Nato has started a military operation which has placed its military and political credibility firmly on the line.

The use of Nato's air power is being hampered by the very poor weather it is facing over Yugoslavia. Urgent efforts are underway to bring in aircraft that can deliver weapons whatever the weather.

There is also growing talk about deploying more anti-armour weapons, maybe even Apache attack helicopters. Poor visibility is a critical factor given the strictness of Nato's rules of engagement. It wants to avoid civilian casualties as far as is humanly possible.

Yugoslav defence breaking down

But all the evidence is that the Alliance offensive is having an impact. Yugoslavia's integrated air defence system has suffered significant damage.

Barracks and headquarters in Kosovo itself have been extensively hit. What the weather does is to slow down Nato's impact and it should be remembered that the effect of an air campaign is cumulative anyway. Nato believes that it has done real damage to the supply depots, ammunition and fuel stores supporting Yugoslav troops and special police in Kosovo.

German soldiers have been involved in the first action since WWII

This is the first time that modern precision-guided weapons have been used in such an extensive operation in a European theatre-of-operations.

Public expectations about the effectiveness of air power are to a large extent based on the experience of the Gulf War. But Kosovo, even in the early spring-time is not Kuwait or Iraq. Indeed it is often forgotten that the weather too played a factor in the early stages of the Gulf War air campaign.

Political credibility doubts

Thus there is no doubt that, given time, Nato can inflict serious damage on the Yugoslav forces. But perhaps the greatest problems for Nato are not its military credibility but its political standing.

Nato has refashioned itself for the post Cold War world as an exporter of peace and security beyond its own frontiers. The Alliance is soon to hold its 50th birthday party - an elaborate summit meeting in Washington at the end of April.

It does not want the celebrations to be over-shadowed by a failure in Kosovo. This is in part why Nato countries tried so hard to give diplomacy a chance. It was only when the Rambouillet and Paris talks failed that Nato decided it had to act.