wars except in the Horn of Africa, where the British, French, Italian, and Ethiopian empires had left their own border conflicts to plague their successors. In Southeast Asia, most colonies inherited the territories of former kingdoms, which made post-colonial restoration of sovereignty easier. The successor states of the Habsburg Empire also inherited its provincial boundaries and so did most post-Soviet successor states. Most post-Soviet wars have been fought by a revisionist Russia against other peoples, as in the Caucasus and Ukraine.
Wars of imperial conquest add seizure of territory and direct rule over peoples. These wars have induced the greatest changes in the world. Conquerors like Qin Shi Huang, Chinggis Khan, Qianlong, the Japanese triumvirs, Caesar, and Napoleon carefully prepared their wars of conquest, signs of instrumental rationality. But their goals became the status, honor, glory, world transformation, and even immortality they believed their conquests would bring. They sacrificed countless lives to this vision. They saw their conquests less as choice than as an obligation to follow their destiny or the will of the gods, as probably did others like Sargon of Akkad, Thutmose III of Egypt, Tiglath-pileser III, Cyrus II of Persia, Alexander, Attila, Timur, Asoka, Pachacuti Inca Yupan- qui, and Aztec kings. They were given titles like “The Great,” “The Earth-Shaker,” “The World Conqueror”. They slaughtered millions and brought benefit to few. Most of these conquerors were highly intelligent, like Alexander, Chinggis and Timur. Ibn Khaldun, after interviewing Timur, commented [1958 edition: 12]: “Some attribute to him knowledge, others attribute to him heresy… still others attribute to him the employment of magic and sorcery, but in all this there is nothing; it is simply that he is highly intelligent and perspicacious, addicted to debate and argumentation about what he knows and also about what he does not know.” Timur also stated, “The whole expanse of the inhabited part of the world is not large enough to have two kings” [Barthold, Reference Barthold1956: 60]. Most great conquerors were intelligent megalomaniacs. They left triumphal stelae, arches, and sculptures whose grandiose inscriptions and depictions boast more of the territories and peoples conquered than of the well-being of the realm. We can probably add rulers of less well-documented pre-colonial American and African empires, such as Aztec rulers, the Songhai Empire’s Sonni Ali, or Chaka Zulu.
Of course, conquerors depended on loyal followers and obedient clients, on compliant, militarized subjects, and on the legitimacy of rule. They knew they had to extract material rewards for their followers and clients in addition to tribute and taxes for themselves, but they also knew that victories would cement follower and client loyalty and their own fame and wealth. Men would follow a leader who had been successful. Conquerors were trapped by success, compelled to continue it through a mixture of Durkheim’s “malady of infinite aspiration,” the need to keep rewarding followers, and the fear that the militarism they had cultivated might produce threatening rivals should their conquests end.
Conquest produced what are interchangeably called “empires” and “civilizations”—Egyptian, Akkadian, Assyrian, Roman, Hellenic, Persian, Turkic, Muslim Arab, Mughal, Mongol, Chinese, Spanish, British, Aztec, Inca, Maya, American, and so on. These imperial civilizations conquered numerous peoples, tribes, and city-states. They also developed mission statements claiming to bring order, freedom, civilization, and perhaps the true faith to the conquered, and these became motives or pretexts for further wars. They were also backed by large military budgets, justified in the American case by “defending democratic values”, a defense carried out through aggression to the world. We should be cynical about such claims.
The great conqueror is now obsolete. Putin’s invasion of Ukraine might be the last attempt at such an ideal, and it is failing. The rise of nationalism legitimizes states inhabiting a sanctified world order of states, while civil wars have largely replaced interstate wars, and electoral democracies produce short-term rulers. Rulers in the 21st century have aspired to notions of “greatness” more elevated than base profit but not amounting to conquest. Overall, wars have not declined through human history. However, some types have waned, especially those aimed at creating great civilizations. There is now one great global civilization, containing rival imperial cores exploiting their peripheries. But future wars between those imperial cores might end all human civilization, and 2022 has seemed to stoke such fears.
