FRANCE’S decision on January 11th to begin air strikes against Islamist rebel positions in northern Mali, designed to prevent “the establishment of a terrorist state” in the African Sahel, contained elements of both surprise and familiarity. The surprise was that François Hollande, the president, a Socialist leader not known for decisive action and untried in foreign policy, moved so swiftly to order French fighter jets and attack helicopters into action. Using warplanes based both in France and at a permanent base in nearby Chad, the French struck rebel columns advancing out of Islamist-held territory and towards Bamako, the Malian capital. Such groups, with ties to Al-Qaeda, have ruled a big chunk or the north of the country since March last year. The French government said that the weekend air strikes, part of what it is calling Operation Serval, had stopped the rebel advance, and helped Malian troops to regain control of the town of Konna; one French helicopter pilot was killed, as well as a dozen Malian soldiers. On the third day of air attacks, the French struck deeper into Islamist-held territory, targeting training camps and logistics centres, according to Jean-Yves Le Drian, the defence minister. France has certainly been in the lead in pushing for intervention in Mali. It drafted a United Nations Security Council resolution authorising a regional African force to retake rebel-held territory, which was unanimously passed last October. In a speech to a gathering of French-speaking countries in Senegal last year, Mr Hollande spoke of a “reign of terror” in Islamist-held Mali, where sharia law has been applied in the furthest north.

France is particularly worried that the Sahel is becoming an “Afrighanistan”—a breeding ground for terrorists—thanks in part to modern weaponry that has spilled over the Libyan border after the war there. France itself has been named as a target by groups based in the north; this weekend, as the airstrikes began, the country raised its terrorism-security alert. France also has strong commercial links in the region, and there are currently eight French hostages in the region.

Mr Hollande had also made clear that it was no longer his intention for France to play the role of regional gendarme, stepping in to prop up African rulers, as has been the post-colonial tradition under the Fifth Republic. “Françafrique”, the opaque mesh of military, political and commercial ties, was over, he claimed. Until now, he had insisted that France would offer no more than logistical support to a regional African force, which was laboriously being put together for this autumn.

Which is where the element of familiarity comes in. The reality, acknowledged privately by French sources, is that the Malian army was in no position to defend itself, and that the regional African force was going to take too long to assemble. Mr Hollande stressed that France was acting with a legal international mandate, and responding to a request from the Malian president, Dioncounda Traoré, for help. In a diplomatic breakthrough of sorts, Algeria granted France permission for fighter jets to fly over its airpace. Laurent Fabius, the French foreign minister, said on French radio on January 13th that France had little choice but to intervene urgently or Islamist forces might have made it to Bamako, with “appalling consequences”.

However much successive French presidents say that they want to put an end to post-colonial intervention in Africa, with few other takers for the job it usually proves irresistible at some point. Nicolas Sarkozy, Mr Hollande’s predecessor, had also promised a new era, only to end up sending the French army to help Côte d’Ivoire forcibly evict Laurent Gbagbo, the loser of that country’s presidential election, from office.

The question now is how long the French are prepared to intervene, and how fast a decent African ground force can realistically be put in place. Mr Fabius has talked of “a question of weeks” for the French intervention. He insists that its main contribution is air power, with the few hundred special forces on the ground essentially picking out and verifying targets.

It is the West African force that is supposed to carry out the operation to retake the north from Islamists, and there is a regional meeting on this now set for January 19th. Initial contingents of troops from Senegal, Niger, Burkina Faso, Nigeria and Togo are now due to arrive within days. But a properly manned force will still take time to assemble. France, in short, is likely to find itself involved for a while. Mr Hollande himself has stated that the French operation would last “as long as necessary”.