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?

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.

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"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 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........

© Deutsche Welle