French troops entering Mali to quell an Islamist insurgency face a tough battle against a well-coordinated coalition of militant groups.
The militants have entrenched themselves in the West African nation in the past year, exploiting the weakness of their opponents.
Since last week, several Islamist factions have been trying to expand their control of northern Mali into the government-held south, home to the capital, Bamako. On Monday, they captured a town, Diabaly, only 400 kilometers away.
France began sending hundreds of ground troops to Mali last week to try to reverse the Islamist advance. West African forces also are expected to arrive in the weeks ahead to support the French effort.
Mali has welcomed the intervention of former colonial ruler France and neighboring African states. Analysts say Bamako has been forced to accept the help because its troops are poorly-trained and its interim government is plagued by infighting and interference from army officers.
J. Peter Pham, an Africa analyst at the Atlantic Council in Washington, said the Islamist groups cooperate closely and their memberships tend to overlap.
Mali's Islamist coalition
One of the Islamist groups leading the insurgency is Ansar Dine, a home-grown movement that seeks to convert Mali into an Islamic theocracy.
Ansar Dine teamed up with ethnic Tuareg rebels to oust government forces from northern Mali last April. It later turned its weapons against the lesser-armed Tuareg fighters and seized control of the region in June.
Since taking over the north, Ansar Dine has joined forces with two regional militant groups - al-Qaida in the Islamic Maghreb (AQIM) and the Movement for Unity and Jihad in West Africa (MUJAO), an offshoot of al-Qaida's North African branch.
African diplomats also have said Nigeria-based Islamist group Boko Haram is active in northern Mali. But it is not clear whether Boko Haram is involved in the fighting there.
In an article published in November, former U.S. assistant secretary of state for African affairs Herman Cohen wrote that the goal of the Islamists is to "spread their control to the rest of Mali and then on to neighboring Mauritania and Niger."
Northern Mali's Islamists have used several strategies to develop into a fighting force whose effectiveness has surprised French officials.
Analyst Bill Roggio of the Washington-based Foundation for the Defense of Democracies said the militants primarily secured their weapons from neighboring Libya, where arms depots were looted during the 2011 revolution that deposed dictator Moammar Gadhafi.
"These are desert borders with a lot of smuggling routes, so the militants are able to move weapons back and forth pretty much with ease," Roggio said.
He said the Islamist arsenal includes pick-up trucks mounted with machine guns and rocket launchers and armored vehicles seized from the Malian army.
Pham said the militants also have earned millions of dollars from kidnapping foreigners for ransom and involvement in drug-trafficking.
"They adopted a strategy of marrying into the local communities and working with them to facilitate their illicit rackets," he said. "And they have plowed the funds into the acquisition of weapons and fighters, building up capabilities far in excess of the Malian military."
Analysts say the Islamists have recruited several thousand fighters who have a deep knowledge of the desert terrain and experience in defending it.
Islamist fighters easily defeated the Tuareg rebel group MNLA last year after it objected to their imposition of Islamic law, or sharia, in northern Mali. Since then, the Tuareg rebels have mostly stayed on the sidelines of the conflict as they consider their next move.
The Tuaregs launched a rebellion last January to seek independence from a southern-based government that they have long accused of marginalizing them.
Pham said the predominantly secular nomads may be provoked into a counter-insurgency against the Islamist forces they see as their new oppressor.
"The main weakness of the Islamists is that they imposed a harsh version of sharia upon an unwilling population. They also destroyed centuries-old monuments in Timbuktu and other places that are dear to the hearts of the local population."
Roggio predicted the Islamist groups eventually will be outgunned by an expanding contingent of French and West African troops.
"I do not believe that ultimately the Islamists will be able to stand up against a concerted effort by a professional military like the French," he said.
"They may draw back and wait until the French forces withdraw before trying to attack African forces that would be easier targets."
A previous version of this story contained a quote about MUJAO military chief Omar Ould Hamaha. VOA determined the the quote was incorrect and has removed it from the story.