John Rentoul: Iraq is a tragedy, but Blair's global goals will live on - and he will be vindicated

"The Iraq war is not an argument to be won or lost; it's a tragedy." In search of what posterity may make of Tony Blair's record in foreign affairs, I was struck by these words in one of the better first drafts of history, The Assassins' Gate, by the American journalist George Packer.

Not that the pro-war argument has been lost. As long as the Iraqis continue to say that their appalling suffering is worth it to get rid of Saddam Hussein, it cannot be. But the war has undoubtedly been a tragedy, and not just because it unleashed a new form of murderousness on the Iraqi people in place of the old.

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Blair's role has been tragic in the classical sense: that of a good man brought down by a flaw. In his case, hubris. As Correlli Barnett argues today, although he draws a different conclusion from it, Blair was led on to Iraq by the unexpected and - he was told - impossible success of his campaign of high moral statesmanship to defend the Muslims of Kosovo.

The Iraq war is a tragedy, above all, because of the damage it is inflicting on that cause of liberal interventionism, which triumphed so completely in the Balkans. It is hard to imagine Britain or America deploying pre-emptive military force against dangerous tyrants for some time. Hard, but not impossible, although it may require a little distance from Blair as Prime Minister to achieve the necessary perspective.

This is not so much because the events are too recent, but because, while Blair is still in office, "Iraq" has come to mean less a real, troubled country and more a four-letter symbol for "everything that's wrong with Tony Blair".

As soon as he has gone, a more balanced judgement of British foreign policy over the past decade may be possible. But one historian cannot wait, and has already offered a superb analysis that strips away many of the myths that have attached themselves to Blair's conduct of Iraq policy. Professor Peter Hennessy may be surprised to find his work cited in defence of Blair, because he is one of the Prime Minister's fiercest critics in these matters.

Yet the chapter on Suez in his sparkling history of Britain in the 1950s, Having It So Good, should be required reading for anyone tempted to draw parallels between Iraq and Suez.

The two are so completely different as to be polar opposites. As Hennessy writes, Anthony Eden pursued his aims of taking back the canal and forcing the fall of President Nasser of Egypt "in the teeth of attempts to divert or warn him off by President Eisenhower, his two law officers, one Chief of Staff... the Joint Intelligence Committee and the Treasury". Blair's Iraq policy, on the other hand, was pursued with the explicit support of all their 2003 equivalents.

The most damning feature of Eden's conduct was his attempt to deceive his Cabinet and the US, and finally his uttering, twice, an unadorned lie to the House of Commons.

Blair was, of course, guilty of none of these crimes, and was cleared by four inquiries and one general election. But because the occupation of Iraq has gone so badly, the case for liberal interventionism has been tainted. Yet there are grounds for measured optimism, after Blair has gone and taken the "static" with him, as he put it.

It should be remembered that the origins of an "ethical foreign policy", in its most recent phase, lay in the very same activist public opinion that so took against the Iraq war. It was American public opinion that forced President Bill Clinton to intervene in Haiti, in response to television reporting of atrocities. US policy in Bosnia was toughened in the same way.

Blair was pre-eminent among those who learned the lesson of appeasement in the Balkans. He became the most articulate exponent of a new way of doing foreign policy: harnessing the humanitarian instincts of domestic Western opinion to a new definition of the national interest, that our security is enhanced by getting tough with dictators. Only the rhetoric of standing up to a dictator is superficially similar to the time of Suez.

The Suez operation was an attempt to defend a British economic interest and a symbol of Empire. Blair redefined the national interest to mean the collective security of regions and the world and the defence of universal human rights. Thus Sierra Leone was the prologue, and Kosovo, where Blair pushed a reluctant Clinton into threatening the use of ground forces, the first act in the tragedy that unfolded in Iraq.

What has happened in Iraq has made military intervention more unlikely elsewhere, to the grateful relief of the odious regime in Khartoum, to take just one example, but it has not destroyed the new model of geopolitics. Since Iraq, Blair has helped mobilise the same forces of public opinion throughout the rich world behind his objectives for Africa and climate change.

The potential of that mobilisation is illustrated by one astonishing fact. If the Gleneagles promises were met in full, Live8 would have raised 1,200 times as much money for Africa as Live Aid did.

After Blair goes, the idea of a humanitarian, interventionist foreign policy will revive.

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