Ideological-Emotional Power
I have stressed the importance of ideologies and emotions. They fill in the gaps between our snippets of scientific knowledge, enabling action amid uncertainty, important since war is a risky shot in the dark. Emotions play a major role in descents toward war amid environments more conducive to anxiety and fever than calm––Realist anarchy. Disputes may escalate through minor provocations, hostile words, saber rattling, a clash of patrols, the sinking of a ship, maltreatment of citizens abroad, and rumors of atrocity. This fuels emotions. Publicizing the other’s atrocities makes further escalation likelier. Rivals are seen as “evil” or “terrorists.” America is the Great Satan, Iran was part of the Axis of Evil. Negotiating with evil is difficult. Hatred is countered not by love for the enemy but by pragmatic appeals for compromise. Emotions are invoked more for war, pragmatism for peace. Emotions also intensify during war, making it harder to disengage.
Aggression often involves rash overconfidence or exaggerated fear of an external threat, both boosted by a self-righteousness overriding contradictory information that might counsel peace. When both sides exhibit these emotions, damaging mutual brinkmanship follows. In the downward spiral of decisions leading to World War I, brinkmanship, reluctance to back down, maintaining rulers’ status and that of their states, and demonstrating fidelity to allies combined to follow a path of honor rather than reason. For Austria-Hungary and Russia, honor was seen as necessary for the dynasties’ survival. A monarchy without honor is illegitimate, said Habsburg and Romanov courtiers in 1914.
Lebow [Reference Lebow2010], analyzing 26 20th century wars, concluded that the failure of decision making was mainly due not to imperfect information or commitment problems (as Realists argue), nor to material interests (as Marxists and economists say), but to sentiments of honor, status, and revenge. Van Evera [Reference Van Evera1999: 192] examined modern cases of provocation by a ruler that caused others to start the fighting. He found that great powers had been overrun by unprovoked aggressors twice, but six times by aggressors provoked by the victim’s “fantasy-driven defensive bellicosity.” The major threat to states, he argues, is fear: “their own tendency to exaggerate the dangers they face, and to respond with counterproductive bellicosity.” White [Reference White1990] stresses the existence of overconfidence, arguing that 20th century rulers who started wars underestimated the target or the chances of others helping the target because of a “lack of realistic empathy with either the victims or their potential allies.” These studies did not include colonial wars where empathy was more lacking. Fear, overconfidence, and a lack of empathy confound rational decision-making.
The problem is that societies exert bonding effects on their members, as Durkheim argued. Ibn Khaldun called this asabiyya, normative solidarity, generating a collective will to pursue further goals. He argued this was the most fundamental bond of human society and the motive force of history, at its purest in Arab societies of his time. He emphasized bonding between followers and rulers, strong at the beginning of a dynasty, but then weakening as the conquerors merged with the conquered, losing their original tribal solidarity. In war asabiyya led to solidarity, commitment, and bravery by soldiers. I have found it especially in religious and communist forces and among freebooters far from home, like Vikings or conquistadores.
But normative solidarity has a downside: lack of empathy with and understanding of the enemy. Society is a cage, imprisoning the people within its stereotypes of the other. In wars, troops confidently marched singing into battle, expecting to return home soon, unable to imagine enemy troops at that moment doing likewise, with the same brio. Because rulers deny justice to the enemy’s cause, they underestimate the righteousness and morale of its soldiers. Putin is the latest example. Rulers view enemy resources opaquely, guided by external signifiers of strength, like rumors of political disunity or discontented generals, lower soldier morale, a supposedly inferior race or religion, cultural decline, or the accession of a child, a woman, or a supposed weakling (a comic actor perhaps) to power—blending understandable mistakes with self-delusion.
Overconfidence also results from blurring fact and value. Rational-choice theory strives to be scientific, keeping fact and value apart. “What is” governs the world, not “what should be.” This is something that we social scientists are all taught. Yet human beings do not operate like this, and that includes social scientists on our days off. We all blur fact and value. In war this most often appears as the belief that our cause is just, and so we should achieve victory. The English word “should” carries a double meaning—our cause is just, so victory is morally desirable, but also that our victory is probable. Both Union and Confederate soldiers were convinced that they should win quickly because their cause was just. In World War I, British troops should be back home by Christmas, German troops before the autumn leaves fell. Roman senators believed all their wars were just, blessed by the gods, generating righteous aggression. Chinese Confucian and Legalist theorists discussed the problem at length, mostly concluding that a just and virtuous ruler would defeat an unjust and despotic one because the people would offer him more support. Right makes might. Whether this is true is debatable, but if rulers believe their cause is just, they tend to think they should win (in both senses). If one side feels especially righteous, its morale may be higher and its battle performance better, as Chinese theorists and Ibn Khaldun argued, and as the Vietnamese PLF exemplified. But if both sides are self-righteous, the result is a more murderous war, like the Thirty Years’ War or World War II. For the protagonists, wars are moral as well as material.
