Most people are very surprised by the claim that we live in the most peaceful period in history. Are we not flooded with media reports and images of conflicts around the world today, some of them very active and bloody, and others seemingly waiting to happen? Have the United States and its allies not been involved in a series of messy wars over the past few decades? Scholars, for their part, ask themselves, if there has indeed been a decline in belligerency, when exactly did it begin: with the end of the Cold War, in 1945, or perhaps earlier? And what exactly caused it?1 Again, most people are surprised to learn that the occurrence of war and overall mortality rate in war sharply decreased from as early as 1815 onward, especially in the developed world. The so-called Long Peace among the great powers after 1945 is more recognized, and is widely attributed to the nuclear factor, a decisive factor to be sure, which concentrated the minds of all the protagonists wonderfully, as they say about the hanging rope. The (inter-)democratic peace has been equally recognized. However, the decrease in war had been very marked even before the nuclear era, and has encompassed nondemocracies as well as democracies. In the century after 1815, wars among industrializing countries declined in their frequency to about a third of what they had been in the previous centuries, an unprecedented change. Compared to their record during the eighteenth century, Austria and Prussia, for example – neither of them a democracy – fought about a third to a quarter as much during the century after 1815. Indeed, the Long Peace after 1945, more than 70 years to date and counting, was preceded by the second longest peace ever among the modern great powers, between 1871 and 1914, 43 years in all; and by the third longest peace, between 1815 and 1854, 39 years. Thus, the three longest periods of peace by far in the modern great powers system have all occurred after 1815, with the first two taking place before the nuclear age. This striking phenomenon cannot be accidental. A decline in belligerency began from 1815, not 1945 or 1989. Clearly, one needs to explain the entire period of reduced belligerency since 1815, while also accounting for the glaring divergence from the trend: the two world wars. There is a tendency to assume that wars have declined in frequency during the past two centuries because they have become too lethal, destructive and expensive – fewer but more ruinous wars. This hypothesis barely holds, however, because relative to population and wealth wars have not become more lethal and costly than earlier in history. The wars of the nineteenth century, from 1815 to 1914 – the most peaceful century in European history – were in fact particularly light, in comparative terms. Prussia won the German Wars of Unification in short and decisive campaigns and at a remarkably low price, and yet Germany did not fight again for 43 years. True, the world wars, especially World War II, were certainly on the upper scale of the range in terms of casualties. Yet, contrary to widespread assumptions, they were far from being exceptional in history. We need to look at relative casualties, general mortality rates in wars, rather than at the aggregate created by the fact that many states participated in the world wars. For example, in the Peloponnesian War (431-403 BC) Athens is estimated to have lost between a quarter and a third of its population, more than Germany in the two world wars combined. In the first three years of the Second Punic War (218-216 BC), Rome lost some 50,000 male citizens of the ages of 17-46, out of a total of about 200,000 in these ages. This was roughly 25 percent of the military age cohorts in only three years, the same range as the Russian military casualties and higher than the German rates in World War II. Similarly, in the thirteen century the Mongol conquests inflicted on the societies of China and Russia casualties and destruction that were among the highest ever suffered during historical times. Even by the lowest estimates casualties were at least as high as, and in China almost definitely far higher than, the Soviet Union's horrific rate in World War II of about 15 percent of its population. A final example: during the Thirty Years War (1618- 1648) population loss in Germany is estimated at between a fifth and a third – either way again higher than the German casualties in the First and Second World Wars combined. People often assume that more developed military technology during modernity must mean greater lethality and destructiveness, but in fact it also means greater protective power, as with mechanized armour, mechanized speed and agility, and defensive electronic measures. Offensive and defensive advances generally rise in tandem and tend to offset each other. In addition, it is all too often forgotten that the vast majority of the many millions of non-combatants killed by Germany during World War II – Jews, Soviet prisoners of war, Soviet civilians – fell victim to intentional starvation, exposure to the elements, and mass executions rather than to any sophisticated military technology. Instances of genocide in general during the twentieth century, much as earlier in history, were carried out with the simplest of technologies, as the Rwanda genocide horrifically reminded us. Nor is it true that wars during the past two centuries have become economically more costly than they were earlier in history, again relative to overall wealth. War always involved massive economic exertion and was the single most expensive item of state spending. Both sixteenth and seventeenth centuries Spain and eighteenth century France, for example, were economically ruined by war and staggering war debts, which in the French case brought about the Revolution. Furthermore, death by starvation in premodern wars was widespread. Another strand of