Anthony Sampson: We are in danger of remembering the First World War but forgetting its lessons

Many of Britain's leaders, as well as Germany's, felt a psychological need for a war and even a bloodlust

After all the anniversaries celebrating the landings in Normandy and the victories of the Second World War, this week has commemorated a still more significant historical milestone: the 90th anniversary of the outbreak of the First World War in August 1914.

After all the anniversaries celebrating the landings in Normandy and the victories of the Second World War, this week has commemorated a still more significant historical milestone: the 90th anniversary of the outbreak of the First World War in August 1914.

The ceremony could be attended by only a handful of centenarians who took part in that war, who could recall its hardships and terrors: but it recalled a more awesome turning point than 1939 or 1944. The First World War not only took a far greater toll of British lives than the second. It also brought a much wider economic destruction: it undermined the whole system of world trade and prosperity which by the end of the war appeared to have vanished for ever.

"What an extraordinary episode in the economic progress of man that age was," wrote John Maynard Keynes, looking back on it in 1919. "The inhabitant of London could order by telephone, sipping his morning tea in bed, the various products of the whole earth." And he went on to describe how he could invest his money in new enterprises across the world, and travel freely without fear of interference.

It was a truly global marketplace, with an extraordinary freedom of trade, transport and travel. But it would never be recovered over the next decades. Nationalism and protectionism put up their obstacles between nations; Europeans moved towards the Second World War; and that war was soon followed by the Cold War which established new divisions between East and West.

It was not till the coming down of the Berlin Wall, and the collapse of the communist regimes in 1990, that the world began to open up again to produce a genuinely global marketplace, and the history of our time began to take a new shape. The 76 years since 1914 began to look (as the historian Eric Hobsbawm described them) like "the short 20th century".

In the following 14 years the global marketplace extended further and huge capital sums flowed across the world. That short century began to look more and more like an aberration from the economic progress that had stopped in 1914: a progress which - as Keynes described it - had seemed "normal, certain and permanent". And by the new millennium the more prosperous British were taking on many of the characteristics of the Edwardians a century earlier, with their luxury, complacency - and indifference to inequality.

But there was another element in British society before 1914 which has worried historians - and not just Marxist historians - in more recent decades: the preoccupation with armaments, and the need for enemies. The origins of the First World War, and the causes of the British arms race with Germany, remain hotly debated; but it was clear that many of Britain's leaders, as well as Germany's, felt a psychological need for a war, and even a bloodlust, which played a part in bringing about the eventual catastrophe.

And in later decades the more hawkish leaders still showed a need for an enemy, which could distort more rational policies. After the Second World War, cold warriors on both sides built up the dangers from the other side - often quite misleadingly, as we now know from the archives - to justify their own policies, and their jobs.

When the Cold War ended, the hawks faced a serious anticlimax. "We are going to do something terrible to you," warned Georgi Arbatov, the wily Russian expert on America, who was a member of the Central Committee of the Soviet Union, before the collapse of communist governments. "You will no longer have an enemy."

It took some years to realise how terrible that was. At first there were enough threats to world peace to keep Americans and European military forces busy: the end of the Cold War encouraged nationalist governments to wage their own wars, which demanded Western intervention - whether in the Gulf War against Saddam Hussein, or in the Kosovo war that followed the disintegration of Yugoslavia.

But the new enemies were too complicated, and too diverse, to satisfy the more hawkish spirits in the West; while the hopes of an effective world government, under the aegis of the UN, were soon dashed by rivalries and evasions. Murderous forces in Africa - whether in Somalia or Rwanda - could cause mass genocide, but they were too incomprehensible, and too unthreatening to the West, to provoke sustained interest, and intervention.

It was in this confused context that a new enemy suddenly appeared from the American skies in 2001, destroying the Twin Towers in New York with the quite unpredicted weapons of Islamist terrorism. The immediate response of President Bush was to declare war on terrorism; but the word "war", as the historian Sir Michael Howard warned, was quite inappropriate as a definition of the real challenge; and the word "crusade", which Bush at first rashly used, had dangerous implications, with its association with medieval military crusades.

The need for a straightforward enemy was all too evident in Washington, where veteran cold warriors such as Donald Rumsfeld and Dick Cheney quickly resumed their previous war mode, looking for purely military solutions as opposed to any serious outreach to face up to the causes of terrorism.

The leaders of the new American empire looked to be making the same mistakes as the old British imperialists when they came up against terrorism in the 19th century. The Americans saw the world in terms of nations which were either for them, or against them; and having failed to find or destroy their perceived enemies, al-Qa'ida and Osama bin Laden, they sought a military enemy, Saddam Hussein, who could more easily be eliminated. But the war only provoked much wider opposition, and the concentration on military solutions was increasingly discredited as they generated more recruits for global terrorism.

In retrospect, 2001 already looks like a more profound historical watershed than 1990. The world before 11 September appears like a vanished age, not only because it has become less safe, and less secure, but because the map of world trade is beginning to retreat, as it did in 1914. Whole nations in the Middle East, needed desperately by the West for their oil supplies, have become no-go areas for Western businessmen.

The triumphalism of 1990, when the opponents of international capitalism appeared to have collapsed, looks like a false dawn. We can no longer believe that the end of confrontation between superpowers will in itself bring a new era of peace; we can be much less confident that we are returning to the golden age of capitalist growth before 1914.

Looking back over those 90 years, we must remember not just the appalling suffering of the First World War, and the courage of its veterans. We must reflect on the terrible complacency and mistakes that came before it, and the lessons that should be learnt. Who are our real enemies, and who are our friends? And how do we avoid dividing the world once again, turning friends into enemies?