INTRODUCTION

Confronting Civil War

Since 1945, Europe, North America, and countries of comparable wealth elsewhere, like Australia and Japan, have experienced what has been termed a “Long Peace.” Coming in the wake of World War II, this period without war between states now stands as the most enduring in modern history. Previously the calmest moments, within Europe at least, ran from the end of the Napoleonic Wars to the Crimean War (1815–53) and then from the Franco-Prussian War in 1871 to the beginning of World War I in 1914, but the recent international peace in the Global North has already lasted two decades more, even if overshadowed by the Cold War for much of its duration.¹ Current global trends are also encouraging. In 2015, the latest year for which figures have been calculated, there was only one interstate conflict, between India and Pakistan, with barely thirty casualties; in the previous year, there had also been only one.² Despite Russian intervention in Ukraine and the combustible disputes over islands in the South China Sea, the Long Peace increasingly looks as if it might expand and become all encompassing around the globe.

And yet our own age is plainly no piping time of peace. The world is still a very violent place.³ In 2015, there were more than forty armed conflicts in progress from Afghanistan to Yemen, not counting acts of terrorism, insurgency, or other forms of “asymmetrical” warfare, in which non-state forces attack states or their inhabitants. The activities first of al-Qaeda and now of Islamic State (Daesh) and its sympathizers have brought the weaponry of war onto the streets of the world’s cities, from Manhattan to Mumbai and from Sydney to Brussels. While states may, in fact, be at peace with one another, their peoples can hardly feel at ease or secure amid the effects of conflict taking place afar, where so many still know war within their own borders. The Long Peace stands under a dark shadow—the shadow of civil war.

In the early 1990s, theorists of the “end of history” assured us that capitalism and democracy were poised to blanket the globe, uniting all humanity in the enjoyment of flourishing trade and secure rights. Subscribers to such thinking argued for the so-called democratic peace, the view that as democracy spreads, universal peace would follow in its wake because democracies (they allege) do not go to war with one another. They built on the arguments of the philosopher Immanuel Kant (1724–1804), who in turn drew on the European Enlightenment’s long tradition of discourse on the possibility of securing lasting peace.⁴ Kant was no naïf; he wryly observed that a Dutch innkeeper had painted the very words “perpetual peace” on his tavern sign alongside a picture of a graveyard, implying that the only true and lasting peace would be the eternal sleep of death. Yet Kant believed that peace among states was “no empty idea” but rather “a task that, gradually solved, comes steadily closer to its goal.”⁵ Not that perpetual peace would draw any nearer in his own lifetime: the great general and empire builder Napoleon was crowned emperor only ten months after Kant died in February 1804 and would spend the next decade menacing the world. Even so, a little over two hundred years later, many dare to believe that humanity might finally have moved beyond armed conflict between states—that following “the better angels of our nature,” we may well be able to fulfill Kant’s dream and at last “win the war on war.”⁶ Yet with death and destruction all around us, the peace we have feels more like that of the graveyard. And more than any other form of conflict, the one that has lately filled the graveyard is not war between states, not terrorism, but civil war.

Civil war has gradually become the most widespread, the most destructive, and the most characteristic form of organized human violence. The decades following the Cold War saw a major spike in its incidence. Since 1989, an average of twenty intrastate wars have been in progress at any moment—about ten times the annual average globally between 1816 and 1989. There have been roughly twenty-five million “total battle deaths” in these wars since 1945, or about half the military casualties of World War II. Even that count does not include wounded, displaced, and dead civilians, let alone all those afflicted by disease and malnutrition. The material and economic costs have been no less staggering. Hard-nosed analysts of global development have focused on the impact of war on growth, factoring in the loss of life and, consequently, of productivity, as well as the value of wasted resources, military spending, the spread of crime and disease, and the disruption of neighboring economies. The result of their calculations? The annual price tag for civil war has been about $123 billion—roughly what the Global North budgets for economic aid to the Global South each year. Not without reason, then, has civil war been chillingly described as “development in reverse.”⁷

