NIONO, Mali -- The new frontline in the war on terror runs alongside a 20-meter-wide canal where a dozen or so Malian government soldiers and a handful of French armored personnel carriers now stand guard against an Islamist force that clearly is not backing down.

A signpost points the way north down a gravel road to Diabaly, some 40 miles away, where on Monday a rebel Islamist unit surprised a Malian garrison and overwhelmed it.

Two days later, fleeing refugees reaching here by car, donkey cart and bicycle reported seeing no signs of a much discussed counteroffensive to reclaim Diabaly. The 40 miles between Diabaly and this administrative hub was a no-man’s land, they said.

“I did not see a single Malian soldier,” said Cheikh Omar Dicko, who fled the whole way on a motorbike, with a friend on the back. “Not one.”

France’s short celebratory honeymoon in halting Islamist gains in Mali was dashed at Diabaly, when an Islamist force routed roughly 200 Malian troops from a small garrison in the village. The Malians were ambushed from behind, and many fled through a grove of mango trees and knee-high water.

It was a battle that taught the French some lessons about the anti-jihadist campaign they’ve begun:

– Air power is of limited benefit without ground troops capable of fending off the rebels – and the Malian military cannot.

– Their enemy is cunning, well-armed, brave, and already adapting to neutralize France’s air power.

– The terrain, especially on this front, will not be their friend.

The story of the battle for Diabaly is still unfolding. But interviews with officials here and fleeing residents tells of a cunning Islamist force using all its advantages to take new ground, even in the face of a modern Western nation deploying air power.

The story begins in the town of Goma, which sits about 13 miles north of Diabaly. The rebels captured it months ago, marking the southern edge of an Islamist-controlled expanse that stretches from the western banks of the Niger River, north to the historic city of Timbuktu, and northwest to the porous border with Mauritania.

When the French began arriving in Mali on Friday, the Islamists sent reinforcements to Goma. Then, rather than wait for Malian troops to move into Islamist-controlled territory, the Islamists decided to move south.

The most likely attack route, Malian forces thought, would be a road that runs along a canal between Goma and Diabaly. They prepared to meet the Islamists there.

Instead, the rebel convoy, under the cloak of early morning darkness, turned east off the road three miles outside of Goma, at the village of Dogofru. From there, they navigated through the shrubby terrain toward the southeast.

Some parked their trucks and approached Diabaly on foot from the east, while about 20 other trucks looped around the bank of another canal – dubbed the Millennium Challenge canal by locals, because American aid dollars paid for it two years ago – and attacked Diabaly from the south, through the villages of Alatola and Kourouma.

The Malian soldiers tried to block them at Alatola but were pushed back to their base in Diabaly. There, they were ambushed on their flank by the rebels, who had crossed a swamp by foot to attack the town.

The battle lasted several hours, but before noon the surviving Malian soldiers fled.