Although the aims of the Nato mission against Yugoslav targets have been clearly stated, ending this operation on Nato's terms may be far from easy.

The attacks on Yugoslav air defences could continue for a number of nights until the alliance decides that it is safe enough for its war planes to switch to more extensive strikes against Yugoslav ground forces in Kosovo itself.

But while the first night of operations highlighted Nato's strategy, it also provided some hints as to the Yugoslav president Slobodan Milosevic's own thinking.

The fact that Yugoslav aircraft sought to engage Nato war planes, underlined that Mr Milosevic shows little sign of backing down in the face of this onslaught.

More interesting was the fact that few surface-to-air missiles seem to have been fired suggesting in part the effectiveness of the Nato operation, but also the probability that Mr Milosevic is husbanding these resources for a later stage in the campaign.

Nato's stated goal is the reduce the Yugoslav army's ability to attack the Albanian population of Kosovo.

This will require nothing short of a sustained attack on Yugoslav army units.

Mr Milosevic may believe that he can hunker down and absorb this punishment in the hope that outside diplomatic intervention, or a shift in the mood of Western public opinion, will bring this Nato campaign to an end.