As the European Union marks the 50th anniversary of one of its basic treaties, the most successful continuing exercise in large-scale regional cooperation faces a major challenge from an unexpected direction - North Africa. The conflict and French intervention raise fresh questions about Europe's ability to act as a coherent force in a complex world.

After the crisis over its common currency and ongoing dissention with wavering members, notably the United Kingdom, the European Union now must grapple with violent Islamic radicalism in North Africa. France's intervention to protect the broken government in its former colony of Mali from the advance of rebels from Al Qaeda in the Maghreb, AQIM, has opened up not only the prospect of an open-ended involvement in an uncertain conflict. After the attack on the gas facility in Algeria last week, there is prospect of a much wider struggle which British Prime Minister David Cameron warns could last for decades.

When he decided to send French troops to Mali two weeks ago, President François Hollande hoped that a strong counteroffensive on land and in the air would push back the rebels advancing on the capital of Bamako. Backing Malian troops, they could then stabilize the situation as an African multinational force moved in to help the government which has been unable to stem the southward progress of their Islamist foes from an entrenched position in the north of the country. "The intervention will be a question of weeks," Foreign Minister Laurent Fabius forecast. Latest reports from the front indicate that the combination of air attacks and the armored advance of the spearhead of the 2,000 French troops is achieving its immediate objective. But, as has become unavoidably clear since the attack in Algeria, the task reaches well beyond simply forcing the rebels, both AQIM and Taureg nomads, to give up towns they had taken and scatter into desert hideaways.

The need to evolve a stable political system in Mali is a daunting task as is the rebooting of the economy. More widely, powers from outside the region seem only now to be waking up to the danger posed by AQIM. The French action may have stopped Mali from becoming a second Somalia. But as Cameron put it at the weekend, the situation in the Sahel region of North Africa requires a response that will be "about years, even decades, rather than months" and which conjures up the specter of another Afghanistan.

For European states which are keen to disengage from Afghanistan, that is a most unwelcome prospect, bringing with it a fresh test of just what the European Union means beyond the coordination of the economies of its 27 member states. Though Britain supplied two transport planes, the initial move to shore up the Mali government militarily was almost entirely a French effort with the central EU bodies in Brussels proving tardy with anything more than rhetorical backing.

It was only 10 days after the French troops arrived and after the attack in Algeria that the European Union offered to host a meeting in Brussels on 5 February to bring together the EU, the African Union and the Economic Community of West African States, or Ecowas. EU foreign policy chief Catherine Ashton set up a "clearing house" mechanism to centralize requests for and offers of logistical support for the African-led intervention force. Known as Afism, this is to consist of 3,300 troops. Backed by the United Nations, it's expected to be largely funded by the US and Canada with the EU putting up €50 million, a quarter of the total cost.

While Washington appears to have reservations, the key country is, as so often in Europe, Germany and, in another familiar pattern, the government in Berlin is finding it hard to make up its mind. On the one hand, it expresses solidarity with France as is only to be expected in the circumstances and especially since the two countries this week celebrate the 50th anniversary of the Franco-German Friendship Treaty signed by Charles de Gaulle and Konrad Adenauer to seal the reconciliation between the two states after three wars over three-quarters of a century. The Foreign Ministry in Berlin has stressed that Germany will not "leave France alone in this difficult situation."