There were, as Nato allies freely admitted at the start, a great many risks and uncertainties about the outcome of air attacks against Serb forces in Kosovo. But about one possible response from Belgrade there can have been very little reason for doubt.
The savagery that armed police and the Yugoslav army showed to the Albanian population in Kosovo, which prompted the Nato action in the first place, was virtually guaranteed to escalate once they met resistance from military might greater than their own. Unable to strike back at their attackers, the Yugoslav army can only unleash its heightened fury on the ethnic Albanians by stepping up its campaign of ethnic cleansing.
In his address to the American people on Thursday President Clinton spoke of stopping the Balkans from becoming a place of brutal killing and massive refugee flight. Today, officials talk about a 'humanitarian catastrophe' of unprecedented proportions in the region. Some 50,000 Kosovo Albanians are reported to be massed on the border with Albania, driven out of their homes at gunpoint. A trickle of refugees is also starting to arrive in Montenegro. The fate of those who remain can only be guessed at, but eye-witness acounts tell of paramilitaries and other irregulars killing at random, rounding up men for execution, bombing houses and burning the homes of those whose lives they spare, so that they have nothing to return to.
This is a process which has been going on to a greater or lesser degree in the former Yugoslavia for several years, and eventually something had to be done to try and bring the carnage to a halt. But Nato defence chiefs are wrong if they believe that a tyrant like President Slobodan Milosevic, the 'Butcher of the Balkans', would revert to civilised rules of behaviour following even intensive waves of strikes by cruise missiles and laser-guided bombs. The more damage is inflicted on Mr Milosevic's arsenal, the more he is likely to shift the focus of his resistance by trying to involve neighbouring states in the conflict.
Intensified Britain's announcement that it will send extra Harriers and Tornados to the theatre of operations, with the aim of hitting tanks and artillery, increases the danger to air crews, and it would take very few losses to lessen public support for an intensified campaign. Opposition will increase if days or weeks of military strikes do not appear to be having the desired effect.
While some Nato partners talk with resolve about increasing the air strikes until Mr Milosevic is tamed, others are already wavering. Italy seems unlikely to support a sustained campaign, and if there are many civilian casualties, or destruction of schools or hospitals, an already rumoured split in the ranks could become a reality.
The longer the action continues, the greater the danger of trouble spreading elsewhere, and the more condemnation of the military strikes will grow.
Limitations Not for the first time in recent years, the lesson is reinforced that military action pursued at a distance has profound and grave limitations. Even if the Nato allies succeed in destroying every piece of military hardware in Mr Milosevic's armoury, he has a brutal and seasoned war machine shooting its way through the Kosovo villages against which air attacks can have extremely limited effect.
These troops can only be contained or subdued by a force on the ground, and that has always been the inevitable conclusion to the present action. Otherwise, there is no guarantee that Mr Milosevic will capitulate, as Nato must realise, even though the Yugoslav army is hopelessly outgunned. And nothing is more certain to fuel the fires of nationalism that a small nation under attack from mightier forces.
With all opposition silenced within the country, and while Nato continues to bomb their cities, popular support for the beleaguered president will continue. And with bad visibility hampering air operations, and planes returning without bombing for fear of hitting civilians, Nato's dilemma is intensifying.
If air strikes do not drive Mr Milosevic back to the negotiating table, what can Nato do to protect the Albanians from further atrocities? Wholesale destruction of Yugoslav armaments will take weeks or months, while a campaign of terror is waged against the ethnic Albanian population, and thousands more are likely to die or be displaced.
If war criminals such as Zeljko Raznatovic and his thugs are rampaging around Kosovo, they must not be allowed to escape justice. After the conflict is over, Mr Milosevic and other leaders, military or political, who have instigated or carried out this murderous campaign must be brought to justice at the international courts.