DIABALY, Mali -- On Jan. 14, Diakaridia Doumbia locked his door, climbed to the second floor and peered down from his mud-brick home at a swarm of cocaine-drugged Islamist rebels who’d captured the town of Diabaly earlier that day.

The towering retired soldier, now graying, placed a call to a friend in the Malian military.

"They are outside my house. They look like they are packing their cars to keep driving," he reported. Soon after, French jets swooped down and struck, obliterating several of the cars and incinerating their inhabitants.

Later, Doumbia received a call. This time, the man on the other line wasn’t Malian.

"It was the French commander. He called often, and we talked. I told him where the rebels were and what they were doing," said Doumbia, who served in the Malian military from 1974 until 2007.

The French beat back the sudden Islamist advance south into Diabaly with heavy air power, but it turns out they had some help: Doumbia and a spontaneous network of residents who responded to the capture of their farming community by risking their lives to channel intelligence out of the town.

"Everyone was calling," said the mayor, Oumar Diakite, who was out of town when Diabaly was attacked and then was summoned by the governor. Diakite compiled the reports in real time – working next to detailed computer grids of the area that had been saved from U.S. development projects in the area’s complex canal system – and reported the coordinates to the military, which relayed them to the French command.

The townspeople’s response will pose a serious problem for the rebels if it’s replicated elsewhere. Fighting an insurgency against a more powerful force is hard, but it’s even harder without local complicity.

Part of the town’s disgust stemmed from the intruders’ behavior, and one trait in particular: Many of the outsiders, some of whom belonged to the regional al Qaida group and quickly banned cigarettes in the town, apparently were druggies.

Doumbia and one other Diabaly resident reported watching the rebels regularly taking cocaine. A third resident reported seeing emptied, white-coated bags lying around and said everyone knew what was inside them.

"We saw them sniffing it, smoking it. Some were injecting it," Doumbia said.

A bag of white powder was flung outside the gate of a friend’s house after one bombing raid, the contents equal to half a kilogram of sugar. Doumbia sent a child to fetch it and confirm its contents, he said, but it was already gone.

Experts say the Sahara desert in West Africa, with its loose borders and weak governments, is rapidly becoming one of the prime cocaine-trafficking routes in the world. Its lucrative windfall is thought to help finance the Islamist rebels, and a legion of fighters dependent on the drug might make finally squelching the insurgency even more difficult.

A U.S. official said the cocaine trade was definitely a driver of the conflict but that the inflow of foreign fighters and imposition of Shariah law suggested that ideology was the primary motivation for the insurgency.

"My view is that the drug thing is a factor, but it’s not the root cause of their actions," said the official, who was cleared to speak only on the condition of anonymity.

The communication lines the townspeople of Diabaly opened after their occupation worked both ways. On the first night the rebels were in town, the mayor – prompted by the French – spread the word that airstrikes were coming and told the population to gather in a far area of town.