Wednesday, April 28, 1999 Published at 12:21 GMT 13:21 UK
Analysis: Escalating the war
Nato's campaign is set to intensify
By Defence Analyst Nick Childs
The man in charge of the Nato air campaign, General Wesley Clark, said the operation had been very effective, very destructive, but also "only a fraction of what is to come".
According to General Clark, Nato already has three times as many strike aircraft as it did at the beginning of the campaign.
And the US call-up of reservists underlines that more reinforcements are on the way.
Many of the reinforcements will be support aircraft - for example over a hundred US tanker planes.
New dimension to attacks
These "force multipliers" will enable Nato to keep more combat aircraft in the air longer, crucial to its ability to search for military targets which are often hidden or camouflaged.
Another key development will be the operational debut of the US Apache attack helicopters now based in Albania. Their role of attacking at low level will add a new dimension to Nato attacks.
Clearly, weather has been a critical factor so far. According to General Clark, on two-thirds of the days of the campaign so far, half the strike missions have had to be cancelled.
But the Alliance still believes its operations are having a visible effect on Serb operations on the ground.
It says 70 of the Yugoslav air force's main fighters have been destroyed, as well as between 25 and 40% of its larger air defence missile batteries.
And it says there are increasing reports of desertions and low morale in the Serb military.
Civilian casualties 'unavoidable'
But it remains very difficult to estimate when this kind of damage will have a tangible effect in terms of reversing the situation on the ground.
Nato has stressed the efforts it has gone to in order to minimise civilian casualties - the number of strike missions cancelled is a reflection of this.
The Alliance says that in a campaign of this scale, such incidents are unavoidable.
Already, there has been the attack on a bridge which hit a train, the attack on the refugee convoy, and an attack on a communication centre in the Kosovo capital, Pristina, where again a bomb went astray.
Weapons can go wrong
It remains a sensitive issue. For all their technical advances, sometimes weapons go wrong.
The Alliance has shown videos of attacks being aborted because a pilot is uncertain of the target, or concerned about its proximity to civilian areas. But sometimes, that is not possible.
Problems can intervene after a weapon is launched - for example cloud could suddenly obscure a target, or cause a laser-guided weapon to go out of control.
And as Nato has broadened its target list, to hit sites and installations closer to the heart of the political leadership, so that has increased the risks of civilian casualties.
Many are in residential areas. Some, like the Socialist Party headquarters in Belgrade or the Belgrade radio and television station, are - Nato insists - dual use, with direct military links.
Bridges, while they are strategic targets, are also inevitably used by civilians.
Nato will continue to hit such targets. There is, Nato officials say, no shortage of such targets, as the Serbs have built their military command structure with many back-ups.
There are, for example, over 100 road relay stations throughout the country. And it will "revisit" targets already hit, as the Serbs are trying to repair them. And it clearly it will be able to sustain public support.
'A lot left to do'
The other factor is how much more Nato will be able to target Serb forces directly involved in Kosovo. It is that element which has been most directly affected by the weather.
Nato hopes that will improve now. And it has adapted its tactics and weaponry. But so too have the Serbs, who are trying their best to hide their forces.
The alliance believes it is beginning to see cracks in Belgrade's resolve. It says it has done great damage, but also that there is a lot left to do.
But it clearly feels bolstered by the public show of determination at the Nato summit, not least the support shown by Serbia's neighbours, who were also in Washington.