analysisBy Paul Melly
Having decided on a muscular emergency intervention to stop jihadist groups from sweeping south to Mali's capital Bamako, France's President Hollande's administration has opted for decisive force. It hopes to make a fundamental breakthrough and lay the basis for Malian and allied West African forces to restore the authority of the central government across the north.
Sixty French armoured vehicles have arrived in Bamako, and more troops have been announced. Altogether 2,500 French soldiers could soon be on the ground, backed up by air power. Other European countries are helping out, with British transport planes flying in more French equipment and soldiers, Denmark and Belgium are also assisting, and Germany is expected to play a significant role in retraining the Malian army.
Indeed, even before the panic provoked by last week's launch of a jihadist pincer move towards Mopti and Sévaré, the gateway to the south, France was already pushing hard for the rapid despatch of up to 400 EU military training personnel. The UK was a keen supporter of Paris in making the case for this training mission.
This massive effort comes at huge cost. A French helicopter pilot has already been killed; and there is clearly a risk of further casualties, to say nothing of the enhanced terrorist threat to French lives elsewhere. And jihadists still hold French civilians hostage in the Sahel. The financial impact will also be felt in Paris as high-tech warfare is expensive, with one estimate putting the cost of operating a Rafale jet at €23,000 per hour.
Why is Europe, and France in particular, so heavily engaged?
Visiting Dakar and Kinshasa last year for his début trip south of the Sahara, President Hollande stressed that the old post-colonial days were gone. France was ready to offer support, but Africa would set the strategy and take the lead in tackling its problems.
This message was in tune with the view from Europe as a whole. But paradoxically, it is this stance that explains in part why France and fellow EU states, including the UK, were ready to back the intervention plan being developed last autumn - and now respond to the crisis threat posed by the jihadist advance last week.
West Africa is Europe's near neighbour. The region's security and prosperity - or lack of it - has a direct impact on Europe.
When West Africa faces humanitarian crisis, Europe - and other partners such as the US - provide emergency assistance. When the region is unstable or in economic difficulty, illicit migration flows towards Europe are intensified. When drugs are smuggled through the Sahara they usually end up north of the Mediterranean.
Moreover, despite common outside perceptions to the contrary, West Africa has made huge progress over the past 15 years, riding out crises in individual countries. Between 2004 and 2008, economic growth in the eight West African franc zone states averaged 3.7% a year, while in Nigeria it was 7% and Ghana 6.5%. Drought brought a slowdown for many countries in 2011, but last year brought a strong rebound almost everywhere, and the trend is set to continue.
Meanwhile, country by country, democracy and good governance are being slowly entrenched. And the Economic Community of West African States (ECOWAS), encompassing all states in the region, has stood out from many other regions of the developing world in its commitment to these principles of political reform, even if individual member states sometimes fall short.
If the jihadists breakthrough into southern Mali, demonstrating that in the space of 12 months an entire state could be effectively wrecked by small bands of - largely foreign - extremists, would have been a devastating reverse for West Africa as a whole.
The political development, human rights gains, economic growth and investment confidence of recent years would have been placed in jeopardy. The consequences would be felt in every country from Senegal to Nigeria.
Of course, a jihadist state in Mali would also enhance international terrorist risks. But actually this is the secondary threat. The greater risk, both for the region and for Europe, would have been the unravelling of the stability and progress that West Africa has painstakingly constructed - not without setbacks - over the past two decades.
That is what is at stake.
President Hollande's decision to respond to the appeal of Mali's President Dioncounda Traoré with such a forceful military intervention is not in conflict with his declared support for African-led reform. Quite the contrary, it is the consequence of that stance.
A jihadist victory across Mali, and the instability and conflict that this would provoke, would represent a threat to stability and economic growth across West Africa as a whole. The defence of a peaceful, developing and secure West Africa is a fundamental interest for Europe.
Paul Melly is Associate Fellow in the Africa Programme at Chatham House.