Some ideologies are extreme, combining claims to absolute knowledge, distinguishing clearly between good and evil, and seeking to impose good on the conquered, perhaps through a religion or an ideology like fascism or democratic capitalism. Overconfidence and distortion grow. Putin demonizes Ukrainians. American administrations demonized the ayatollahs, Saddam, and Gaddafi. They were overconfident. Putin believed he would achieve a swift military and political victory; the Americans knew their military power would bring victory in the field but were deluded about political aftermaths. They believed in the global justice of their cause, and in good versus bad guys. They “should” be welcomed by Iraqis, they “should” be able to establish democracies.
Most ideological warfare against an “evil” enemy has been modern, contradicting Weber’s assertion of the increasing rationalization of modern society. I identified three modern waves of ideological warfare beginning in Europe: 16th and 17th century wars of religion; French revolutionary wars leading to 19th and 20th century wars of national liberation; and 20th century global wars between communist, fascist, and liberal capitalist regimes.
Some suggest a current fourth wave. However, although Islamic jihadists are strongly ideological, most recent wars among Muslims have not been, and they have also involved Western imperialism. Racial ideologies were also key to modern European and Japanese colonial wars. But they doomed their empires to a contracted life, preventing the assimilation of natives into the imperial identity, unlike peoples conquered by the ancient Romans and Chinese.
Symmetric and Asymmetric Wars
Three typical power balances affect the odds of success in war. The first is where one party is so superior in power resources that its victory seems certain. It may be immoral for sharks to attack and swallow minnows, but it may be rational. The second and third types are more puzzling. Why do minnows go to war against sharks, rather than submit? And why do evenly matched powers launch wars against each other, given probable mutual devastation?
Sharks have benefitted from gross military superiority, usually resulting from economic and political inequality. In ancient China and medieval Western Europe and Japan, as in pre-Columbian America, rulers mobilizing more efficient states in more fertile lands could achieve low-cost military victories against less well-developed peoples on the periphery, incentivizing aggressive war. Conquered lands were given to military veterans or settlers, and natives might be enslaved or enserfed. In Europe the core powers developed more effective states and more science-based capitalist economies, thereby conferring the military superiority that allowed them to briefly conquer most of the world. Gross power inequalities conferred by uneven economic development help explain why some regions and periods saw more wars of imperial conquest than others. However, the sharks need not conform to Realist theory by carefully calculating the odds. Their obvious superiority makes victory likely.
Yet history has not always favored the sharks. “Barbarians,” with their lesser economic and political development, had horse-archer superiority in flattish terrains over the bigger infantry-centered forces of agrarian states. Uneven modes of military development made war more likely, setting off a dialectic of warfare. Swift in-and-out raiding by war bands brought easy pickings, but repeated raids brought punitive retaliation from the agrarian state. In response, barbarian rulers developed loose tribal confederacies into states and added infantry and siege warfare. Both sides borrowed each other’s military techniques, fought combined arms warfare, conquered territories, and accepted some cultural merging. For the conquerors and their rewarded followers, this was highly rational, but it was not so for the masses. Did the scale of Emperor Qianlong’s warfare—mobilizing 600,000 soldiers and laborers in one campaign, committing genocide against the Zunghars in another—benefit the peoples of China? I doubt it, even though revisionist historians have bizarrely hailed his reign an Age of Enlightenment due to his artistic dabbling.
In recent years a great white shark has been thrashing amid the shallows. The United States has the world’s greatest armed forces, far superior to all others, yet it has not produced victories. US rulers cannot (and do not want to) directly rule foreign territories, nor can they find reliable local clients through whom they can rule indirectly, except where conservative elites share their goals. Nationalist and religious ideologies prevent the recruitment of many local clients, contrary to what was achieved by earlier empires. Where clients are recruited, this may exacerbate local ethnic or religious divisions—as in Afghanistan, Iraq, and Libya. Military interventions have brought disorder, and order is the primary political goal of most peoples, on which any democracy must be grounded. Second, weapons of the weak (the guerrilla cell, the Kalashnikov, the suicide bomber) can sustain asymmetric warfare against a conventionally superior enemy. Third, most Americans are only armchair warriors, unwilling to enlist or to see wars drag on if they cause many American casualties. The fiscal cost is no obstacle, but the human cost is. American society, despite its proliferation of guns, is not at its core militaristic. But these weaknesses ensure that American wars are not just understandable mistakes. They predictably fail, and so are irrational in terms of ends.
