Behind the facade of unanimity which NATO leaders still like to present, there is genuine worry both about the conduct of the war and the conditions which may be attached to its termination. At stake is no longer just the fate of the Albanian nation, but also the reputation of the alliance and its main political leaders.
The alliance's original mistakes in starting the Balkan offensive are by now well documented: an assumption that Slobodan Milo sevic would cave in within days, no pre-planning for the predictable humanitarian disaster and no thought about what should be done if the air campaign turned out to be ineffective. Less documented, but probably just as important, are Mr Milosevic's own miscalculations. He assumed that NATO would never go into action and that if it did, the alliance would be unable to sustain a long campaign. The Yugoslav president also genuinely believed that Russia would jump to his aid and that a peace deal which preserved his control over Kosovo would be concluded. The story of the last two months is, essentially, one of trying to cover up these fundamental strategic errors committed by both sides.
Confronted by massive air attacks, Mr Milosevic hastened the expulsion of ethnic Albanians, partly because he understood that this was his best chance to eliminate a troublesome minority population and partly because he believed that, faced with a humanitarian disaster, public opinion in the West would stop supporting the war.
However, NATO was not deflected. Concern for the plight of the refugees was never allowed to overshadow the conduct of the war and public support for the operation hardened in the West. Approximately 1,000 aircraft now operate above Yugoslavia against more than just military targets. Any cool military analysis would indicate that the alliance is bound to win this war, sooner or later. So why are NATO leaders so uneasy? Essentially, because they are stuck in a war of attrition, in which the political cost to the West increases all the time.
The Yugoslav military has always been trained to fight against overwhelming odds. During the Cold War the threat to Yugoslavia came from the Soviet Union, while today it comes from NATO. But the strategy of the country's military has remained constant. With no hope of winning, Belgrade's generals have been taught to hide their equipment and bide their time, in the hope that no enemy would be prepared to pay the casualties involved in invading Yugoslavia.
The strategy has worked better than NATO would care to admit. Because the Yugoslav military never aimed to win, it was not demoralised when confronted by NATO's military might. Western intelligence reports suggest that no more than 6 per cent of the recruits in the Yugoslav armed forces have defected. A network of fortified tunnels and pre-positioned military dumps throughout the country have made NATO's air operation more difficult.
The preservation of Yugoslavia's air defence system has forced NATO's aircraft to fly at high altitude, where it is less accurate. And an abundance of shoulder-held missiles has precluded action from the Apache helicopters which the US originally deployed in the region to smash Yugoslav military formations at close quarters.
The only way NATO could have succeeded in inflicting massive blows on its enemy was, paradoxically, by threatening a ground offensive. If Mr Milosevic was convinced that an invasion of his country was imminent, he would have been forced to deploy his troops. The tanks taken out of storage would have been easy targets for NATO, and the backbone of the Yugoslav military would have been broken.
For a while, it appeared that this was precisely what NATO governments were contemplating - a steady build-up of US, British and French troops proceeded throughout the region. But then NATO struck the inevitable obstacle of US reticence about putting its own soldiers in harm's way.
In order to persuade Washington, Tony Blair, who led the argument for a ground offensive, talked about an operation against a Yugoslav military which was already weakened by the air strikes and therefore unable to put up much of an opposition. Western troops would be expected to enter into what Mr Blair imaginatively called a "semi-permissive environment" - not with the agreement with the Yugoslavs, but not with their active opposition either.
Yet the US administration remained deeply divided. The Chiefs of Staff, Pentagon and the National Security Council adamantly rejected Mr Blair's scenario. The military, they argued, should plan for the worst eventuality, which means that it should enter Kosovo prepared to fight a long and arduous battle. The State Department was, predictably, for Mr Blair's proposition.
Such divisions are normal in Washington, and they can only be sorted out by the President. Yet Mr Clinton refused to make a decision. Military planners on both sides of the Atlantic need at least six weeks to put together a serious ground offensive. More importantly, if they do not complete these preparations before the end of this month, it would be difficult to envisage finishing a ground war and allowing the Kosovo refugees to return before the onset of the harsh Balkan winter. By refusing to make a decision, Mr Clinton has virtually scuppered a ground option altogether.
This basic fact was not lost on Mr Milosevic.
Theoretically, the air campaign could continue forever. But NATO knows that this is not an option either. As civilian casualties intensify and bombs continue to go astray, support for the operation will evaporate in the West.
So, the rush to find a peace deal is now on. The snag is that the Russians, who are crucial to these peace negotiations, now see no need to pull NATO's chestnuts out of the fire. They are prepared to persuade Mr Milosevic to accept the introduction of an international force into Kosovo. But they are not prepared to accept that NATO should lead this force, or that Kosovo should become independent.
And the Chinese, who opposed NATO's operation but remained fairly silent on the search for a peaceful solution, are now actively supporting the Russian position. The aim of these two permanent members of the UN Security Council is to make clear that, if a deal is reached, the alliance will not be able to claim it as its own victory.
President Milosevic is a mere bystander in this greater political game. But he is eager to complicate it further. On an almost daily basis he puts forward new peace proposals. The latest offer this weekend was a partial and unilateral withdrawal of his forces from Kosovo.
Mr Milosevic knows perfectly well that these offers are likely to be rejected by NATO. Yet he assumes that their cumulative effect would be to sap Western cohesion. The more the debate about a deal becomes a technical matter of how many peacekeepers should be introduced into Kosovo and under which flag, the bigger the chances are that the fighting would stop while Mr Milosevic is still in possession of Kosovo. And, if one Yugoslav soldier remains on the ground in the province, the refugees will not return. This is precisely the end-game which Mr Milosevic is playing for.
No doubt NATO will proclaim victory whatever peace deal is ultimately reached. But immediately after the fighting stops the recriminations within the alliance over this operation will emerge into the open. And the biggest political losers will be Mr Clinton and Mr Blair, who raced ahead proclaiming high principles.
The breakdown of the political truce in London between the Labour government and its Conservative opposition this weekend is merely the foretaste of the reckoning which is now inevitable.
Jonathan Eyal is Director of Studies at the Royal United Services Institute in London.