20 March 2011 Last updated at 09:29 ET

Libya: Aims unclear as military campaign starts

By Jonathan Marcus BBC diplomatic correspondent

After a rolling start, with French aircraft firing the first shots, this operation to enforce UN Security Council Resolution 1973 is unfolding in a familiar way.

The initial aim was to degrade and destroy Libya's integrated air defence system, largely centred in the western part of the country around Tripoli.

Land attack cruise missiles were fired from US warships and submarines out in the Mediterranean.

A British Trafalgar class submarine was involved as well.

So too were Royal Air Force Tornado GR4 fast jets.

They flew the round trip from their base in Britain to launch Storm Shadow missiles against Libyan air defences. Storm Shadow is a long-range stand-off missile that can be launched well out of range of enemy air defences.

US B-2 Stealth Bombers were also employed, dropping some 40 bombs on a Libyan airfield.

All this has put the conditions in place for the establishment of the no-fly zone.

Indeed, in Washington, the top US military commander, Admiral Mike Mullen, Chairman of the Joint Chiefs of Staff, has announced that the no-fly zone is now in place, though there may still be additional work to be done.

Civilian protection

But the dismantling of Libyan air defences also affords coalition aircraft greater freedom for their other missions - because the most urgent task demanded by the UN Security Council resolution is to protect civilians from attack by Libyan government forces.

The strikes by French jets on Libyan tanks on Saturday, outside Benghazi, were just a taster. Reports suggest that more extensive strikes against Col Gaddafi's troops have been taking place since.

This comes after reports of continuing offensive operations by Libyan government forces, especially around Misrata.

Having breached the UN Security Council resolution, Col Gaddafi's armed forces, or at least the most potent elements of them - his tanks and heavy artillery - now appear to be the main focus of attack.

His goal seems to be to get his advance elements into the rebel-held cities as fast as possible to make the targeting of these forces more difficult from the air.

That will create some problems for coalition planners, given the emphasis upon avoiding civilian casualties. But these forces - especially outside Benghazi - are at the end of long supply lines and very vulnerable to attack.

'Regime change'

We know how this operation started. One can predict how it is likely to unfold over the next few days. But how will it end? Put the question a different way: we know the tactical goals, but what is the overall strategic purpose?

UN Security Council Resolution 1973 sets out a clear aim: a ceasefire and an end to attacks by pro-Gaddafi forces on civilians and population centres.

It does not explicitly call for regime change as such, though it gives broad military latitude in terms of operations to protect civilians.

In this light, some might argue that Col Gaddafi and his generals, who sit at the top of the Libyan military command chain, might potentially be considered as targets.

But that is not necessarily a view that everyone in the coalition would agree with.

Political question

How far are the coalition forces willing to go? They will have carefully drafted rules of engagement but the question is really political and not military.

One possible outcome is the defeat of Col Gaddafi's forces and their withdrawal from rebel-held cities, leading to a kind of uneasy stalemate.

In the shadow of coalition air power, Col Gaddafi would not be able to mount offensive operations of his own. But the rebels would not have the capacity to challenge his hold on much of the western part of the country.

This would not be an attractive outcome for Washington, London or Paris. In each of these capitals, leaders have insisted that Col Gaddafi must go.

"Libyans must be able to choose their own destiny," as French President Nicolas Sarkozy put it.