According to archeological evidence dating long before recorded history, formerly peaceful neighbors first resorted to warfare to protect their resources and place in the world; since then there have been many other motivations. Even religions that set theoretical limits on violence sanction and justify war’s necessity. More contemporary peace movements are often associated with the pursuit of human rights.
Questions of war and peace have dominated politics and philosophy since the dawn of civilization; conquest and resistance have shaped major eras of global development. But while war and peace are from one perspective inseparable twins—two sides of the same coin—the histories of war and peace have not been so symmetrical. History has often been written about war; “peace studies,” on the other hand, are a modern academic invention. (And note which term comes first in this article’s heading.) This asymmetry points to a fundamental question about war and peace: which condition, war or peace, is “normal” and which the aberration? While a historian’s answer might be that both are “normal” as aspects of the past, the question remains current because it implicates debates about human nature and, often, social and political policy. In other words, how one views the origins of war affects how one sees the possibility or advisability of trying to end war. This article will sketch an overview of the historical origins of war, of the major stages in the history of war, and of the landmarks in the less-studied history of peace.
Getting at the origins of war historically is, of course, a difficult task, and controversy surrounds all attempts at providing an answer. Even defining war proves difficult, as what counts as war is built into many interpretations of the evidence. Since written records do not take us to a time before war, historians must depend on archaeology and anthropology for evidence. Anthropological approaches have often involved studying isolated hunter-gatherer peoples living much as our ancestors did thousands of years ago. The Yanamamo of the Amazon basin are a famous case. The very high levels of interpersonal (especially intergender) and intertribal violence that characterize Yanamamo culture have often been taken as evidence that a proclivity for warfare is built into human nature. But recent reinterpretations of the original field studies in light of the broader colonial history of South America have called this reading into question. Far from being isolated, the Yanamamo have been directly and indirectly affected by neighboring (and often more complex) societies for centuries—societies which themselves practiced organized warfare, exported weapons, and in general contaminated the supposedly pristine experiment provided by the Yanamamo, or indeed by any other simple society that managed to survive into the twentieth century. And for every study of a violent tribe, there seems to be a counterexample of a study of a group living peacefully. The anthropological record, at least based on studies of living peoples, is therefore problematic.
The archaeological record poses its own problems, however, because it is far from complete. But the outlines of an answer are beginning to emerge. Skeletal remains of Homo erectus, the widespread ancestor of modern humans, have been gathered from sites across Eurasia dating from between 2 million and 100,000 years ago, and skeletons of Homo sapiens, the modern human species, from between 150,000 and 10,000 years ago have been found around the world. Of these several thousand skeletons, very few bear any unambiguous signs of human-inflicted violence, and those that do are isolated cases. In short, if we define war as organized human violence against other humans, as opposed to the odd murder, there is no evidence for it before about 8000 bce. A site in northern Iraq from around that date is the earliest of a type that becomes increasingly common later: a mass burial of several hundred skeletons showing clear signs of the impact of human weaponry. At roughly the same time, unambiguous fortifications also begin to appear in the same part of the world. The evidence spreads from this point of origin and also appears independently later in other places such as northern China.
What conditions characterize the places and times where warfare springs into existence? Not surprisingly, given the times and places involved, the conditions are associated with the emergence of agriculture. A rising population in especially fertile areas and rich hunting grounds began to put pressure on those resources. Nevertheless, populations in such areas, even before full-scale agriculture, became less nomadic, staking claims to territorially defined settlements, a trend reinforced by farming. In addition to putting pressure on resources, the rising population—in terms of both absolute numbers and the density of settlements—led to the rise of increasingly defined social hierarchies and mechanisms of community governance. Even if such developments arose to deal with questions of intracommunity dispute resolution and economic redistribution, they provided the means for a more organized and effective communal response to outside threats, especially in terms of centralized decision making. Finally, in the first case in northern Iraq and in several later cases where war making arose apparently independently, there appears to have been a severe environmental crisis that triggered the move to military conflict by creating an especially great strain on established resource levels. The result: formerly peaceful neighboring peoples resorted to organized violence against each other to protect their place in the world.
Once the resort to arms had taken place, several additional dynamics reinforced the tendency for warfare to spread rapidly beyond its points of origin, and indeed beyond places where the initial conditions held. For one, it was a successful technique, at least from the perspective of the early winners, who were of course the ones best placed to exploit the new way of life. But perhaps even more important then and thereafter was the interaction of warfare with social class and political leadership. The interests of social elites in hierarchical societies naturally diverged from the interests of the mass of the people, and warfare proved more beneficial to the elites than to the farmers, because the elites were more likely to specialize in the bearing of arms (so becoming warrior elites) and thus to garner the most in terms of glory and riches from waging war.
