UNITED NATIONS - How could a rebel band that started with just a few hundred men take over a huge chunk of Africa's biggest country, set presidents against each other and leave the United Nations reeling?
Easy when it is the Democratic Republic of Congo, according to analysts and diplomats, who say a corrupt and disappearing army, alleged meddling from neighboring Rwanda and a UN force with its wrists tied create a chaotic mix.
The M23 rebels have in just one week moved out of a small corner of DR Congo's North Kivu to take over most of the province -- an area twice the size of Belgium and rich in diamonds, precious metals and minerals.
The rebels, armed by Rwanda, according to UN experts, broke from the main government DR Congo army in April with barely 500 men.
The said they were protesting that a 2009 peace accord, intended to end conflict in the Kivu region over the past decade, had not been applied.
But now they simply say they want to unseat President Joseph Kabila, while the United Nations warns that they are killing opponents and raping women as they spread their control.
More than 100,000 people have fled their homes, according to the UN Children's Fund (UNICEF). Children's centers in Goma, the North Kivu capital, are overflowing with thousands of displaced and cholera has been reported.
The DR Congo army collapsed in the face of the rebel force, which had grown to an estimated 3,000 by the time it moved on Goma. The army "simply melted away," according to UN peacekeeping chief Herve Ladsous.
The UN mission in DR Congo, MONUSCO, is the UN's biggest peacekeeping force with more than 17,000 troops, costing $1.5 billion a year.
But its UN Security Council mandate is to protect civilians, not to fight rebels on its own, Ladsous insisted.
UN Secretary General Ban Ki-moon is to report soon on how to reinforce the UN troops, who come from 50 countries but mainly India, Pakistan, South Africa and Morocco.
Meanwhile, the role of Rwanda has sparked controversy.
This week's report by UN experts said the M23's "de facto chain of command" includes Bosco Ntaganda, a Rwandan wanted by the International Criminal Court for war crimes, and "culminates" with Rwandan Defense Minister James Kabarebe.
The report said arms and troops had come across the border.
The Rwandan government has expressed outrage and denied the allegations and Uganda has threatened to pull its troops out of peacekeeping missions over the report's claims about its own backing for M23.
"The evidence against Rwanda is compelling, against Uganda less so," said one UN diplomat.
UN officials say there is no "direct evidence" that Rwanda bolstered the rebels for this advance.
But their suspicions were raised by the number of English-speaking officers they have encountered at checkpoints on roads leading to strongholds of the French-speaking bandits.
There has also been a change in M23 tactics and weaponry.
"On Thursday when they launched their first attack, they were not able to repulse the Congolese army," said one UN official. "On Friday there was a bit of a lull and on Saturday morning it was just like a Blitzkrieg."
Peter Chalk, a senior political scientist at the RAND security research organization, said the DR Congo army is a "complete shambles" while the Rwandan military "is one of the most efficient in Central Africa."
"If the M23 are indeed receiving weapons and training and even support from Rwandan frontline troops that would account for the ease for which they went through that area," he said.
"Basically they had a free run to do what they wanted, a combination of the ineptness of the DR Congo military, the attitude of the UN and the added benefit of support from Rwanda," he said.
Apart from the the UN experts, an independent group, no UN official has publicly accused Rwanda. And Ban and other UN leaders are now encouraging Kabila and Rwanda's President Paul Kagame to start political talks.
Diplomats say it will be a tough task because of the lack of trust between the two leaders.
"There is a need to prioritize political solutions," said Ladsous, who added that more energy had to be put into strengthening border monitoring.
Chalk at Rand said the future of DR Congo may now be at risk.
"The DRC is the biggest country in Africa and it may just be that it is too big and complex a state to exist as a single unified country," he said.
"The history of the country, the various interests of neighboring states makes it basically a very untenable place to govern."
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