interpretation of the perceived decrease in warfare during recent times has posited voluntary and ideaic factors, has attributed the decline of warfare during recent times to a social 'attitude change'. Why this attitude change should have occurred at this point in history rather than any time earlier is not explained. After all, most powerful moral doctrines such as Buddhism and Christianity decried war for millennia without this having any noticeable effect. It is suggested that people have suddenly become aware that war is senseless if not crazy, devoid of any rationale. Such a view of war is widespread in today's modern and affluent world. In the discipline of international relations so-called realists, especially ‘defensive realists’, even claim with a straight face that countries have never gained from war because of the balancing effect that contain rising powers. Try this strange idea on Rome, the Aztecs or Inca, the Ottomans, the Mughals or eighteenth century Britain, to name but a few out of many examples. Or on Chinggis Khan, whose descendants constitute, according to genetic studies, 8 percent of all males in Eastern and Central Asia, evidence of staggering sexual opportunities enjoyed by his sons and grandsons whose houses ruled over that part of the world for centuries. And you should not think that only autocrats and military aristocracies profited from war, while the people were its unwilling victims. This idea was advanced during the Enlightenment and is very popular today. However, it ought to be remembered that the two most successful war-making states of classical antiquity were democratic Athens and republican Rome. And they were so successful precisely because the people of these polities benefited from war and imperial expansion, championed them, and enlisted in their cause. Half of the Athenian budget at the time of Pericles came from the tribute of the Empire which was used to build the Acropolis and pay for the huge navy, in both of which the demos was employed. We said before that in pursuit of their aims people may resort to cooperation, peaceful competition, or violent conflict. Each of these behavioral strategies is a well-designed tool interchangeably employed, depending on the particular circumstances and prospects of success. Thus, to understand the gravitation of human choices – and norms – from violent conflict towards the non-violent options of cooperation and peaceful competition one needs to understand the changing circumstances and calculus of cost-effectiveness during the past two centuries and in recent decades. So if modern war has not become more lethal and expensive, why the decline? Two main theories dominate the scene: the democratic peace and the capitalist/trade peace. But, in and of themselves they cannot be the complete answer because of the following, contradicting historical evidence: premodern democracies and republics actually did fight each other; nondemocratic great powers also shared in the general reduction in belligerency during modern times, from 1815 on, including communist powers that largely opted out of the global trade system; until the nineteenth century states tried to monopolize trade by force and bar all others out rather than share with them – think ancient Athens, medieval Venice, early modern Holland, France and Britain, and many others. What then is the cause of the decline in belligerency? Even before the middle of the nineteenth century, thinkers such as Saint-Simon, Auguste Comte, and John Stuart Mill, who were quick to note the change, realized that it was caused by the advent of the industrial-commercial revolution, the most profound transformation of human society since the Neolithic adoption of agriculture. In the first place, given explosive growth in per capita wealth, about 30 to 50-fold from the onset of the revolution to the present, the Malthusian trap has been broken. Wealth no longer constitutes a fundamentally finite quantity, when the only question is how it is divided, so wealth acquisition progressively shifted away from a zero-sum game. Secondly, the significance of trade in the economy has ballooned to entirely new dimensions precisely because of the new process of industrial growth. Greater freedom of trade has become all the more attractive in the industrial age for the simple reason that the overwhelming share of fast-growing and diversifying production has now been intended for sale in the marketplace rather than for direct consumption by the family producers themselves. During industrialization, advanced powers' foreign trade increased twice as quickly as their fast growing GDPs, so that by the beginning of the twentieth century, exports plus imports grew to around half of GDP in Britain and France, more than onethird in Germany, and around one-third in Italy and Japan. Consequently, economies are no longer overwhelmingly autarkic, having become increasingly interconnected by specialization, scale and exchange. Foreign devastation potentially depresses the entire system and is detrimental to a state's own wellbeing. What Mill discerned in the abstract in the 1840s, was repeated by Norman Angel during the first global age before World War I, and formed the cornerstone of John Maynard Keynes' criticism of the harsh reparations imposed on Germany after that war. Greater economic openness has decreased the likelihood of war also by disassociating economic access from the confines of political borders and sovereignty. It is no longer necessary to politically possess a territory in order to benefit from it. Of all these factors, commercial interdependence has attracted most of the attention in the scholarly literature. But both the escape from Malthus with rapid industrial growth and open access have been no less significant aspects of what I call the Modernization Peace. Thus, the greater the yield of competitive economic