As the size and complexity of the operation became clearer, it was evident that there will not be enough time to get everyone home before the weather once more turns for the worse.
The peacekeeping force will include 44,000 Nato troops - including 12,000 Britons, 7,000 Americans and 6,500 French - as well as 4,000 non-Nato soldiers from other European nations. There is no indication if, where, or in what strength the Russians would participate.
Until the Serbs withdraw, nothing will happen. There was no withdrawal under way yesterday. Fighting was still taking place in several areas between Serbs and the Kosovo Liberation Army (KLA). Some Nato nations want a UN Security Council resolution before they deploy, and a meeting of G8 ministers will take place later this week to prepare it.
The first stage of a peacekeeping operation would be for Serbian forces to withdraw in stages over seven days, starting from the south-west of Kosovo, moving up to the north. Enabling forces of the Nato nations would replace them as they left. "As they withdraw, Nato will come in and fill in behind them," said Ken Bacon, the Pentagon spokesman. This will be a highly complex job to choreograph.
The British and French (who are in the central and western sectors) would go in first. Highly mobile, lightly armed forces - the Parachute Regiment for Britain and the Marines for the US - would be deployed initially.
The enabling forces will de-mine their sectors, then set up communications, military headquarters and command posts, clear important infrastructure like airports, roads and bridges and prepare for the arrival of larger, more heavily-armed forces, such as elements of the US 1st Infantry Division. It will be one or two months before the whole force is present. Then they can begin the task of repairing infrastructure and preparing for refugee return.
There are at least three problems for Nato. The first is the finding, housing and feeding of internally displaced people still in Kosovo. This alone will preclude bringing back the refugees from Macedonia and Albania, who are at least under cover.
Then there is the question of the local Serb minority population. The Pentagon's expectation is that most if not all would leave for Serbia. "Many Serbs may want to leave Kosovo," said Mr Bacon, who gave little indication that the US was concerned if this resulted in a further ethnic partition.
It is not clear how their safety will be ensured if they stay, because there is also the question of the KLA. They would be demilitarised but not disarmed. Mr Bacon said: "They will be allowed to keep hunting rifles and things like that." In practice it would be impossible to disarm them without a fight which Nato clearly does not want.