And as the most intense form of crisis that societies now faced, warfare made strong leadership all the more crucial. Tribal leaders, chiefs, or kings knew this and therefore favored war as policy more than the interests of their society as a whole would have. To paraphrase the sociologist Charles Tilly’s famous maxim about states, war made leaders and leaders made war. Finally, once there were war-making powers on the political map, any society in contact with them had to adopt the new mode of organization or risk conquest and extermination. Avoiding warfare was no longer an option, and war became a constant in human history, complete with fortifications, arms races, and wide-ranging social and cultural effects.
How societies made and make war is probably the central question in military history. The question has often been answered in narrow terms of strategy and tactics—the “art of war” and its supposedly universal principles. Technological determinism—the view that available weaponry shaped crucially (and perhaps exclusively) the ways of making war—also has a long historiographical tradition. But modern military history (as well as some ancient writing on war) tends to take a broader view of the question, analyzing the social and cultural parameters that shape war making in particular societies. This is not to deny that the fundamental constraints of economics and technology do not shape warfare—the largest historical patterns certainly can be constructed around such factors—but rather that how different societies make use of technology depends on their preexisting social and cultural characteristics. It is the combination of social organization and technology, in fact, that marks the first two stages of the history of war (“types” might be more accurate than “stages,” because the two existed concurrently and often in symbiosis).
In early sedentary societies, the social division of elites and commoners proved fundamental to military organization, though different states managed the division in different ways. Though masses of conscript infantry might constitute the numerical bulk of a polity’s army, a spearhead of warriors who were elite both by training and social status usually made up the most effective and sometimes the only real fighting force. The dominance of elites was reinforced through differential distribution of the best military technology, which meant in the first instance metal weapons, first of bronze and later of iron. A second technology, the domesticated horse, allowed elite warriors mounted on chariots to thoroughly dominate ancient battlefields. In time, chariots gave way to riding, but the superior social position of the cavalryman remained, marked by the height from which troopers looked down on foot soldiers and the cost of their mounts.
In later ages, the dominance of often-mounted elites usually survived socially and politically even when the massed infantry assumed central importance on the battlefield. Dominant infantry forces were not the product of technology, but again of social and political conditions. Cohesion is the key to infantry effectiveness, and it emerged in two ways. In certain circumstances, communal service, exemplified by the phalanxes of the Greek city-states, bound foot soldiers together. More often, the emergence of a strong state allowed rulers to raise and train large infantry forces, imposing cohesion from above: this is the model of imperial Rome and China. Variations of state strength, elite dominance, and social structure account for most of the different forms taken by armies from classical times and well into the second millennium ce.
But a second model of social and political organization coexisted with the sedentary elite-commons model from early on, and regularly bested the latter’s many variations in combat. Domestication of the horse (and probably the invention of the chariot as well as riding) was in fact a product of the Central Asian steppes, the vast grasslands stretching from the northwestern borders of China into the Hungarian plain. Too dry for agriculture, the steppes instead supported a population of nomadic herders. Hardened by constant competition for grazing lands and inured by their lifestyle to constant campaigning, when mounted on horses and armed with short but powerful compound bows, steppe peoples made fierce and formidable fighters, unconstrained by the need to coddle a class of dependent farmers and unspoiled by the niceties of sedentary life. The mobility and firepower of a large force of steppe warriors was hard to beat tactically.
What they often lacked, however, was political cohesion, as herding provided too little surplus on which to build stable social hierarchies and state structures, and so many steppe forces remained small. Paradoxically, nomad coalitions and protostates grew strongest in proximity to rich and powerful sedentary states, as nomadic leaders used sedentary goods obtained in trading, raiding, and conquest to build and maintain support. The eastern steppe, connected to the west by a narrow corridor between deserts and facing the often-powerful Chinese state, most often generated such coalitions, and movement on the steppe tended therefore to flow from east to west.
Nomadic conquests and alliances regularly affected the sedentary societies near the steppes, at times replacing or invigorating the ruling class and at times spreading destruction, and often serving as a conduit for the movement of goods and ideas. There were other nomadic frontiers: in Arabia, a more static tribal land that erupted only once, though decisively under Muhammad that one time; to the north of the central Mexican civilizations; in the grasslands south of the Sahara; and in a fragmented “inner frontier” in India. All were sources of military manpower and political instability, but the Asian steppes had the biggest impact.
The long-term demographic trend ran against the pastoralists and in favor of the agriculturalists, however, and after 1500 ce two further developments first reduced and finally eliminated the independent power of the steppe peoples. First was the shift of Eurasian trade routes towards seaborne commerce, a tendency that accelerated rapidly after the age of Vasco da Gama and Christopher Columbus, and that much reduced the importance of the steppes as an east-west link. Second was the spread of gunpowder technology, which in combination with spreading fortifications effectively countered the firepower and mobility that were the nomads’ greatest weapons.
