Historians' fears of a major European conflict are mistaken, argues Mark Mazower. But as Mary Kaldor (right) tells Kate Worsley a new type of war is emerging

Historians shy away from optimism. We would rather be accused of pessimism than complacency. As the century ends, and brings with it the collapse of so many dreams, erstwhile believers see the gloom closing in around them: Eric Hobsbawm leaves his epic cycle of world histories on an almost despairing note: the alternative to a changed society, he warns us, "is darkness". Samuel Huntington discerns a time where "the rivalry of the superpowers is replaced by the clash of civilisations", and predicts new sources of global conflict.

But are they right? It is true that after 1989 the short-lived sense of triumph which followed the collapse of communism in the West rapidly vanished as Yugoslavia tore itself apart. One minute it seemed that a new era of tranquillity was dawning in Europe, the next that violence and conflict had returned. As old hatreds resurfaced, it was easy to see the revival of nationalism as the root of Europe's future troubles. Communist elites may have switched smoothly to new roles as nationalist figureheads, but their Western observers were not far behind them, expertly retooling their own cold war skills.

The identification of nationalism with aggression, war and instability tempted not only those suddenly nostalgic for the old certainties of a divided Europe. It also, more obscurely perhaps, provided the rationale for the European dream, highlighted after 1992 as never before, of an ever-closer union of states. This union, after all, has a clear historical function; it is designed to end any further possibility of Franco-German rivalry - a rivalry between nation-states which led to three wars in a century.

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Once the guarantee of Europe's tranquillity was seen in its very multiplicity of states; since the second world war, the tendency has rather been to see nation-states themselves as the menace. And yet: what if the premise is wrong? What if there is no likelihood of war between Europe's major powers, France and Germany in particular? What if the ghosts of the past offer a poor guide to the future, if there is no need for the federalist cure because the disease - the chaos of a continent torn apart by nationalist rivalries - has vanished?

At a time when events in Kosovo could easily spiral out of control and lead to further bloodshed, and when conflict in the Eastern Aegean is a distinct possibility, it may seem perverse to argue that war has been banished from Europe. To be sure, war has not been banished entirely, especially in the Balkans. But conflict in the Balkans will not lead to a larger European conflagration any more than did the Yugoslav wars of 1992-1995. War on the scale of the two world wars is less likely than at any time in the recent past.

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For Europe's 20th century divides sharply into two halves. Before 1950, more than 60 million people died on the continent in wars or through state-sponsored violence; by contrast, the number of those who died in such a fashion after 1950 is well under one million, even counting the war in Yugoslavia. If the nation-state is blamed for the bloodshed of the first half of the century, it should also be given some credit for the peaceful character of the second. The Common Market started out as a series of negotiations among nation-states and remained a forum for such negotiations for most of its life. Only in the mid-1980s did the federalist impulse grow, largely because of French unease at growing German strength.

Yet fear of Germany is a classic example of what happens when the past is projected into the future. Germany and Russia between them provided, it is true, liberal democracy's two greatest threats this century, but they also suffered the highest death tolls of any European countries. Germany's predominance remains the fundamental feature of the European power structure as it has done for a century, but Germany's dreams of empire are gone. Its military caste died on the eastern front. Five million war dead weigh more heavily on German minds than Hitler's triumphs, and if German companies invest today in eastern Europe it is not because they represent the vanguard of a Fourth Reich but because they are capitalists, whose capital is as vital as ever to Europe's economic health.

History seems even less likely to repeat itself with Russia. The country is smaller than at any time in the past two centuries. The need for social reconstruction and the decrepit state of the army produce nationalism and a nostalgia for communism but also make renewed empire-building unlikely. The Russian minorities who remain in the Baltic states are less of a threat to Europe than decaying nuclear warheads and unsecured military installations.

And what is true of Germany and Russia reflects a deeper sea-change. The expansionist, militarised nation-state of the first half of the century has been replaced throughout Europe by something more benign. Since the second world war cooperation has replaced competition between Europe's nation-states. They abandoned their colonies with no obvious harm to national security or prosperity; indeed, their standard of living boomed as never before. Nuclear weapons rendered much older strategic thinking obsolete and made it harder to envisage war as a part of national policy. Minorities still exist, but in far smaller numbers than before 1950: genocide, expulsion and assimilation have effectively removed the chief causes of the second world war. Europe has entered an era in which war, empire and land have come to seem much less important for national well-being than they once did. The Bosnian Serbs' obsession with land was the last atavistic cry of older ways of thinking that have died out almost everywhere else.

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Today population is declining in Europe yet this evokes none of the frenzied panic about national virility, racial purity and military preparedness that it did in the 1930s. Most of Europe is either in, or wishes to join the European Union and Nato, a situation with no historical precedent. Nation-states remain strong and cannot be willed away. Nor need they be, since they pose no threat any longer to continental peace. If peace indeed stretches before us in Europe, it is largely because those wars earlier in the century have turned nation-states from dreams into realities. On the whole the 20th century has consummated Europeans' love-affair with the nation-state and brought them what they wanted, if not in the way they wanted it. And if they now see that the sense of nation remains under challenge - from globalisation, from labour mobility and multi-culturalism - they are also being forced to realise that war offers no kind of solution to late 20th-century problems.

I would like to be more pessimistic, but I find it hard to see these past few years as anything other than what, at the end of a supremely violent century, must count as a surprisingly benign close.

Mark Mazower is reader in history at Sussex University. Dark Continent: Europe's Twentieth Century, is published by Penguin, Pounds 20.