The invasion of Iraq marked a diplomatic revolution. For the first time since Suez, a major power - and in this case the world's most powerful military state by a very large margin - deliberately launched a war outside its traditional sphere of influence without being threatened with imminent attack. The new US policy, which implied war might be more than merely a last resort in the face of imminent danger, flew in the face of prevailing international norms.
Once war had seemed a natural part of international life. But not for many decades past. Nazism, and two world wars, have left their mark. It was, after all, fascism's unabashed militarism (and not its racism) that so shocked the world. That is why the Nazi defendants at Nuremberg faced charges of conspiring to wage aggressive war, as if they were not statesmen but criminals ganging up on the civilised ways of a peace-loving world. Whatever may be the difference between conspiring to wage aggressive war and plotting a war of "pre-emption", it is not enough to hide the fact that the national security strategy of George W Bush takes us in a new and dangerous direction.
The image of the US has been so deeply tarnished that it will take years to recover. In addition, the sight of a rampaging rogue superpower has completely transformed the position of the UN as well. Badly regarded by the Bush administration, it has thereby acquired new virtues in everyone else's eyes.
Whose bidding does the UN exist to serve? Is its prestige bolstered or diminished by having turned - in the eyes of many of its members - into the repository for an alternative, more consensual and far more desirable way of ordering the world's affairs than that posited by the Bush administration? These questions are symptomatic of the intense spotlight that now shines on that institution too.
Behind the war itself, there was little strategy but ideology aplenty. The neo-conservatives appear to have believed - and it was more an article of faith than an analysis - that toppling Saddam would automatically democratise first Iraq and then the rest of the Middle East, and that this process would facilitate a peace settlement between Israel and her Arab neighbours.
The fallacies are now self-evident, but to bring out the truly lethal consequences, we might compare the situation in the Middle East at present with that in eastern Europe. Both are zones where, after 1918, older empires collapsed and were succeeded by newly-minted nation-states. And in both, this territorial settlement was vulnerable because these nation-states did not really exist except in the wishful mind of their sponsors. Interwar Czechoslovakia, Poland and Yugoslavia were not so different in that respect from Mandatory Iraq; they were all patchworks, with substantial minority populations.
Yet nearly a century later, how differently they have turned out. In eastern Europe, ethnic cleansing wiped out many minorities, while the bitter experience of the Second World War made people aware of the fragility of regional peace. Pan-European political and legal frameworks stabilised borders and inhibited changes to them by force. Relations amongst once hostile neighbours dramatically improved.
The transition to democracy after 1989 was mostly smooth. Czechs and Slovaks divorced quietly. Even the break-up of Yugoslavia failed to trigger off a wider conflict. Everyone felt they had too much to lose and today, eastern Europe's problems are chiefly those of economic enlargement.
In the Middle East, things took another path. Right at the outset, Woodrow Wilson brought independence to Slavs but denied it to Arabs; instead, colonial rule by Europeans replaced that of the Ottomans. The main consequence of the Second World War was not the shock of experiencing total war but the creation of Israel, which destabilised the region still further. And whereas Eastern Europe fell under Soviet hegemony and thus avoided becoming a plaything of the superpowers during the Cold War, in the Middle East the American-Soviet antagonism ran through the region, as each power wrestled with the other through its proxies.
External interventions and the conflict with Israel militarised politics and undermined democracy. Even before 2003, therefore, the Middle East state system had travelled in the opposite direction to that taken by eastern Europe. But it took the invasion of Iraq to reveal how easily it could all unravel.
The EU has - for obvious reasons - not played the same kind of stabilising role in the Arab world that it has in eastern Europe. There is no carrot of membership (except possibly for Turkey), and thus no European incentive to democratise. Rather, democratisation has been introduced by the Bush administration, and rendered suspect because of this.
When one looks back to the days of the Eisenhower administration, one sees how far the US has moved from playing the role of honest broker in the Israel-Palestine conflict. Yet Washington's predicament is that while it can no longer act as an effective intermediary, neither is it powerful enough to impose peace on its own terms.
Can the European Union do more to make a difference? Yes, if it recognises how far its own security now depends upon calm beyond its borders. For decades the EU devoted itself to tackling the chief 19th-century threat to the continent - the Franco-German antagonism. This it did so successfully that the problem no longer exists. The task for a new generation of EU leaders is to show what their very considerable soft economic power can do to project an alternative route to peace.
The writer is a Professor of History at Columbia University, New YorkReuse content