Wars within states tend to last longer—some four times longer—than wars between them, and in the second half of the twentieth century they have generally lasted three times as long as in the first half. These conflicts are also much more prone to recur than any others, as “the most likely legacy of a civil war is further civil war”; indeed, almost every civil war in the last decade was the resumption of an earlier one.⁸ Civil wars seem disproportionately to befall the world’s poorest countries—especially those in Africa and in Asia—which the development economist Sir Paul Collier has called “the bottom billion.”⁹ If the developed world has enjoyed a long peace since 1945, large parts of the global population have undergone an equally long trauma. The Centre for the Study of Civil War in Oslo proclaims all these distinctions on its website, adding, “Yet civil war is less studied than interstate war.”¹⁰ It seems that civil war, like the poor, may always be with us. And so long as it is, it will generally afflict the world’s poor.

But civil war shouldn’t also remain an impoverished area of inquiry. As many have noted, civil war has remained undertheorized and resistant to generalization. There is no great work titled On Civil War to stand alongside Carl von Clausewitz’s On War or Hannah Arendt’s On Revolution;indeed, as we shall see, Clausewitz hardly discussed civil war at all, while Arendt herself dismissed it, along with war itself, as atavistic and antimodern. The postwar German poet and political commentator Hans Magnus Enzensberger (b. 1929) observed in 1993 that “there is no useful Theory of Civil War.”¹¹ So, too, the Italian political theorist Giorgio Agamben (b. 1942) has noted more recently that “there exists, today, both a ‘polemology,’ a theory of war, and an ‘irenology,’ a theory of peace, but there is no ‘stasiology,’ no theory of civil war.”¹² Such laments are long-lived, too. It is not my aim to provide an overarching theory of civil war. Nor can I supply that missing treatise. What I can do as a historian is to uncover the origins of our present discontents, to explain just why we remain so confused about civil war and why we refuse to look it in the face.

Our own time demands an unblinking encounter with civil war. The three hundred years between 1648 and 1945 constituted an era of war between states; the last sixty years appear to be an age of war within states.¹³ Indeed, this is the most striking change in patterns of human conflict for centuries. According to one widely cited estimate, since 1945 there have been 259 conflicts around the world that have risen to the level of a war, and the vast majority of those were internal conflicts. Since 1989, barely 5 percent of the world’s wars have taken place between states. One has only to think back to the Balkan wars of the 1990s, or to those in Rwanda, Burundi, Mozambique, Somalia, Nicaragua, and Sri Lanka, for instance, to realize how prominent and how deadly internal struggles have been in recent memory, to say nothing of the ongoing suffering of those who live in their wake. To make matters even worse, civil wars do not usually stay “civil” for long. In 2015, twenty of the fifty internal conflicts, from Afghanistan to Yemen, were so-called internationalized civil wars, ones that drew in forces from neighboring countries or intervention by outside powers.¹⁴ Civil war is no respecter of borders. Indeed, it often turns countries inside out, as conflict drives people from their homes in search of safety. The populations displaced by civil war—not least the almost five million refugees from Syria over the course of the conflict there since 2012—are the most conspicuous victims of its overspill. Their plight has fueled a refugee crisis that will reshape the Middle East, North Africa, and Europe for generations. The attendant challenges to security and stability make it appear that ours is not a world at peace. It is a world of civil war.