cooperation, the more counterproductive and less attractive conflict becomes. Rather than war becoming more costly, as is widely believed, it is in fact peace that has been growing more profitable. If so, why have wars continued to occur during the past two centuries, albeit at a much lower frequency? In the first place, ethnic and nationalist tensions often overrode the logic of the new economic realities, accounting for most wars in Europe between 1815 and 1945. They continue to do so today, especially in the less developed parts of the globe. Moreover, the logic of the new economic realities receded during the late nineteenth and early twentieth centuries, as the great powers resumed protectionist policies and expanded them to the undeveloped parts of the world with the New Imperialism. This development signalled that the emergent global economy might become partitioned rather than open, with each imperial domain becoming closed to everybody else, as, indeed, they eventually did in the 1930s, with the Great Depression. A snowball effect ensued, generating a runaway grab for imperial territories. For the territorially confined Germany and Japan the need to break away into imperial Lebensraum or 'co-prosperity sphere' seemed particularly pressing. Here lay the seeds of the two world wars. Furthermore, the retreat from economic liberalism in the first decades of the twentieth century spurred, and was spurred by, the rise to power of anti-liberal and anti-democratic political ideologies and regimes, incorporating a creed of violence: communism and fascism. Since 1945 the decline of major war has deepened further. Nuclear weapons have been a crucial factor in this process, but no less significant have been the institutionalization of free trade and the closely related process of rapid and sustained economic growth. The spread of liberal democracy has been equally potent. Indeed, although nonliberal and nondemocratic states also became much less belligerent during the industrial age, it is the liberal democracies that have been the most attuned to its pacifying aspects. Relying on arbitrary coercive force at home, nondemocratic countries have found it more natural to use force abroad. By contrast, liberal democratic societies are socialized to peaceful, law-mediated relations at home, and their citizens have grown to expect that the same norms be applied internationally. Living in increasingly tolerant societies, they have grown more receptive to the Other's point of view. Promoting freedom, legal equality, and political participation domestically, liberal democratic powers – though initially in possession of vast empires – have found it increasingly difficult to justify ruling over foreign peoples without their consent. And sanctifying life, liberty and human rights, they have proven to be failures in forceful repression. Furthermore, with the individual’s life and pursuit of happiness elevated above group values, sacrifice of life in war has increasingly lost legitimacy in liberal democratic societies. War retains legitimacy only under narrow and narrowing formal and practical conditions, and is generally viewed as extremely abhorrent and undesirable. Thus, modernization, most notably its liberal path, has sharply reduced the prevalence of war, as the violent option for fulfilling human desires has become much less rewarding than the peaceful option of competitive cooperation. For instance, with the much increased sexual opportunity within society, young men now are more reluctant to leave behind the pleasures of life for the rigors and chastity of the field. 'Make love, not war' was the slogan of the powerful anti-war youth campaign of the 1960s, which not accidentally coincided with a far-reaching liberalization of sexual norms. Furthermore, is societies of plenty people naturally become risk-averse. Ingelhart’s World Values Survey reflects this, as does, only a bit less seriously, Thomas Friedman’s concept of a Macdonald Peace. All these are interrelated aspects of the Modernization Peace. The fruits of these deepening trends and sensibilities have been nothing short of miraculous. The probability of war between affluent democracies has declined to a vanishing point, where they no longer even see the need to prepare for the possibility of a militarized dispute with one another. The security dilemma between neighbours – that seemingly intrinsic feature of international anarchy – no longer exists among them. This is most conspicuously the case in North America and Western Europe, the world's most modernized and liberal-democratic regions. Realists in international relations theory have never been able to explain why Holland and Belgium no longer fear in the slightest a German (or French) invasion, a historically unprecedented situation. Similarly, Canada is not at all concerned about the prospect of conquest by the United States, though people find it difficult to explain why exactly this is so. In East Asia, the most developed countries, such as Japan, South Korea, and Taiwan, do not fear war among themselves or with any of the other developed countries, though they are deeply apprehensive of being attacked by less developed neighbors, such as China or North Korea. With the collapse of the Soviet Empire and rapid economic growth coupled with democratization in Eastern Europe, East and South Asia and Latin America, the prospect of a major war within the developed world seems to have become very remote. Thus, war's geopolitical centre of gravity has shifted radically. The modernized, economically developed parts of the world have become a 'zone of peace'. War now appears to be confined to the less developed parts of the globe, the world's 'zone of war', where countries that have lagged behind in modernization and its pacifying spin-off effects occasionally still fight among themselves, as well as with developed countries.