An age of gunpowder weapons extending from roughly 1400 to 1800 ce is a convenient label for the next stage in the history of warfare, but the causal significance of firearms is the subject of much scholarly debate, centered around the related concepts of a “military revolution” in western Europe and the creation of “gunpowder empires” in much of Eurasia.
Again, basic variations in state strength, elite power, and social structure, as well as (increasingly) economic resources, shaped the differences in armed forces in this age, and no area could claim a significant advantage in military effectiveness until perhaps the last half of the eighteenth century, when European methods of drill, organization, recruitment, and logistics began to move somewhat ahead of the pack. But even that advantage was still limited by technologies of transport and communication that prevented the projection of significant levels of force much beyond Europe itself. Only at sea was the European combination of ships and cannon dominant before the nineteenth century.
With the coming of the Industrial Revolution, though, warfare entered a new age, as did every other area of human endeavor. While technology was central to this transformation, it was not specific military technologies that were crucial to the transformation of warfare and the emergence of true European dominance globally in the late nineteenth century, though ironclad steamships and machine guns, among other inventions, certainly played important roles. Rather, it was the vastly increased productive and transport capacities generated by industry that, through two centuries of constant innovation and improvement, brought to war the same character that it brought to the economy, politics, and culture: mass.
Mass production of weapons and supplies supported mass conscript armies, inspired by the mass politics of nationalism that had first appeared in the armies of the French Revolution and Napoleon. Mass destruction in two world wars and in the potential for “Mutually Assured Destruction” brought about by nuclear arsenals resulted. “Total War” recognized ideologically the practical effect of weapons systems that reached under water, into the air, and beyond into space: the potential to erase any distinction between the frontline and the home front. War itself had become a global phenomenon.
One reaction to the potential for global destruction made possible by modern military technology has been the decentralization of warfare. Even during the Cold War, most of the hot wars were fought by proxies for the great powers on one side or both. Since the collapse of bipolarity in 1989, decentralization has increased, with a majority of armed conflicts occurring in civil and guerrilla wars below the level of state-to-state war, including the emergence of global terrorism. Conventional wars seem likely, when involving great powers, to be waged only when the odds in favor of an easy victory are seen to be high, as in the two wars the United States has fought in Iraq; civil conflicts ensure that peacekeeping, too, will continue to occupy the soldiers of rich nations.
I know not with what weapons World War III will be fought, but World War IV will be fought with sticks and stones.Albert Einstein (1879–1955)
The other reaction to the real and potential destructiveness of modern war has been the emergence, since the mid-nineteenth century, of organized peace movements and mass protests against state-led violence. Believing that Mutually Assured Destruction is indeed a mad concept for international relations, opponents of nuclear weapons, in particular, often call for an end to all war.
The dialectic between war and peace long predates modern peace movements, of course. The emergence of war stimulated thinking about war, about peace, and about the desirability of either or both and about how peace was to be achieved.
Attitudes to war in ancient philosophy rarely invoke true pacifism, the belief that war is so evil that it should be avoided at all costs. In some warrior-dominated cultures, indeed, warfare was glorified; seeking peace would have removed all hope for glory and obviated one of the ways in which men (always men, for the history of warfare is highly gendered) gave meaning to their lives. Homer’s Iliad provides a clear example of this outlook, though the Odyssey is more balanced, and both recognize the human costs of war. The Indian philosophical tradition raised the elements of such an outlook to the level of high philosophy. The Bhagavad Gita, the central story of the epic Mahabharata, a sacred text of Hinduism, explains the concepts of law, duty, and cosmic order in terms of a warrior’s dilemma about killing his relatives in a looming battle, with the god Vishnu ultimately showing that killing is a warrior’s sacred obligation.
Other classical traditions, while perhaps less nonchalant about individual deaths, recognize war as an evil necessary to the maintenance of order (both internal and external) and required of good rulers and men in the face of threats to both order and freedom or independence. Greek and Roman writers and Chinese theorists of war such as Sunzi share this outlook, which is perhaps simply a concomitant of a secular, state-centered view of the world. For these thinkers, peace was preferable, but war had benefits, including the possibility of ensuring a more secure peace.
Another strain of ancient thought, exemplified by the Hebrew and Persian traditions, sanctioned war even less problematically as part of a universal god’s plan for the world and his chosen people. Both of these traditions influenced the salvation religions of Christianity and Islam, whose attitudes towards war and peace are complicated. Although often portrayed as a pacifist religion in its early days, Christianity in effect accepted war as soon as it accepted the existence of the state in the form of the Roman Empire, and pacifism was from the start a minority voice in the new religion. Early Christian thinkers emphasized the condemnation of war implicit in classical views but ultimately saw its necessity for order. When Christianity emerged after Constantine as the state religion, it therefore made a relatively easy transition to sanctioning warfare led by Christian rulers. Saint Augustine had worked out the main tenets of a Christian theory of just war by around 400 ce. This put limits on the proper conduct of war, but questioned neither its necessity nor its justness within those limits. By the twelfth century, a “just war” theory had accommodated the crusades, and holy war became a part of the Western Christian tradition.