*

War is hell, the U.S. Civil War general William Tecumseh Sherman is supposed to have said, but surely the only thing worse is civil war.¹⁵ On that fact, there has been general agreement across the centuries. Internal wars are felt to be more destructive than ones against external enemies. Writing in the wake of Rome’s civil wars, in the first century B.C.E., the poet Lucan concluded from the shattered cities, abandoned fields, and droves of the dispossessed, “No foreign sword has ever penetrated / so: it is wounds inflicted by the hand of fellow-citizen that have sunk deep.” Civil wars are like a sickness of the body politic, destroying it from within. Likewise, the Renaissance essayist Michel de Montaigne would warn his readers during the French Wars of Religion, “In truth a forraine warre is nothing so dangerous a disease as a civill.” Dangerous and morally degrading, too. Just before the Irish Civil War of 1922, an elderly priest lamented, “War with the foreigner brings to the fore all that is best and noblest in a nation—civil war all that is mean and base.”¹⁶ And even when the battles have ceased, they leave wounds that will not heal: “I question whether any serious civil war ever does end,” T. S. Eliot observed in 1947.¹⁷ On a visit to Spain in 1970, the former French president Charles de Gaulle agreed: “All wars are bad…But civil wars, in which there are brothers in both trenches, are unforgivable, because peace is not born when war concludes.”¹⁸

Civil wars are doubtless inhumane but they have been so widespread and persistent that some have suspected them of being essential to our humanity. As Hans-Magnus Enzensberger argued, “Animals fight, but they don’t wage war. Only man—unique among the primates—practises the large-scale, deliberate and enthusiastic destruction of his fellow creatures.” And what could be more characteristically human, yet more shamefully different from the habits of other animals, than inflicting aggression on your immediate neighbors? Formal warfare, conducted by professional armies and constrained by the laws of war, was something modern and recent, but what lay behind the outward show was a more basic, more enduring, form of inhumanity: civil war. “Civil war is not merely an old custom,” Enzensberger concluded, “but the primary form of all collective conflict.”¹⁹

Enzensberger was writing in the shadow of ethnic conflict in Africa and the Balkans and not long after the Los Angeles riots of April–May 1992 that followed the acquittal of police officers for beating an African American motorist the previous year. This was just the moment when human-on-human violence seemed to be cresting around the world, across continents and within cities, as if to reassert the prevalence of what is worst in humankind and to confirm our destiny as civil warriors. Enzensberger could be forgiven for assuming that civil war had always been with us. So many of the world’s primal myths—Krishna and Arjuna in the Mahabharata; the Hebrew Bible’s Cain and Abel; Eteocles and Polynices in Greek mythology; Romulus and Remus for the Romans—concern internecine violence, specifically fratricidal violence, in a way that suggests it is foundational.²⁰ Such myths can help us grasp the emotional dimensions of conflict but their durability should not be mistaken for civil war’s inevitability.

Long-lived too is the reputation of civil war as the most destructive and invasive of all kinds of human conflicts—and with good reason. At the height of Rome’s civil wars in the first century B.C.E., perhaps a quarter of all its male citizens aged between seventeen and forty-six were in arms.²¹Seventeen hundred years later, a greater proportion of England’s population likely died in the civil wars of the 1640s than would later perish in World War I.²² And the death toll of the U.S. Civil War was vastly larger, relative to population size, than the American casualty rate in World War II: estimated at 750,000, from both North and South, it would be equivalent to roughly 7.5 million deaths among the present-day population of the United States.²³ Slaughter on such a scale scythes through families, shatters communities, shapes nations. It can scar also imaginations for centuries to come.

Yet we should be cautious about assuming civil war is an inevitable part of our makeup—a feature, not a bug, in the software that makes us human. For that would be to doom us to suffer civil war ad infinitum, never to reach Kant’s promise of perpetual peace. To unsettle the notion that we are condemned to interminable civil war, rather than destined for perpetual peace, I here bring historical tools to confront the challenge of civil war. Over the course of this book, I show that civil war is neither eternal nor inexplicable. I argue that the phenomenon is coterminous with its historical conception, from its fraught origins in republican Rome to its contested present and its likely no less confusing or controversial future. It has a history with an identifiable beginning, if not yet a discernible end. A historical treatment reveals the contingency of the phenomenon, contradicting those who claim its permanence and durability. It is my aim to show that what humans have invented, they may yet dismantle; that what intellectual will has enshrined, an equal effort of imaginative determination can dethrone.