The other face of asymmetric warfare occurs when minnows fight instead of suing for peace and negotiating. Rulers who submit can usually keep their domains if they swear allegiance to the more powerful or shift toward compliance with its policies. Some did take this route to survival, and some conquerors encouraged this, as for example did the Inca. Saddam Hussein could have survived this way, as do other dictators who cozy up to the United States. However, in many cases minnows choose to fight. They may count on help from allies. Yet allies’ words may not translate into deeds, or they may be bribed into switching sides. Sometimes the sharks even feast together on the minnows lying between them. Poland was partitioned three times by its neighbors. Balancing only works if normative trust or strong mutual interests are shared by the allies.
Minnows are also often overoptimistic because of the tyranny of history. Having survived a sequence of wars against lesser foes, they are unprepared for a superior one, and their national cage limits an accurate perception of the enemy. When war is carried out in self-defense, they also believe their cause is just. They “should” win, as Ukrainians believe. Native people confronting the first waves of European imperialists were unaware that behind these small forces would come wave after wave of soldiers and settlers. In modern times only the Japanese and then the Chinese found the space and time to build up effective resistance to foreign imperialists. Minnow rulers may also feel compelled to fight to maintain honor and status. Feudal rulers often went down fighting with honor, believing they had no choice. Saddam self-destructed for status and honor. He did not want to be seen as complying with US demands on chemical weapons (when he really was) because defiance was his badge of honor. He thus contributed to his own doom.
The proliferation of vanished kingdoms undermines defensive Realism’s belief that survival is the major goal of states. Overwhelmingly they have failed to survive. This was not true of post-colonial Latin America, where balancing against would-be hegemons was successful in six wars (and failed in none). After the 1830s all its states survived. In contrast, only one of over 70 polities in post-Zhou China survived. 16th century Japan saw over 200 polities reduced to just one. The more than 300 states of Europe were whittled down to 30 by the 20th century. An unknown but large number of states and tribes disappeared from pre-Columbian America and from around the Mediterranean under Roman pressure.
Human civilizations have expanded by eliminating most of the world’s polities. Elimination might come through defeat in war, submission to the threat of force, or marriage or inheritance contracts. In three studies, of 16th century Japan, medieval and modern Europe, and the world since 1816, most vanishing states died in battle, say Bender [Reference Bender2008], Davies [Reference Davies2011], and Fazal [Reference Fazal2004]. However, in pre-Columbian America threats usually sufficed for submission to the Inca, and the Aztecs combined war and intermarriage. This type of warfare was zero-sum: for some to gain, others must lose; but since the losers disappeared, so did their history. Recorded for posterity is the success of imperial civilizations.
But states no longer vanish. Iraq survived when Saddam was killed, for the survival of states in the post-1945 world is guaranteed by international and nationalist norms. Rulers are defeated and killed, but their countries survive. The world is filled with states whose legitimacy is supported by international institutions. Most contemporary battlefields have been transferred to the spaces inside weak states.
There is finally symmetric warfare between near equals, like Greek city-states, the Chinese Warring States, Han Chinese dynasties struggling against ex-barbarian empires, wars among the major Japanese daimyo, and wars between the major powers of modern Europe. Some rulers were tempted into attacking a near equal since by occupying enemy soil their troops could live off the land, wasting enemy resources while not wasting their own. But soldiers defending their own soil might fight with greater determination, as in Ukraine. Defenders could also retreat, laying waste to lands in the path of the invaders, preventing them from living off the land, and lengthening their supply lines. Such invaders either became bogged down in stalemate or they had to retreat.
Great power wars seem irrational because of the scale of destruction and death. Yet there were two ways to lessen the pain. The first was to develop rules of wars that kept the death rate in battle low for the dominant classes. This was extreme in Aztec “flower wars,” but common in China during the Spring and Autumn period, and in Europe in the Middle Ages, and then again in the century following the Peace of Westphalia in 1648. War was not absent then, but it was regulated, which reveals a rational calculation of ends. War might not be so costly—for rulers and the upper classes at least.