Islam was born in war, and gave birth to a Muslim theory of just war that closely resembled the Christian version. The complication was that the mainstream Islamic tradition looked back to the desert past for models, and so had much more difficulty than Christianity in sanctioning the existence of the state. Since the state was vital to the prosecution of war, just or not, Muslim polities sometimes had more practical difficulty than Christian ones in sanctioning warfare, despite accepting it in theory.
The other major salvation religion, Mahayana Buddhism, has much less to say about war in explicit terms. Unlike Christianity, which came to prominence with Constantine’s military victory under the sign of the cross, Buddhism spread in the wake of the Mauryan emperor Asoka’s conversion in the third century bce, prompted by the horrors of his conquest of Kalinga, and so did contain a strong pacifist tendency. Yet Buddhist states, such as Tibet, and Buddhist warrior classes, such as the Bushido of Japan, both managed to reconcile religion and warfare, and it is perhaps more accurate to say that Buddhism encourages individual quietism, politically, rather than state pacifism. In sum, the effect of the salvation religions on warfare was mostly to put theoretical limits on the conduct of war, but within those limits to sanction and justify warfare. Peace remained an ideal more preached than practiced.
In practice, limits on warfare were more likely to emerge from particular cultural practices than from overarching religious systems. Most cultures since warfare began have imposed limits on what was and was not acceptable, both in declaring war and in prosecuting it. Rules might govern the treatment of noncombatants and the ransoming of prisoners versus killing them; convention (as well as logistics based on weather and the rhythms of agriculture) might limit campaigning seasons to certain times of year. Certain weapons or ways of fighting might be taboo, quite literally. Ritual penance often served as an obligatory aftermath of killing in war. While often connected to or interpreted within a framework of religion (including the salvation religions), such limits tended to be localized and displayed the malleability of custom and tradition.
Many of the most destructive wars in history resulted from the breakdown of such norms of warfare, either because of “cheating” by an internal player in the cultural system or, more often, because of the intrusion into the system of an external invader who did not know or play by the rules. Warfare that crossed lines of culture, in other words, tended to be bloodier than intracultural warfare, whether the lines of culture were drawn along linguistic, religious, ethnic, or class lines. Whether it occurred in the warfare of Greek city-states in the wake of the Persian invasion, in the European conquest of the Americas, or in the eruption of terrorism into New York City in 2001, the breakdown of an unstated but pervasive set of rules of war has usually stimulated both the most vehement calls for further war and the most impassioned pleas for peace—from Aristophanes’ Lysistrata to Bartolomeo de las Casas’s arguments in favor of los Indios to modern antiwar movements.
Terrorism is seen to violate norms that have acquired the force of international law, and the formalization of ritual limits on warfare, not just in law but in regulated systems of diplomacy, has also served at times to mitigate the effects of warfare. The nomad-sedentary frontier was a frequent site of both breakdowns of warrior convention and the construction of diplomatic ties that created new, broader cultures of acceptable war. While the inherent instability of the steppes often rendered such efforts impermanent, longer-lasting state-based systems of international diplomacy and understanding have perhaps worked to greater effect, and have produced in the twentieth century mechanisms such as the U.N. aimed at creating a global culture of peace rather than war.
The rise of modern peace movements as an aspect of mass politics and in reaction to the destructiveness of modern war has often been associated with other modern political movements aimed at expanding human rights generally. Jane Addams, best known as the founder of Hull House and for her efforts for women’s suffrage, also worked for world peace; Gandhi used nonviolent resistance against British imperialism and worked for peace; and Martin Luther King Jr. adopted Gandhi’s tactics to work both for civil rights and against U.S. involvement in Vietnam. While the work of individuals and even groups in promoting peace may seem unrealistically idealistic against an ongoing backdrop of civil wars, terrorism, and rogue nuclear powers and in the wake of the bloodiest century in human history, there are trends that seem more hopeful.
Political scientists like to point out that no two democracies have ever gone to war with each other (the Civil War between the United States of America and the Confederate States of America forming a controversial exception), and the world at the turn of the millennium is more democratic than ever before. The economists’ version is that no two countries with McDonald’s have gone to war with each other (although NATO did bomb Belgrade); perhaps increasing global interdependence through economic ties tends to mitigate warfare. On the other hand, environmental crises played a role in the origins of war, and they may play a role in its continuation in the twenty-first century. What is certain is that questions of war, peace, and human rights are now global concerns.
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