My goal is not just to excavate the history of civil war but to point up its significance in forming how we think about the world. I argue that despite its destructiveness civil war has been, throughout history, conceptually generative. Without the challenges it posed, our conceptions of democracy, politics, authority, revolution, international law, cosmopolitanism, humanitarianism, and globalization, to take just a few, would have been very different, even poorer.²⁴ The experience of civil war—the efforts to understand it, to ameliorate it, even to prevent it—has also shaped and continues to inform our ideas of community, authority, and sovereignty to this day. Civil wars spring from deep and deadly divisions but they expose identities and commonalities. To call a war “civil” is to acknowledge the familiarity of the enemies as members of the same community: not foreigners but fellow citizens. “Civil war has something atrocious about it,” remarked the German legal thinker Carl Schmitt (1888–1985). “It is fraternal war, because it is conducted within a common political unit…and because both warring sides at the same time absolutely affirm and absolutely deny this common unit.”²⁵ That is the source of our horror about civil wars; we should not underestimate the effect of civil wars in forcing a recognition of commonality amid confrontation, of making us see ourselves in the mirror of enmity.

Civil wars have been so paradoxically fertile because there has never been a time when their definition was settled to everyone’s satisfaction or when it could be used without question or contention. This is in part because conceptions of civil war have been disputed and debated within so many different historical contexts. Naming, however, is always a form of framing. Understanding an object means first distinguishing it from similar things, and that often entails settling its identity by taming it in words. Once we can see what makes it peculiar, we can begin to recognize patterns, continuities, and differences, thereby developing our understanding.

This problem of naming becomes particularly acute when political ideas are at stake. We frame these terms to persuade our friends and to combat our enemies. And we have to invent new terms for new phenomena, both to make sense of them—what is this we are experiencing?—and to help others share our conception of them. When the framing term is one like “civil war,” however, politics precedes even attempts at definition. What makes a war “civil” rather than, say, “foreign”? That difference will always raise hackles. And what makes violence identifiable as “war”? Again, wars have implications that serial skirmishes do not. Even to ask these questions demands fixing some points at least: an idea of what is “civil” (and what is not), as well as what counts as war (and what does not). It has never been easy to decide what is, or is not, a civil war, but that distinction was literally inconceivable before the category had been invented.

Civil war is not solely in the eye of the beholder, but the use of the term is itself often one source of strife among the combatants. Established governments will always view civil wars as rebellions or illegal uprisings against legitimate authority, particularly if they fail. The Earl of Clarendon (1609–74) titled his Royalist account of England’s mid-seventeenth-century troubles The History of the Rebellion and Civil Wars in England (published in 1702–4) precisely to deprive the “rebels” of legitimacy.²⁶ For the same reason, the seventy-volume official history of the U.S. “Civil War” published between 1880 and 1901 was called The War of the Rebellion, a title clearly meant to deny standing to the defeated “rebels.”²⁷ By contrast, the victors in a civil war will often commemorate their struggle as a revolution, as did those in the American and French “Revolutions,” for example. It’s easy to perform the conjugation: I am a revolutionary. You are a rebel. They are engaged in a civil war.

For those of us lucky enough to live under the reign of the Long Peace, civil war is more a matter of memory and metaphor than lived experience. Civil wars now take place as historical reenactments and science-fictional video games, and more seriously in the debates of assemblies and power struggles of political parties. For example, in 1988, the U.S. congressman Newt Gingrich described American politics as if it were a civil war: “The left at its core understands in a way Grant understood after Shiloh that this is a civil war, that only one side will prevail, and the other side will be relegated to history.” He then sketched out the terms of the fight: “This war has to be fought with the scale and duration and savagery that is only true of civil wars. While we are lucky in this country that our civil wars are fought at the ballot box, not on the battlefields, nonetheless it is a civil war.”²⁸ More recently, in the aftermath of the Daesh terrorist attack on Paris in November 2015, the French prime minister, Manuel Valls, charged that the right-wing National Front was stirring up civil war in France. “There are two options for our country,” he said. “There is the option of the extreme right which, basically, foments division. That division can lead to civil war [guerre civile], and there is another vision, which is that of the Republic and its values, which means pulling together.”²⁹ As I write, the instability of party politics has fomented charges of “civil war” among Republicans in the United States, within the British Labour Party, throughout Brazil’s fractious political elite. Around the world, democratic politics now looks ever more like civil war by other means.

