What happens next, even the most bemedalled television studio strategist will hesitate to guess. In terms of military capability, national will and possible unintended consequences, few recent conflicts are so hard to read. Few are so short of obvious parallels. Generals, proverbially, are always tempted to refight the last war. But in the case of Kosovo, which war?
Kosovo, it may safely be said, is not Vietnam. For whereas Vietnam was populated by Vietnamese, less than 10 per cent of Kosovo's 2 million inhabitants are Serb. And unlike Hanoi, Belgrade has shown no stomach to endure aerial bombardment "for a generation" to secure its goals. But then again, Kosovo and Serbia are not Iraq - a bare, flat land where targets are hard to hide and the enemy's capacity for self- defence (pace the apocalyptic warnings of Tony Blair and George Robertson, the Secretary of State for Defence) is derisory.
In terms of terrain, this looming Balkan war will be like Balkan wars before it, fought across hills, forests and scattered population centres. For Andrew Brooks of the International Institute for Strategic Studies, it is in some ways "a big Switzerland. The forces are dispersed, they've dug a lot of holes in mountains, there's a tradition of fighting for soil, they can't be taken out in one fell swoop".
This is the tough-as-nails Serbia of legend, which President Milosevic does nothing to discourage. Nato has crushing air superiority, more than 400 top-of-the-line Western aircraft, against 80 Soviet-built planes, mostly ageing MiG-21s. However, "while you can destroy air defence centres", says Mr Brooks, "Belgrade has mobile radar units, and a lot of people with surface-to-air missiles".
Then there is the matter of targets. It is assumed that in a first phase, Nato will go for communications and air defence sites and swiftly thereafter ammunition depots. But eight years ago, an even larger onslaught failed to knock out may of Iraq's scud missile units. And if Yugoslav armour on the ground is directly targeted, the lesson of Chechnya and similar conflicts is that infantry and artillery dispersed in rough country can stand up to a massive amount of air bombardment. Assuming, of course, they have the will.
For some believe that a replay of Bosnia 1995 awaits. For all the bravado now, a little serious bombing four years ago and Mr Milosevic went meekly to Dayton, where a peace was reached. But will the Serbs crack so easily this time? Bosnia, after all, was a sovereign independent state. Kosovo is, legally, a part of the republic of Serbia. Will it really be surrendered so easily?
And Nato is operating under constraints its opponents need not observe. Presumably special force operatives are already among the men on the ground, able to pinpoint targets for the attacking aircraft. Even so, Nato governments will insist their pilots hit the right targets with the smallest possible "collateral damage" - the unintended killing of innocent civilians - and debacles such as last summer's destruction of the pharmaceuticals factory in Sudan.
Analysts say Belgrade may already have shifted ammunition depots into urban areas, making cruise missiles harder to use. Pinpoint bombs are still best launched from planes with human beings at the controls. If so, many experts predict, Nato losses will be inevitable, with uncertain political consequences back home.
Small wonder Nato leaders pray that a small dose of bombing does the trick - that Mr Milosevic then convinces hardliners that he has done all he can, and that the Kosovo game is up. But suppose it doesn't. Suppose rather that this most cynical of politicians, whose overriding goal is survival, calculates that any surrender spells his own political (conceivably even physical) demise.
So he fights on. His air defences bring down allied aircraft, perhaps with the loss of their pilots. At this point, Nato will have lost control of events. The tidal logic of war takes over. The air strikes are widened to embrace infrastructure targets such as roads, rail links and power stations. The message is now addressed to the Serbian people as a whole: this is what happens when your leader defies Nato.
But in the process the alliance becomes ever more the de facto air force of the Kosovo Liberation Army, finessed into providing cover for the insurgents to launch a land offensive. Its neutrality would be a sham. And, unlike Bosnia four years ago, all this without the backing of the United Nations - indeed in the teeth of the unalloyed opposition of two of the five veto- holding permanent members of the Security Council, one of them Serbia's traditional ally, Russia.
At this point nerves in London and Paris would be at snapping point. But what if Mr Milosevic still fails to see the light, while his forces, quite possibly resupplied by Russia, retain enough firepower to savage the ethnic Albanians? The last, worst scenario becomes reality. Nato is faced with the choice of ignominiously calling it quits, widening the bombing further and thus rallying Serbs behind their leader - or doing what it has vowed it will never do, sending ground troops into a "non- permissive" environment: in plain English, an invasion of sovereign Yugoslavia and the launch of a land war against Belgrade.
Yesterday, Paddy Ashdown warned the West to plan for precisely this. Logically, he is correct, for the lesson of Bosnia is that if the West wants to impose a Balkan peace where both sides have to make do with less than all they want - in this case an autonomous Kosovo that is still part of Serbia - a protectorate policed by Nato peacekeepers is the only way to achieve it. But logic can have unpalatable conclusions. If they get it wrong, the Liberal Democrat leader warns, the big powers will be "on the threshold of a major ground conflict on the mainland of Europe... closer than at any time in the second half of the 20th century". Major ground conflict in Europe? At this point Kosovo's parallels come from the first, not the second, half of the century. Far-fetched they may be, but they are also truly terrifying.Reuse content