It was clear what it had left behind: a failure. The alliance has in effect conceded what had become all to clear in the past week: its efforts to stop Serbia from cleansing Kosovo of ethnic Albanians, and crushing the KLA's insurgency there, have failed. It is far from clear where it goes from here, but a drift towards a ground conflict looks increasingly inevitable.
For the past two weeks, Nato has relied on aircraft and missiles alone to achieve its goal. This draws on a long-standing American military preference for air power, it minimises allied casualties and it means that Nato can stand at a distance from the conflict. So far the option of sending in allied forces has not been seriously raised.
It would involve a force of more than 100,000, would take weeks to deploy and would cause serious political problems. Any force would have to be approved by Congress, still a tough task. The strategy of an air-only assault has, however had grave weaknesses.
The weather has meant that aircraft have been unable to get to their targets, the flow of refugees has shifted the political and ethical goalposts, and criticism has mounted in Europe and America. Slobodan Milosevic controls the ground and it is increasingly clear that so far, he has prevailed.
The US Department of Defense in effect conceded the point yesterday, when it said that, in perhaps as little as five days, most Kosovo Albanians would have left the province. Serb forces have been damaged, but are still operating at will. The KLA is very close to defeat. The Rambouillet peace agreement, which was supposed to be the point of the exercise, is a dead letter. It is time to pick up and start again.
The inquest into how this happened is already flaring in the US. The Washington Post reported yesterday that the heads of the US services had warned that such an eventuality was a possibility - though they all signed off on the operation. At a very brief press conference, President Bill Clinton passed the tough questions about this on to William Cohen, his Secretary of Defense, and then slid off into the wings. Mr Cohen's future in the administration may not be very bright.
From both London and Washington, however, there were tightly co-ordinated attempts to sound decisive and look forward rather than back.
"These people need to go back to Kosovo ... and we will make sure that happens," said Tony Blair.
"The ethnic cleansing of Kosovo cannot stand as a permanent event," said Mr Clinton.
For the moment, the priority is being put on the refugees: on caring for them when they arrive, allowing them to move as swiftly as possible to Nato-protected "sanctuaries," and rehousing some abroad.
But if the refugees are to go home, then the next part is the more difficult.
For the time being - partly out of the lack of a better alternative - the bombing will continue, and escalate.
"We are prepared to sustain this plan for the long haul," said Mr Clinton. "Our plan is to persist until we prevail."
The US is sending in Apache helicopters, which will enable it to attack Serb ground forces, and missile systems, which will be used to hit Serb anti-aircraft sites. They will be accompanied by US soldiers and armoured fighting vehicles.
There are two ways in which the conflict could develop. The first is that Mr Milosevic - now that he has essentially achieved his objective - could try to broker a deal that leaves him in control of Kosovo, with some concessions made to allow some refugees back into a rump Kosovo, rather like the Palestinian territories occupied by Israel. Though the bombing can do grave damage to him, he has the upper hand since he occupies the land and, as yet, Nato does not.
The US tried to make it very clear that this will not wash. It wants an end to the fighting, a withdrawal of Serb forces, a Nato force in Kosovo and self-government for the Kosovo Albanians. "We have made clear what our four objectives are and we're not going to allow him to try to pre- empt those objectives with some phony peace deal in the coming days," said the State Department spokesman Jamie Rubin.
The other way the present fiasco can be resolved is by taking the refugees back in. The new US helicopters and missiles can be used to batter Serb forces further. There is already a substantial Nato force in Macedonia, and more troops are on the way.
The US has denied it will allow its ground forces massed on Kosovo's southern border to be used to "force the door" for a refugee return, and has said they will enter Kosovo only as part of a peace-keeping force after a peace deal.
But the logic of the allied position, and the deployment of the new weapons systems, points increasingly towards ground forces.
If Mr Milosevic does not accept the refugees' return under Nato terms, and if Serb forces do not collapse and are not militarily defeated by air power alone, then the choice facing the West may be very stark: accept a fait accompli, or fight its way into Serbia.
That will be hard to do with aircraft and helicopters alone.Reuse content