Civil wars are everywhere, in the headlines and on the ground, in hearts and minds, as well as in commemorations of civil wars past. Some countries have thought themselves free from civil war. Others can hardly imagine themselves except through the memory of it: the United States, for one. And the international community perceives still others—Iraq, for example—as the perpetual battleground of unending civil wars. The benefit of history, and perhaps the curse of remembering it, is the knowledge that civil war has never been quite as stable or transparent a category as its popular usage would imply.

Yet how do we tell civil wars apart from other kinds of wars, when so many internal conflicts spill over their countries’ borders or draw in combatants from outside, as happened in Liberia and Rwanda in the 1990s as well as Iraq, Afghanistan, and Syria more recently? Can such wars even be considered “civil”—in the sense of taking place among fellow members of the same community—when insurgent groups comprise transnational elements, like al-Qaeda, or deliberately set themselves against the existing world order of states by proclaiming their wish to form supranational communities like the caliphate pursued by IS/Daesh? Is every civil war really a specimen of the same species, when so many distinct dynamics—ethnic conflicts, wars of secession and national liberation, battles for succession, and so on—can be found across history and around the world and when local contexts may make it impossible to analyze specific incidents of violence as part of larger patterns of collective action?³⁰ Can we distinguish particular civil wars from any larger global phenomenon of “new” wars in the aggregate?³¹ What, in short, is civil war?

Any complex idea like civil war has multiple pasts. Historians can show the paths not taken as well as the many and winding roads by which we came to our present understandings. One fashionable term of art for this procedure is “intellectual genealogy.” This method does share some features with tracing family history: it digs back through the past; it searches for roots; it is always open to wandering along the byways of a tangled history. But there are also important differences.³² Genealogical research fastens on continuities: who descended from whom, who begat whom. And if the overall aim of family genealogy is self-affirmation, intellectual genealogy encourages skepticism and humility. It traces breaks or discontinuities and shows how our own arrangements are accidental, not inevitable, the outcome of choices, not the product of design, contingent and therefore temporary and changeable. “When we trace the genealogy of a concept,” one distinguished exponent of the approach has argued, “we uncover the different ways it may have been used in earlier times. We thereby equip ourselves with a means of reflecting critically on how it is currently understood.”³³

The originator of this form of conceptual genealogy was Friedrich Nietzsche (1844–1900). In his On the Genealogy of Morality (1887), he pointed out that “anything in existence, having somehow come about, is continually interpreted anew, requisitioned anew, transformed and redirected to a new purpose by a power superior to it.” Nietzsche wanted to try to explain why an idea might have arisen, what purposes it once served, how power relations allowed it to endure, and what marks of its beginnings it still carried long after the original intent behind it had fallen away.³⁴ As an outstanding classicist, Nietzsche knew the importance of philology, that study of the strata of meanings laid down in complex words, and he applied its tools to the analysis of ideas and practices. His prescription was at once stringent and succinct: “All concepts in which an entire process is semiotically concentrated defy definition; only something which has no history can be defined.”³⁵ That is, the weight of history may be so densely compacted into a given concept that no effort of refinement can remove all its accreted complexities. And nothing that has a past, particularly one deep or controversial, can be specified so exactly that its meaning can be agreed once and for all.

