NIAMEY, Niger -- The French capture of the airport at Kidal, the last of the major Malian towns overrun last year by al Qaida-affiliated militants, very likely marks the beginning of the end of France’s aggressive advance against the insurgents. What comes next may prove much more difficult: hunting down an Islamist foe that for the most part is still at large in vast, trackless desert expanses.

France already may be seeing a glimmer of the challenges that lie ahead. French and Chadian special forces at the airport have yet to enter Kidal, a desert outpost near Mali’s border with Algeria and Niger that’s dominated by the Tuareg, a distinct ethnic group whose rebellion a year ago after flooding in from Libya started northern Mali’s sudden collapse. The Tuareg separatist movement, the National Movement for the Liberation of Azawad, quickly pushed the Malian army out, only to be shoved aside by Islamist militants, including al Qaida in the Islamic Maghreb.

Now, with France quickly pushing the al Qaida-linked militants back, the National Movement for the Liberation of Azawad claims to have retaken a flurry of desert posts in advance of Mali’s military. France has close ties within the Tuareg community, and Francophone Africa’s news media have been full of speculation of backroom deals.

"The reason we have not attacked is because France is negotiating with MNLA, who is inside," said Hassan Sylla Bakary, the minister of communications for the government of Chad, whose country is providing hundreds of troops for the French-led offensive.

Keeping the Tuareg separatist movement on the side of the anti-Islamist campaign is something the French would like to have happen – and something that Ag Mossa Attaher, the movement’s spokesman, said his group would prefer as well. But first, the movement would like to negotiate the status of Azawad, as it calls its desert homeland.

"The French minister of defense has acknowledged that there is a political problem that needs to be resolved in Azawad, and that’s why they have not fought us in Kidal," Attaher said. "Our demands are known. It is our territory."

Chief among those demands is keeping the Malian army from returning to Kidal, a position unlikely to be viewed happily in Bamako, the Malian capital hundreds of miles to the south. Without the Malian army to occupy Kidal, only Chadian troops right now are allied with the French in what appears to be an increasingly complex stew of political and ethnic rivalries.

That means the turbaned Chadians are likely to take over France’s security mission.

Chad, like Mali and Niger, a former French colony, has sent more troops than any other African nation to battle alongside France, even though it isn’t a member of the West African bloc of nations that the United Nations originally tasked to organize an intervention force for Mali.

On Wednesday outside Niamey, the capital of Niger, nearly 50 military vehicles – including four fuel trucks and seven BMP tanks – packed with some 600 men rolled north toward Mali, where Chad already has more than 1,000 troops. Altogether, Chad has promised to commit 2,200 troops to the battle in Mali.

Feisty eyes and bright sunglasses poked out from under an array of turbans: white, brown and a wild spectrum of camouflage.

"Our objective is to completely eliminate all the Islamists," proclaimed the group’s commander, Col. Hemchi Ramdan, who sported gold-rimmed sunglasses.