M23 first surfaced in eastern Democratic Republic of Congo (DRC) in 2012. Thirteen years later, the rebel group is stronger than ever.

In late 2012, controlling large parts of North Kivu province and its capital city of Goma was its biggest — though short-lived — success. However, this time, Bukavu, the capital of South Kivu province, also fell, with fighters advancing alongside 4,000 Rwandan troops.

How has this been possible? And what factors were different in 2013, when Congo's army finally drove the last M23 fighters out of the country, aided by troops from the UN peacekeeping mission in the DRC (MONUSCO) and the newly-formed Force Intervention Brigade?

Defeat doesn't spell peace

Lasting peace is rarely achieved by disarming fighters. When M23 took up arms in 2012, it was on the pretext of the government not fulfilling its obligations laid out in a 2009 peace deal. The so-called National Congress for the Defense of the People (CNDP) had pledged to protect Congo's Tutsi population, but surrendered under the March 23 agreement, after which M23 is named.

"There were various attempts by the Kinshasa government to incorporate CNDP fighters into the Congolese army," said Stephanie Wolters, an expert for Africa's Great Lakes Region at the South African Institute of International Affairs (SAIIA).

"That never really worked because that integration of the CNDP wasn't complete, they became part of the Congolese army but they continued to have their own command and control, their own leadership, and they continued to pursue their own interests."

The absence of state

The state's role is crucial. Time and again, people in eastern Congo have accused the government in the capital, Kinshasa, 1,500 kilometers (932 miles) away, of making too little effort to resolve the conflict.

The security forces are poorly equipped, with no means to enforce state control over Congo's almost 2.5 million square kilometers. What is more, it is not unusual for FARDC soldiers to wait months for their pay — a further incentive to blackmail the population they are deemed to protect.

And the problem doesn't end there. An ineffective army and weak institutions create a power vacuum.

As Pacifique Zikomangane, an expert on international relations, wrote in The International Scholar: "With the absence of the Congolese army and police in these areas, armed groups have become the sole providers of security and administrative services."

From deep roots to modern power politics

Rwandan history in the Congo goes a long way back. Some of the ethnic Rwandans in eastern DRC have in fact been around for more than a century, peacefully coexisting with other ethnic groups. But stability in the region fell apart in the wake of the 1994 Rwandan genocide.

Again, the events in Rwanda had their roots — and certainly, Belgian colonial divide-and-rule strategies left their mark, as Zikomangane noted.

"In an effort to subjugate the majority Hutu population, Belgian rulers adopted more divisive public policies that concentrated power in the hands of the Tutsi elite," he wrote.

The genocide ended when the Tutsi rebel group the Rwandan Patriotic Front (RPF), led by Paul Kagame — who later became President of Rwanda — marched on Kigali. Among the hundreds of thousands who sought shelter in eastern Congo — mainly Tutsi refugees — were Hutu militias fleeing Kagame's fighters.

The region has been restive since then. And the presence of Hutu militants, today organized under the acronym FDLR (Democratic Forces for the Liberation of Rwanda), more than once served Kagame with a pretext to either support militias across the border or send his troops.

Great Lakes expert Stephanie Wolters argues that with no attacks on Rwandan soil in nearly 20 years, Hutu fighters no longer pose a serious threat to Rwanda.

"So this is about something else," she told DW.

"It's about Rwanda's desire to want to control Eastern DRC for its own purposes, and that's really what's happening here. And that's one of the things we have seen over the last few weeks, the expansion of the control of the territory that M23 now holds with the capturing of Goma and Bukavu."

Battling for Congo's mineral wealth

Eastern Congo is home to significant quantities of gold and much of the world's coltan reserves. The mineral group is crucial for laptops and smartphones. According to Richard Moncrieff from the International Crisis Group, raw materials have played a decisive role in the conflicts since the 1990s.

"Both Congolese armed groups and foreign armies including Rwanda's, Burundi's and Uganda's have all intervened in DRC partly as a kind of geopolitical rivalry. They're all trying to push each other back and maintain control over what they see as their areas of influence," said Moncrieff.

"[Lots of] minerals have been shipped out into those three countries, gold, coltan and others, and that fuels the war economy and it's certainly a factor that motivates neighboring countries to intervene in DRC either directly or through proxy armed groups."

Among the triggers for M23's resurgence, observers cite Congo's security partnerships with Uganda and Burundi, while talks with Rwanda failed.

The restraint of the international community

After years of absence, M23 resumed attacks in eastern Congo around four years ago.

Why has it not been possible to push back the rebel group during this time, as was possible in 2013?

In a DW interview at the end of January, Martin Kobler, the former head of the UN mission in Congo, criticized the UN peacekeeping forces for failing to take decisive action, even though they still had a robust mandate.

Next to joint military operations, it was massive international pressure that led to the M23's defeat in 2013. Bowing to that pressure, Kagame also withdrew his support for the militia. Today, the situation is different. Only a few actors took a clear stand in condemning Rwanda's intervention, said Stephanie Wolters.

"The Americans have always been quite clear, the Belgians have been quite clear. France has flipflopped. The UK for a long time was on Rwanda's side because of their own asylum deal. The EU has been all over the place because it's difficult to get consensus," Wolters said.

"So it took an incredibly long time and there's been a lot of reluctance to go down the road of sanctions or condemnation or any kind of punitive action on Rwanda."

Perhaps even more alarming is the fact that African actors have remained almost invisible, as Wolters puts it. Peace efforts in Luanda and Nairobi ultimately failed. Rwanda's President Kagame has thus far refused to withdraw his support for the M23. Congo's President Felix Tshisekedi, on the other hand, firmly opposes direct negotiations with the M23, whom he considers no more than Kagame's proxy army. When the UN Security Council recently met to discuss the situation in eastern Congo, it was its three African members who opposed a clear condemnation of Rwanda.

There are reasons for this reluctance. "Rwanda is strategically extremely smart. And they have known how to make themselves useful," Wolters pointed out.

"Kagame also led AU reform. He's got a really good diplomatic corps. He's got senior people in important positions like head of the francophonie or SRSGs [Special Representatives of the Secretary General, or heads of mission] in different UN peacekeeping missions. And all of this has been cultivated deliberately. And it puts him in a different league than the DRC, if I can put it that way."

Part of Rwanda's strategy consists of contributing peacekeeping troops to Mozambique and the Central African Republic, making it even more indispensable for the international community.

However, experts agree that a harder stance towards Rwanda is the only way forward: Rwanda, which is still dependent on development aid, will only reconsider its role in the Congo under international pressure.

Terry Martin contributed reporting

This article has been adapted from German