Civil war was not one of Nietzsche’s examples, but it easily could have been. (After all, his Genealogy of Morality bore the subtitle “Eine Streitschrift”: a polemic or, literally, “conflict writing.”) Only by ignoring the multiple histories of civil war would it be possible to define it. For history shows that civil war has had no stable identity or agreed definition. A fundamentally political concept, it has been reinterpreted and redeployed in multiple contexts for multiple purposes throughout the centuries. It may look descriptive, but it is firmly normative, expressing values and interpretations more than any stable identity.

Civil war is an example of what philosophers term an essentially contested concept, so called because their deployment “inevitably involves endless disputes about their proper uses on the part of their users.” This occurs because there is so much to be gained—and so much can be lost—from the application of the concept to particular cases and because, as with other contested concepts—art, democracy, and justice, for instance—the use implies a value judgment. Is that object a work of art? Is this political system democratic? Is your procedure just? Anyone who uses these terms should have some inkling of being in for a potential fight over the prestige they carry.³⁶ At the same time, the user should also be advised that any use of such concepts “must be understood historically, as a phase in an inherited and unending intellectual task,” and that “their conflicting interpretation” is “limited by the inheritance from the past” but “never preclude[s] the possibility, and indeed the necessity, of future debate.”³⁷

In this light, the most useful critical reflection on conceptions of civil war would trace their history over a long stretch of time, centuries beyond the horizon of 1989 or 1945. Yet this approach runs counter to most current research on civil wars, dominated as it has been by disciplines that typically impose a much narrower chronological focus. After the end of the Cold War, there was a “boom in the study of civil war” among professional social scientists.³⁸ Economists who study underdevelopment, especially in Africa, isolated civil war as one of its main causes. The phenomenon has also drawn students of international relations who have seen their traditional subject of wars between states disappearing before after very eyes. And the rise of apparently ethnic conflict after 1989 excited interest in the various causes of civil strife in regions across the world from the Balkans to the Horn of Africa.³⁹ Social scientists often study only those conflicts that have taken place since World War II, when one of their standard databases, the Conflict Data Program at Sweden’s Uppsala University, begins.⁴⁰ Some extend their horizons further with the help of the vast databases forming the Correlates of War Project (founded at the University of Michigan and now at Pennsylvania State University), which goes back to 1816.⁴¹ But few have examined civil wars in comparative, long-range perspective over more than the past two centuries.⁴²

As for historians, they have not helped. They—I should say, we—have tended to study particular conflicts: the English Civil Wars, the American Civil War, the Spanish Civil War. We have rarely treated civil war as a serial phenomenon, across time and around the world. Instead, we have preferred the rich reconstruction of historical particularity over what clarity might be produced by revealing underlying patterns or models.⁴³ By no coincidence, most professional historians were content, until recently, to undertake quite sharply focused studies on time frames approximating a natural life span: rarely more than a century, often a few decades or even years. Lately, however, many have been returning to the historical big picture, the long-range view that had been out of fashion, not infrequently aiming to uncover the origins of some of the most pressing problems of our time—climate change, inequality, the crisis of global governance—which lie decades or centuries in the past.⁴⁴ A longer perspective, history’s traditional perspective, is essential if we are to see just what has been at stake, and what still remains at issue, in civil wars over the past two thousand years.

I have called this book a “history in ideas” to distinguish it from a long-established strain of intellectual history known as the “history of ideas.”⁴⁵ The latter reconstructed the biographies of big concepts—nature; Romanticism; the great chain of being—across the ages, as if the ideas themselves were somehow alive and had an existence independent of those who deployed them. But in time, the sense that ideas inhabited some Platonic sphere, far above and beyond the mundane world of human life, came to discredit the history of ideas among more rigorous intellectual historians, to the impoverishment of historical understanding of important concepts. Only recently have they—again, I should say “we”—regained the courage to construct more subtle and more complex histories in ideas over broader periods, with notions like happiness and genius, toleration and common sense, sovereignty and democracy, among others, now emerging again as central topics of study.⁴⁶ This book joins these new histories by investigating a key idea in Western, and global, argument in its multiple historical contexts. The point of origin it proposes is quite particularly Rome, not any earlier setting, such as Greece. Not all roads lead from Rome in the formation of modern political vocabulary, but a great many do. Among them are some of the most enduring ideas in the contemporary lexicon, including liberty, empire, property, rights—and civil war.⁴⁷

