Can France achieve its goals in Mali?
From the outset, there has been an improvised aspect to the French intervention in Mali - Operation Serval, as the French have dubbed it - and for good reason.
Events were never supposed to unfold in this way.
But with separatist rebels and Islamist forces heading rapidly southwards towards the capital, Bamako, and with the Malian army crumbling in their path (the scale of the Malian forces collapse is only now becoming apparent), the French President Francois Hollande was compelled to make a rapid decision.
The choice appeared simple - to intervene or to stand by and see the Islamists triumph.
France chose to act, initially with air power and special forces to try to stabilise the military situation on the ground.
Mali is a curiously shaped country, its borders determined by French colonial administrators. It resembles a large hourglass leaning at an angle, with an arid, desert north and more fertile savannah in the south.
Tuareg separatists and Islamist militants linked to Al-Qaeda in the Islamic Mahgreb (AQIM) have taken control in the north. The initial battles have seen the French, along with remnants of the Malian army, struggling to halt the advance of the rebel and Islamist forces at the narrow waist of the hourglass.
This battle is still under way. French military sources have indicated that the Islamists are better trained and better armed than they had initially expected.
In some ways, the Mali crisis is the second act to the drama in Libya that saw rebel forces, aided in large part by French and British air power, oust Col Muammar Gaddafi.
The Libyan adventure of the then French President Nicolas Sarkozy is coming back to haunt his Socialist successor.
Libya's collapse opened up many of its arms depots to local militants. Many of those fighting in Mali are hardened, experienced fighters who had sold their services to the Gaddafi regime.
The French have halted the Islamists' advance on the eastern side of Mali's waist, but in the west, the fighting has been tougher.
The Islamists counter-attacked, pushing further south and taking the small town of Diabaly. Securing and stabilising this line along the central and narrowest part of the country is France's first military goal. But what then?
President Hollande has talked about protecting the capital Bamako - it presumably is no longer under threat - but also about restoring Mali's territorial integrity.
If this means securing the vast north of the country - an area the size of France and Belgium put together - then this will be a major undertaking. It will require significant preparation and significant military assets.
Change of plans
This whole turn of events was unexpected, though it seems curious that French and European Union military planners appear to have expected rebel forces and AQIM in northern Mali to wait until their preparations were ready before venturing into combat.
Planning was under way to bring together a West African peace force and to prepare for an EU-led training mission for Mali's own armed forces.
After several months, this force would have perhaps been ready to move northwards. The goal was to have African boots doing the soldiering on the ground, with the French and possibly others largely in a supporting role.
But the southward advance of the rebel and Islamist forces and the precipitate collapse of the Malian army changed all this.
France still hopes to make this an African operation. The timetable for the assembly of a West African peace force under Nigerian command has been dramatically speeded up.
European efforts to rebuild and re-equip the Malian army are also going to have to be rethought. The disparate West African force will be larger than originally planned, but how effective it might be in mounting offensive operations into northern Mali is uncertain.
That is a polite way of saying that its offensive capability may be limited. In the vast, arid lands of the north, even most Western armies with all their modern technology might struggle to find small bands of rebel and Islamist forces who can simply disappear into the landscape.
Offensive operations will still rely upon outside support for air power, intelligence and logistics.
With France having played the initial leading role, how will its chain of command be integrated with that of the West African force? Who will command whom? Is France willing to continue to bear some of the burden of ground operations, and if not, can its broader strategic goals be realised?
But beyond the military details, the essential political and regional problems remain. The political crisis in Mali preceded the Islamists' advance. A military coup in Bamako indeed created the opportunity for Tuareg separatists in the north and their erstwhile Islamist allies to seize control.
They have now fallen out, with the Islamists in the ascendant. Some experts believe this might provide the political opportunity to grapple towards a solution.
Mali's stability may depend upon some kind of autonomy arrangement for the Tuareg north. But that will require a stable and effective government in Bamako itself.
Mali's difficulties are equally part of a wider regional crisis extending across the Sahel. This involves a complex set of problems - poverty, drought, political instability and corruption - with Islamist extremists eager to make capital wherever they can.
The fear that really prompted French intervention and that guaranteed it wide-spread support was the nightmare that a vast area like northern Mali could turn into ungoverned space providing a sanctuary for AQIM. The violent attack on a gas facility in Algeria throwing such fears into stark relief.