HERE we go again.

The news that the UK Government has agreed to support the French intervention in Mali was greeted yesterday with weariness and wariness. Nobody was fooled by the ease with which the French swept into Timbuktu, a place whose very name has come to mean outlandish and inaccessible. One lesson of Iraq is that winning a war is the easy bit. It is winning the peace that counts. And one lesson of Afghanistan is that, once your enemy disappears into remote mountains strung across a long and porous border, it can take years to dislodge him.

In Mali the story has an added edge. Years of poverty and drought have proved effective recruiting sergeants for jihadist extremism all over the Sahel and now they are well armed, thanks to fresh supplies of guns, ammunition and rockets, looted from Colonel Gaddafi's arsenals in Libya.

Loading article content

Defence Secretary Philip Hammond yesterday gave assurances that there were no plans for British troops to take on combat roles. They would be mainly operating a Sentinel spyplane, staffing a transport plane and training African peacekeepers. To this Labour's Frank Dobson retorted grimly that "the American catastrophe in Vietnam started off with American troops in a training capacity". Meanwhile former head of defence staff, General Sir Mike Jackson, warned of protracted guerrilla warfare.

Nevertheless, Britain has a moral obligation to help, if carefully calibrated short-term intervention can make a decisive difference. It is not in anybody's interests to have a vast, lawless training ground for terrorists in northern Africa. Regional oil and gas interests and the miserable lives of the people of northern Mali, bearing the savage puritanism of strict sharia law, are less important factors than the continuing existence of a large failing state. Short sharp interventions can stabilise such situations, as the UK action on Sierra Leone in 2000 did.

Some of those fighting the Malian government were not jihadists but Tuareg warriors with well-founded but essentially local grievances. The challenge is to distinguish between the two and then eliminate the former and negotiate with the latter. That will require good intelligence as well as some brute force. It is important to remember that most African Muslims want cars, TVs and enough to eat, not a global caliphate.