The “ideas” that lend this kind of history its structure are not disembodied entities, making intermittent entries into the terrestrial world from idealism’s heavenly realm, but rather focal points of arguments shaped and debated episodically across time, each instance being consciously—or at least provably—connected with both earlier and later ones. Even amid changing assumptions, such “ideas” are linked through time by a common name. They also remain connected by the freight of meanings accumulated from their dialogue with the past and, occasionally, with the future. Civil war is a prime candidate for such a history in ideas.

*

My history of arguments about civil war over the past two thousand years is purposefully more symptomatic than systematic. It is not meant as a complete history, or even a comprehensive intellectual history, of civil wars across time and space. A truly all-encompassing work, in multiple volumes written by many historians, collecting accounts of every conflict in world history that contemporaries or later observers thought was a civil war, is certainly imaginable. What is less conceivable is that anyone would want to read such an encyclopedic work.⁴⁸ To hold the reader’s attention, my focus is more precisely trained. I treat three major moments, successively Mediterranean, European, and global, over the longue durée of civil war to illustrate its genesis, its transformations, and its contemporary applications: the first in ancient Rome, the second in early modern Europe, and the third since the middle of the nineteenth century. Other histories of civil war can and should be written. This one nonetheless represents the first attempt to portray its metamorphoses over two millennia.

Treating such a vast expanse of time constrains my coverage of space. In all of the world’s major cultures, there are, of course, histories of violence within particular communities, at least four such traditions of which I am aware, and no doubt others of which I am not. The first is the Greek tradition of stasis—meaning literally “standing” or “taking a stand,” with its associations of “faction,” discord, and internal dissension.⁴⁹ I touch upon it in the first chapter, if only to explain why I give a second tradition, the Roman formulation “civil war” (bellum civile), greater prominence. In English, French, Italian, Spanish, German, Irish, Russian, and many other languages, the words for my subject are direct calques of the Roman one, or nearly so: “civil war,” guerre civile, guerra civile, guerra civil, Bürgerkrieg, Cogadh Cathartha, гражданская война(grazhdanskaya voyna). The Russian phrase comes from the German; the German phrase translates literally a term found in the Romance languages and in English. We need not assume that they all represent exactly the same concept to see that they all have two elements in common. The root of each is the word for citizen: a “civil” war is literally a “citizens’ war” or war among fellow citizens. And the original term for citizen lying behind them all is the Latin noun civis, from which the adjective “civil”—in Latin, civilis—derives, along with such weighty words as “civility” and “civilization.”

The third tradition is the Arabic, in which the term fitna—meaning, variously, anarchy, discord, division, and schism, particularly the fundamental doctrinal schism within Islam between Sunnis and Shi’as—carries some of the same connotations as its equivalent in the Roman tradition.⁵⁰And, lastly, there are Chinese conceptions of “internal war,” or nei zhan (), which can also be found in Japanese (naisen, ).⁵¹ To my knowledge, no attempt has been made to reconstruct these traditions over the long term; any comparison with them would therefore be impossible for the time being. It will, however, be part of my argument that Western conceptions of civil war are the ones that have shaped global debates through adoption by international organizations like the United Nations and by global communities of lawyers, scholars, and activists in the twentieth and twenty-first centuries.

Tracing the legacies of Roman conceptions of civil war across the following centuries, my argument identifies three important turning points in the meaning of the term. The first, in the late eighteenth century, came at the moment when contemporaries needed to distinguish civil war from another category of violent and transformative political upheaval: revolution. The second, in the mid-nineteenth century, occurred when the first attempts were made to pin down a legal meaning of civil war, an effort made, not coincidentally, during the conflict widely known, at least in the United States, as the American Civil War of 1861–65. And the third came during the late phases of the Cold War, when social scientists decided to define the term to help them analyze conflicts all around the world during an era of proxy wars and decolonization. Our confusion about the meaning and application of civil war to contemporary conflicts is the product of this long and layered history. But only with the help of history, I argue, can we understand just why its meaning remains so controversial today.

