The damage inflicted from the air to the enemy's operational capability is a necessary prerequisite to any final conflict. But it takes a lot of air power to dent a really powerful military machine. The more intense the bombing becomes, the more inevitable the risk of unintended fatalities. Harsh but true.
After three weeks of engagement, Nato is stuck in the middle of two strategies without clarity about what the endgame will look like, or how it intends to get there. There has never been a war when the generals were so hidebound by their government masters. Political reluctance to address the question of how and when ground troops will be committed means that Nato's only explanation for what it is doing - and for what went wrong this week - is incomplete.
Officially, the strategy is simply, in Robin Cook's words, "to continue until the job is finished". But it was always improbable that bombing alone would finish the job. Early optimism that any show of force would stay Milosevic's bloody hand in Kosovo proved wrong. So the raids were stepped up, targets increased in order to cause maximum damage. This makes sense as a preparation for sending in ground troops. It is harder to justify if this goal has not been made clear - and indeed, is still officially denied.
Air power, for all the advances in technology, cannot tell Serb-commandeered trucks or tractors from those occupied by Kosovan refugees. As the pressure intensifies on the Serbian forces and their petrol supplies run out, they will commandeer more civilian vehicles. From the Serb point of view, there is every reason to expose fleeing refugees to Nato attack.
As both George Robertson and Robin Cook showed when they spoke with palpable strain of Wednesday's incident, just two days after civilian deaths on the bombed train, the simple mantra that the air attacks must continue because that is what we started, sounds less convincing when Nato has killed the very civilians it went to war to save.
We are uncomfortably reminded of the Catch-22 logic of the American spokesman in Vietnam who announced : "We could only save the village by destroying it." Public faith in Nato could decline sharply if its actions are seen to produce diminishing returns or to lack the clarity of a crusade. The alliance never looked so vulnerable as in its first ill-considered attempt to spin the early news of the disaster. The public in America and Europe knows that Serbia's heavy-handed propaganda is mendacious: it requires a higher standard of honesty from the alliance.
At the Brussels summit, Europe showed a united front, not least because EU countries learnt from the humiliation of Bosnia that they have nothing to gain by parting company from the Americans at a time of crisis in Europe. But there are differences of nuance which need to be addressed soon. Far from being, as his critics carped, Bill Clinton's poodle, Tony Blair has the far greater crusader's instinct and desire to move the conflict along to a conclusion. Officially, of course, there is no distinction between the British and US positions. But the view that ground troops are a necessity is acknowledged today more readily in London than Washington. The longer a decision is postponed, the more potential there is for Nato countries to develop their own ideas of how the conflict should end. Nervousness in Europe about the winnability of the war is the greatest risk to alliance unity.
In all likelihood, ground troops will be the last chapter - or rather the beginning of a whole new book. The remaining question is how they will get there, and under what circumstances. The first option is an all- out offensive, which has hitherto been deemed too risky. The second is if southern Kosovo is abandoned by the Serbs, so that Nato can move in without an offensive against Milosevic. Hence Mr Cook's prediction that there "may be circumstances in which one could envisage an international protection force going in without a formal treaty arrangement, but with no resistance on the ground". The third option is to allow the Russians a greater role. Moscow and Nato would move into Kosovo together, the Russians guaranteeing Serb security in return for partition - the option Mr Blair appeared to dismiss.
It falls to America to decide how this will end. Up to now, President Clinton's dominant consideration has been not to risk US casualties. But there is another imperative for a White House incumbent anxious to salvage the reputation of his presidency: namely to ensure he is not seen to have led America into humiliation. Unless Nato sets out what it means by victory and how it intends to achieve it, it may well be seen to have lost the war that does not speak its name.
Timetable: Day 23
Thursday 15 April
2.15pm: Nato "deeply regretted" causing civilian deaths in the convoy attack but stressed strikes against Yugoslav military targets would continue.
3pm: The US signals that the Nato air campaign could stretch into summer.
5.45pm: OSCE announces five members of KLA were killed and eight wounded in fighting along the border of Yugoslavia and Albania earlier in the day.
6pm: Four mortar bombs land in a village 20km inside northern Albania, close to Kukes.
6.20pm: Several explosions on the outskirts of the Montenegrin capital, Podgorica.
7pm: Nato warplanes hit the area around the Montenegrin coastal towns of Bar and Ulcinj, Serbian news agency Beta reported
7.45pm: Twelve new US F-16 fighters land at Aviano air base, Italy.
8.40pm: Air raid sirens sound in Belgrade.
8.55pm: Large explosion in central Novi Sad, said Tanjug news agency.
10pm: Four loud explosions in the northern Serbian town of Subotica.
10.50pm: A large fire burning in the Belgrade industrial suburb of Pancevo following two explosions, said Tanjug.
11pm: Tanjug says Pancevo's oil refinery and oil depot hit by Nato.Reuse content