Wars of deflection might also lessen the pain. In ancient China and in Europe, wars between the major core powers could be partially deflected onto weaker peoples on the periphery or onto the enemy’s lesser allies. Empires were built on expansion into the peripheries, much as Rome expanded around the Mediterranean, or Zhou dynasty Chinese rulers expanded among the “people of the field”. When Britain and France fought each other across the world in the 18th century, their peace treaties typically conferred territorial gains on them both, at the expense of colonized natives. There was a division of the spoils between the foreign powers in the “Scramble for Africa” and in late imperial China, where foreign allies all provided troops for a force to repress Chinese resistance. Wars of deflection cost less and so major Asian and European powers could expand cheaply across their peripheries and into the entire world. The Cold War deflected superpower conflict onto lesser clients as the United States and the Soviets fought indirectly, in proxy wars using client states and movements, a rational strategy for the superpowers, though not usually for their clients. But in the long run, there were fewer and fewer possibilities for deflection, as the smaller kingdoms vanished. War was now mainly a life-and-death struggle between sharks, predictably in the form of costly frontal battles against each other. Why did they continue fighting each other?
Again, the preservation of status and honor was important, but so were ideologies and contexts invoking anxiety, fear, and hatred of “evil” rivals, as in the European-initiated waves of ideological warfare. Here the aggressor wished to transform the society of those it attacked, while the latter wished to protect its own way of life. The most extreme example of this was Soviet resistance to Nazi Germany, for death or slavery awaited Jews, communists, and even all Slavs if the Nazis won. For these groups, self-defense involved a truly desperate survival rationality.
But more frequently the aggression of sharks against equals resulted from path dependence—rulers were tempted to follow the paths that had brought past successes. Victories begat confidence, which made war a more likely outcome of a dispute. Cumulative swallowing meant that Rome, the last few Chinese Warring States, the last few Japanese daimyo, and the surviving major rulers in early modern Europe had grown accustomed to victory. Most finally got their comeuppance, but sequences of victories had baked-in the culture and institutions of militarism. Martial culture strengthened and rulers perceived war, not trade, as the path to wealth, career success, social status, honor, and glory. Military power was elevated over other sources of power. The Roman Republic was the extreme case of baking in. However, although Roman militarism was unusually long-lived, war was also baked-in to the Warring States of China, the ex-barbarian dynasties ruling imperial China, the Aztec and Inca dynasties, the early rulers of Arab dynasties, 16th century daimyo lords in Japan, medieval European princes, Prussia-Germany and Japan in modern times, and Putin’s Russia. Wars are historical sequences in which the experience of past generations lies heavily on the minds of the living, sometimes (as Marx argued) as nightmare, but more often in the case of war as pleasurable fantasy.
Conversely, repeated war defeats or costly draws lower ambition, undermining militarism—a delayed-reaction Realism, as in imperial Rome after repeated inconclusive wars with the Parthians and northern barbarians. Japan’s terrible civil wars in the 16th century produced a widespread yearning for peace, which Tokugawa policies were able to provide for over 200 years. More common was a short-term effect. Four times in Europe its worst wars—the Thirty Years’ War, the Napoleonic Wars, World War I, and World War II—produced a post-war period of diplomatic peace. In the first three, this was temporary. The fourth now seems fragile. China under some Han and Song dynasty rulers reacted to defeat with conciliatory diplomacy, as did American politicians for a decade after defeat in Vietnam. The recent spree of unsuccessful wars may not result in long-term caution by American rulers since they have discovered risk transfer militarism, the contemporary form of wars of deflection, deflecting the risk of death away from one’s own troops onto enemy soldiers, civilians in war zones, and hired contractors and mercenaries, all dying far from the public gaze. From an American perspective, the war in Ukraine is a perfect storm, weakening Russia by expending Ukrainian lives and American dollars, but not American lives.
