In days, a tiny rebel army – comprising just a few thousand men – has grabbed an area of land in the Democratic Republic of Congo almost the size of France. After government forces, along with UN peacekeepers, put up almost no resistance to the rebel advance, President Joseph Kabila has been forced into a humiliating climbdown. He's promised to "look into" the grievances of the rebels, after previously vowing not to negotiate with them.

Meanwhile, the leaders of the M23 rebel group have declared their intent to march all the way to the country's capital, Kinshasa – a distance equivalent to the journey from Berlin to Moscow.

How has this happened?

For a start, you need to understand how this conflict has swelled in recent months – and the motives of Rwanda, M23's key backers.

But there's a bigger picture. For decades, eastern Congo has been the site of intense fighting between different militias, keen to get their hands on the region's vast mineral wealth. Caught in the middle, residents have suffered unimaginably: hundreds of thousands have been killed, raped, tortured and displaced, and many children have been forced to fight. The appalling crimes committed on all sides (including by the Congolese army and even some so-called UN peacekeepers) have been well documented. But the international community's failure is perhaps the most shaming aspect of all of this.

Writing in the Guardian, Michael Deibert lays out the background to this latest crisis, arguing that the 2009 Congo peace deal, backed by the UN and western governments, was "a false accord, leaving the people of DRC at the mercy of their tormentors":

Far from a road to Damascus moment, the agreement was rather a modus vivendi by cunning, ruthless political operators.

[DRC President] Kabila, re-elected in a highly controversial 2011 ballot, has fashioned a government that is in many ways a younger, more sophisticated version of his father's [the former DRC president Laurent Kabila]. Relying on a narrow circle of trusted individuals and a network of international alliances, Kabila's power is built on patronage rather than a political base...

Across the border, Rwandan President Paul Kagame, for so long a darling of western donors and development workers, has for many years presided over a tight-lidded dictatorship where government critics meet either death...exile.. or both.

As a number of people (myself included) warned at the time, the peace deal as implemented was a marriage of convenience destined for a nasty divorce. Unfortunately, the international community itself gave an additional seal of approval when, against the advice of their own Office of Legal Affairs, UN forces backed Congo's army as the latter launched Operation Kimia II ("Quiet" in Swahili) in March 2009 against the FDLR [another rebel group, many of whom are part of today's conflict].

According to one investigation, between January and September 2009 more than 1,400 civilians were slain in the provinces of North and South Kivu, at least 701 by the FDLR and the rest by Congolese and Rwandan government-allied forces. Over the same period in the same provinces, over 7,500 women and girls were raped and over 900,000 people forced to flee their homes...

The approach of the international community thus far, both in exercising its mandate to protect civilian lives in Congo and in holding the outside supporters of Congo's rebel groups to task, has thus far proved woefully insufficient.

Many people must have asked themselves, as they watched the tiny rebel army this week sweep into Goma, regional capital of eastern Congo and home to up to 1 million people: why aren't the government and the UN troops stationed there doing more to stop this? The answer is partly that the UN mandate did not permit it. It is partly that if they had resisted it would have caused much more bloodshed, much more loss of civilian life in a heavily populated area which has already suffered so much.

It is also partly that the so-called authorities have failed this region so badly, the government and rule of law has been so absent for so long, that there was probably little they could have done, even if they had wanted to.

Diebert continues:

As word of Goma's fall spread throughout Congo, reaction was immediate. Buildings belonging to Kabila's political party – with many Congolese accusing the president of caving in to the Rwandans – were burned in the cities of Kisangani and Bunia, and UN buildings were pelted by stones in the latter town.

The fall of Goma may prove a defining moment, for both the Congolese government and for the gulf between the actions and the words of the international community in the Democratic Republic of Congo.