Rebels from the Tuareg ethnic group now control most of northern Mali, a territory as big as France on the edge of the Sahara desert.
A column of trucks loaded with Tuareg fighters rolled into the ancient desert town of Timbuktu on Sunday, taking over the positions abandoned by fleeing government soldiers.
They include an Islamist faction that wants to impose Shariah law throughout Mali and are believed to include elements with links to al-Qaida in the Islamic Maghreb.
The Tuaregs are nomads, familiar in geography books as the desert warriors who cover their heads and faces with traditional indigo turbans and veils.
The disintegration of Mali could further destabilize a fragile region that is already simmering with political unrest, crime and religious fundamentalism.
It also raises the prospect that the Tuareg rebellion in Mali could spark similar uprisings in other countries that have big concentrations of Tuaregs, including Niger, Algeria and Libya.
Fallout From The Libyan Civil War
The rebels are formidable fighters, says Jeremy Keenan, an expert on the Tuareg people who teaches at London's School of Oriental and African Studies.
"The Tuaregs probably would have given any army a hammering," Keenan says, especially since they were hardened by years of fighting in the pay of Libyan leader Moammar Gadhafi and armed with weapons looted from the ousted dictator's arsenals.
But Keenan says capture of oasis towns such as Timbuktu and Gao was no great feat.
"The fall of these towns doesn't mean a great deal because there was nothing much to fall. The Malian army is pretty useless at the best of times, and they had already beaten a strategic retreat," he says.
The Tuaregs took a heavy toll on Malian soldiers, prompting a mutiny among junior Malian officers who ousted the elected president, Amadou Toumani Toure, just two weeks ago.
The mutineers said they were angry that the president hadn't provided them with the resources or the leadership to face the Tuareg fighters.
But the mutiny further undermined the government's defenses in the north, and town after town promptly fell to the Tuaregs.
Tuareg Factions Vie For Control
The leaders of the main Tuareg rebel group, the Azawad National Liberation Movement, or MNLA, say they have achieved their objective: control of the region they claim as a homeland.
"The military phase for them is completed, but they're not the only ones on the ground," says Yvan Guichaoua, an expert on the region who teaches at the University of East Anglia in Britain.
There is a smaller group, Ansar Dine, led by Iyad Ag Ghaly, a fighter who made his reputation in a rebellion in the 1990s.
Guichaoua says Ag Ghaly is believed to have links to a branch of al-Qaida in the Islamic Maghreb, but that the form of Islam he promotes is not jihadist. Ag Ghaly has said that he wants to impose Islamic Shariah law, not just in the north, but throughout Mali.
It's unclear how strong Ag Ghaly's forces are, but he is said to control Timbuktu, a historic trading center that now has a population of around 55,000.
Some reports have it that Ag Ghaly was joined by local leaders of al-Qaida and was holding talks with local Muslim religious leaders.
His men were reportedly forcing women to cover their faces and ordering shopkeepers to take down advertising pictures that showed unveiled women.
A Moderate Backlash?
Keenan says Ag Ghaly's Islamist fundamentalism is unlikely to go down well in a region that's dominated by the more tolerant Sufi school of Islam.
"I'd be surprised if he survives another two months," Keenan says, predicting that the stronger MNLA will get rid of Ag Ghaly in an effort to broaden its support among moderates.
Ever since the end of the colonial era, Tuareg leaders have claimed that they were oppressed and marginalized by the various national governments.
Tuaregs in neighboring Niger have also rebelled at various times, most recently in a two-year uprising that ended in 2009.
But Guichaoua says that doesn't necessarily mean that Mali's insurrection will cross borders.
"[Tuareg] people move between these countries, and sometimes they have family ties as well," he says. "These groups keep exchanging information with each other, but that doesn't necessarily mean that groups outside Mali are immediately ready to take up arms."
Guichaoua says he believes that Niger is the country that would be most vulnerable to an uprising, but that authorities in Niger are putting a lot of effort into defusing a confrontation.
Guichaoua says a wider Tuareg rebellion could also be provoked if outside troops attempt to intervene in Mali.
"ECOWAS [Economic Community of West African States] is considering sending troops to Mali, and I think that could be disastrous for the region," he says, adding that Tuaregs in the neighboring countries might come to the defense of the Tuareg rebels in Mali.
A Tough Call For U.S. Policymakers
Keenan says the stakes are high, not only for the countries in the region, but also for the United States and European countries.
The U.S. State Department calls Mali "a leading regional partner in U.S. efforts against terrorism," and the U.S. has donated equipment to the Malian army under a program called the Trans-Sahara Counterterrorism Partnership.
But Keenan charges that the terrorism threat was hyped by U.S. officials who wanted an excuse to build a presence in Africa.
He calls U.S. policy in the region "staggeringly uninformed," and says any U.S. intervention in Mali now would provoke a backlash.
Keenan also believes that Algeria plays a spoiler role in the region, stirring up instability in an effort to justify its own heavy-handed tactics against dissidents.
Algeria's military-backed ruling party is in partnership with the U.S. and European powers to contain what the government says is a growing threat from groups aligned with al-Qaida.
Keenan says Tuaregs in Algeria are angry at the state for closing down tourism in their region under the banner of fighting terror. "Algeria is worried because unrest in the south could well trigger the big bang further north."
For its part, the U.S. State Department has issued a travel warning for Mali, noting that "rival rebel factions are battling each other for control in areas they have seized in the north."
The warning also cited "continuing threats of attacks and kidnappings of Westerners in the north of the country."
The Obama administration has banned the Malian army officers who led the coup from traveling in the United States and demanded that they return the country to civilian rule.