Conclusion
I began with the question why rulers choose war to achieve ends rather than relying on softer sources of power—economic exchange, cooperative ideologies, or geopolitical diplomacy. Rulers do exercise some freedom of choice. But choice is not quite the right word, since decisions also embody social and historical constraints of which the actors are not wholly aware, constituting part of their taken-for-granted reality. Sociology sees humans as creating social structures, which then become institutionalized, constraining subsequent action. Wars have to be studied not merely as individual cases to be fed into quantitative models, but as historical sequences of purposive action. War and peace decisions are influenced by “path dependence”, constraints inherited from the past, involving overconfidence, national caging, emotions, ideologies, domestic politics, and baked-in militarism. There are multiple levels of war causes—motives, emotions, ideologies, as well as ecological, geopolitical, and historical contexts, and erratic processes of escalation. Their varied interactions through time and space certainly subvert Realist rationality but they also defeat any simple causal theory. In response, some Realists have broadened rational choice to include all these factors, but their different metrics make it difficult to assign them relative weights. In addition, if all these factors are regarded as rational, the theory becomes circular and we cannot identify irrationality.
I have simplified the range of motives for war-making, identifying a triad of reasons: greed, status-honor-glory combination, and the enjoyment of domination. It is therefore obvious that rationality cannot dominate rulers’ decisions to go to war. They were sometimes careful, calculating pros and cons, but miscalculation occurred too often to support a rational-choice model, with the exception of a delayed-reaction rationality, whereby rulers realized they had bitten off more than they can chew. But in an age of nuclear weapons and climate change, delayed-reaction Realism might be too belated to permit human survival. Combined economic and military power—seizing material resources through war—is the heart of Realist and Marxist theory. This is sometimes rational for the winners, although it is overwhelmingly zero-sum: for some to benefit, others must suffer. But the perennial intervention of emotions, ideologies, and political motives weakens the rationality of warfare.
The offensive wars that go according to plan are mostly those in which sharks attack minnows, or in which wars among the sharks are deflected onto the minnows. Since the winners write history, and the losers vanish, victory in war is seen as commoner, more profitable, more rational, and more glorious than it really has been. But war rarely pays, for all sides lose where war involves material costs greater than its spoils can justify, where there is no clear winner, or where war does not resolve the dispute in question. These constitute the majority of wars. Raiding might pay off if it does not become too repetitive, in which case retribution comes. Regime change or support might be done cheaply, as in 19th century Latin America, or expensively and without much success as in recent American ventures. Some wars over slivers of border territory have brought benefit for the winners where valuable economic or strategic resources were obtained, but these wars are also intensified by emotional revisionism. Imperial wars of conquest benefitted victorious rulers and attendant merchants, bankers, settlers, clerics, and officials of the empire—but not usually the colonizer’s people as a whole, and certainly not the exploited, enslaved, or exterminated peoples. Wars conducted in self-defense are generally considered as rational and legitimate, and indeed some are. However, in many, submission would be more rational. The benefits of war are rarely widely shared.
War is the one instance where losing one’s temper may cause the deaths of thousands. War pays us back more swiftly for mistakes than any other human activity. Humans are not calculating machines—more’s the pity, since peace is more rational than war. If the social world did conform to Realist theory, if rulers did carefully calculate the costs and benefits of war, trying hard to set emotions and ideologies aside and ignoring domestic political pressures, they would see that most wars are inferior to economic exchange, the sharing of norms and values, and diplomacy as ways of securing desired goals abroad. Realism is fine as a normative theory, showing rulers how they should act for maximum benefit, but it is not a description of reality, for they do not act in this way. We need more Realism, for this would bring the benefits of peace!
War is the least rational of human projects, but humans are only erratically rational, as we know from our everyday lives. Rulers are asked in matters of war and peace to make decisions with momentous consequences, armed with the sketchy information, the ideologies and the emotions of their imprisonment within their society amid anxiety-producing, unfolding environmental and geopolitical constraints and the tyranny of history. The task of surmounting this is often beyond the capacity of rulers, as it would be beyond ours too. Human beings are not genetically predisposed to make war, but our human nature does matter, if indirectly. Our tripartite character––part rational, part emotional, part ideological––when set inside the institutional and cultural constraints of societies, makes war a persistent outcome. Human nature does matter, which is why when wars are fought, this is rarely for good reason.
Han Fei remarked in the third century BCE that, “No benefit is more constant than simplicity; no happiness more constant than peace.” It is better and simpler to choose peace, which is more rational, less lethal, more comfortable, and less risky, tomorrow being more or less like today.
