But when the allies did finally decide to launch an aerial assault on Kosovo a month ago, they must, presumably, have believed that the matter would have been dealt with by the time the red carpets were unrolled in Washington. It was only a few days ago that they started to lower the bar of expectations socially and militarily. The war was not yet won; it was frozen in a semi-permanent condition of being won, and won, above all, for Nato itself. "We are fundamentally there [in Kosovo] because the alliance will not have meaning in the 21st century if it permits the slaughter of innocence on its doorstep," said Bill Clinton, opening the Nato commemorative ceremony on Friday. The conflict proved that "our alliance has principles, and the courage to act upon them", said Javier Solana, Nato Secretary General.
The line that has been repeatedly reaffirmed by spokesman after spokesman in the past few days, as Nato has gathered to celebrate its half-centenary, is: "carry on bombing. The strategy is working. The air campaign will work. Everything is going according to plan".
"We are going to win, no question about that," said Mr Solana. "We are winning," said General Wesley Clark, the Supreme Allied Commander in Europe. "He [Mr Milosevic] is losing. And he knows it." There have been hints of other arguments from the European members of Nato, with Tony Blair arriving to present a more aggressive message that included a greater stress on ground troops. It has not gone anywhere, because the Americans want to maintain the idea that they are prevailing and that the strategy chosen here is unflawed.
There is little sign of an endgame developing, nor of serious thinking about how to resolve the situation. The proposals brought back by the Russian mediator Viktor Chernomyrdin were held at arm's length. There will be no military coup de main to break the deadlock; the much-vaunted Apache helicopters are still days away from operation. Nato still lacks air superiority at low levels, which is limiting what it can do.
The crisis feels very distant from Washington. It is, like Iraq, a television war, far away. Over the past few days, the Nato summit has brought with it a strange, hallucinatory sniff of crisis that is very far from the real thing, but at least a reminder that something is happening. The night is filled with the wail of police cars, not of air raid sirens, and helicopters shake the roofs of houses in downtown Washington, in a parody of Belgrade's agony.
But it has not brought any closer focus on the problems of the war. Most of the delegations have been on best behaviour, simply parroting the line that everything is for the best in the best of all possible wars. This is a progressive war, a war for virtue and principle, a precision war, they have emphasised, one that exemplifies the best side of the longest- surviving alliance since the League of Delos in the fifth century BC. But in fact, of course, the action marks a sharp break in alliance history. Nato was founded as a defensive alliance, not an offensive organisation. Its aim was to protect Western Europe from Soviet attack, not as a crusading group to protect human rights. It is acting against a country that borders only one member state, Hungary, and threatens none.
It was vital for the US that, after the Cold War, Nato should be seen to have meaning and almost before the Berlin Wall was down, serious efforts were being made to convert it into something else. After the abortive effort at the 1990 London summit to create a "political" Nato, an alliance that was about jaw-jaw rather than war-war, those efforts returned to a redefinition of a military Nato: an organisation that could project force outside its own borders, supporting US interests beyond the scrubby heathland of the North European plain. The swords that had been beaten into ploughshares would be beaten back into swords. The aerial assault on Bosnia in 1995 was the first instalment of that; Kosovo, however, has provided the first proper task for the emerging new security structures, even before the alliance has had a much of chance to complete its thinking. "Instead of doing it on paper, you're doing it in real life," said one Western diplomat.
That is why it is, for the politicians and the military bureaucrats, so vital that they win, and be seen to win, this war. If they do not then an organisation that has had so much energy, so much money and so many hours of planning poured into it will start to crumble. And for the four- star generals and the political-military establishment, if you ask them whether that matters more than Kosovo itself, they would probably answer: of course. "Nato has an obligation to be successful," said Jamie Shea, the alliance spokesman, last week. "We cannot afford to lose this one. We have invested too much time, too much effort."
In particular, it is vital for the military bureaucrats to convince the US - its people and politicians, but especially its congressmen - that this is a functioning, successful adjunct to US national security policy and not an arm of the Eurovision song contest, an image suggested by the profusion of the flags and the silly signing ceremony on Friday, where each head of state made a short speech. Vast energy has been spent on making this occasion (at least) look polished.
These days Washington is not that comfortable with grand international occasions, or indeed with international affairs in general. To be fair, Kosovo is a complex issue, but once there would have been congressmen and senators ready to grapple with it. Not so today. There are very few people on Capitol Hill of either party with any great calibre when it comes to foreign policy. Seats on the Senate Foreign Relations Committee, once highly fought over, are now much easier to get, and the committee itself is led by the ageing and reactionary Jesse Helms. Many of the faces on the television chat shows commenting on the crisis have been retreads from previous administrations and Congresses. The right-wingers who swept in during the 1990s were largely elected to ignore foreign policy. Many came to office without passports. The White House needs to keep these people happy; and the Europeans, who want at all costs to keep US troops in Europe and a strong link across the Atlantic, have to agree.
So far, nobody in the Washington establishment has seriously contested either the handling of the war in Kosovo, or Nato itself. As long as the conflict clatters on, with no American casualties and no dramatic consequences for the US, it is unlikely that they will. The US has a short attention span. After all, who, now, can remember why America and Britain battered Baghdad in Operation Desert Fox last December? Who remembers the endless briefings about how Saddam's regime was on its last legs, its key facilities destroyed, its main supporters crippled? But the bombs still fall on Iraq in the long, undeclared war that rages on over the Northern and Southern "No-Fly Zones", despite the lack of any effect. In the same way, the allies continue to pour high explosive on Serbia.
The summit could, conceivably, have been the occasion for asking the difficult questions, about Nato in general and Kosovo in particular, but that never looked very likely, and once the war began, it became impossible. Both Canada and Germany wanted to question Nato's nuclear doctrine; now, that chance has slid away. It is simply too delicate a moment, because what is really at stake - as it has been, in the minds of the politicians since the inception of the Balkan wars - is Nato and Western unity.
In some ways, what matters to the White House and the Europeans at the moment is just the image of a war under way. Virtually any end to the conflict now - whether a successful one for Nato, with alliance troops and money used to clear up the mess, or an unsuccessful one, with bombing clearly proved unsustainable, or most likely something in between - will complicate matters. It is easier for Nato leaders, especially at the alliance's real home ground, Washington DC, to press on regardless, rather than ask any difficult questions. At the moment they are by their own accounts winning, every day, even when nothing whatsoever can be adduced to prove that.