At least until the nineteenth century, and the great historical watershed marked by the U.S. Civil War, civil wars were understood as cumulative phenomena whose succession gave a shape—though hardly a comforting one—to the past and whose avoidance might yet be an achievement of the future. The experience was typically refracted by history and memory, through the record of past civil wars, in distant times and far-flung places, and through fears that the civil wars in one’s own country’s history might repeat themselves. We have no other way to approach such fears except through history if we want to understand what the victims of civil war anticipate returning. And the best means of tackling this history is through language. As we will see, civil war is such a contested phenomenon because it carries such a weight from the past and can only be discussed in words that are endlessly arguable. Conflict over its meaning, as much as the meaning of the conflict, are prime subjects for long-range historical treatment.

To tell this story, I have broken the book into three parts, each with two chapters.

The first part, “Roads from Rome,” traces changing conceptions of civil war chronologically over six hundred years from the first century B.C.E. to the fifth century C.E. During this period, I argue, Roman debates decisively shaped conceptions about civil war: about its genesis, about its normative definition, about how to recognize its outward signs, and about the likelihood of its recurrence. Thereafter, all roads would lead from Rome and not, I argue, further back from Athens and the world of Thucydides, where conflict within the community was understood very differently. The Roman heritage itself contained many different explanations of civil war and transmitted various competing narratives of its place in Roman history.

As I show in the second part, “Early Modern Crossroads,” in Europe between the sixteenth and the eighteenth centuries, those explanations and narratives derived from Rome provided the repertoire from which European thinkers drew their own conceptions of civil war. Since the Enlightenment, however, two conceptual clusters, regarding civil war and revolution, would drift apart from each other and even be set in deliberate opposition, with quite distinct moral and political implications: the first deemed backward looking, destructive, and regressive; the second, future oriented, fertile, and progressive. Successful civil wars would thus be “rebranded” as revolutions, while revolutionaries would deny they had been engaged in civil wars.⁵² But matters are never so simple; as we shall see, the two categories would continue to overlap and interpenetrate well into the twentieth century.

The book’s third part, “Paths to the Present,” traces the conceptual heritage of civil war from the era of the U.S. Civil War to our own time. The nineteenth century’s great contribution to this history was the attempt to ameliorate the severity of civil war by bringing it under the domain of law. Civilizing civil war remains an objective for the international legal community right down to our own time; the roots of its concern, and the tensions civil war presented within what we now call international humanitarian law, are the subject of the final chapter of this book, which traces developments as civil war goes global over the course of the twentieth century. At this time, the frontiers of the community beset with “civil” wars expand beyond the physical boundaries of state and empire to encompass the whole world. That expansion may be traced to various strains of cosmopolitan thought, which had long suggested that all wars, being among humans, were civil wars.⁵³ Yet the impulse is at odds with another twentieth-century effort, by social scientists beginning in the Cold War, to bring conceptual clarity to the study of civil war—a doomed enterprise, as we shall see.

As I argue in the conclusion, “Civil Wars of Words,” past definitions and conceptions of civil war persist to this day in the intellectual DNA of international organizations, journalistic organs, and scholarly discussions. Hence much of our own confusion about what is, and what is not, a civil war. The sedimentary conceptual history going back to the Roman republic has only grown more complex and more perplexing since the modern languages of law and social sciences have added layers of their own. I suggest in conclusion that the contested pasts of civil war will continue to generate multiple futures. How the knowledge of history equips us to face those futures may have consequences for tens of thousands, even millions, of people—often the most vulnerable and unfortunate—across the globe. To see why, we must first head back more than two millennia into the past, to observe the invention of civil war in republican Rome.