The most important news in the world today isn’t about the civil war in Syria or the talks with Iran, but—if it holds up—the end of the seemingly endless conflict in central Africa, along the Congo-Rwanda border and the surrounding region. That’s where as many as 5 million have died since the mid-1990s (not counting the 800,000 who perished in Rwanda’s genocide in 1994).

Not only are millions dead, but as The Guardian reports, half of the region’s adults suffer from post-traumatic stress disorder and one-fifth have considered suicide.

There’s still a long way to go, and there are plenty of armed groups still active in the area. But the apparent defeat and surrender of the M23 group is a major breakthrough and a step toward finally ending that incredibly destructive, interlocking series of wars. (A good account of the early and middle phases of the war, from 1996 through 2010, can be found in the wonderfully written but chilling book Dancing in the Glory of Monsters, by Jason K. Stearns.)

Russ Feingold, the former senator from Wisconsin who’s the US representative for the wars in central Africa, allowed himself to say: “This is a critical and exciting step in the right direction [in] one of the toughest problems in the world.” He added:

“This is a test case—it has great promise. It has enormous potential to add great credibility to UN peacekeeping operations (in other conflict zones). It has great promise and significance.”

A big reason M23 was able to sustain its senseless rampage is that it had the support of Rwanda, which had for years used proxies to intervene in the eastern Congo. Last year, a special report by a United Nations team of investigators pointed directly at Rwanda’s defense minister as responsible for M23:

The Government of Rwanda continues to violate the arms embargo by providing direct military support to the M23 rebels, facilitating recruitment, encouraging and facilitating desertions from the armed forces of the Democratic Republic of the Congo, and providing arms, ammunition, intelligence and political advice. The de facto chain of command of M23 includes Gen. Bosco Ntaganda and culminates with the Minister of Defense of Rwanda, Gen. James Kabarebe.

And the report added:

Senior officials of the Government of Uganda have also provided support to M23 in the form of direct troop reinforcements in Congolese territory, weapons deliveries, technical assistance, joint planning, political advice and facilitation of external relations.

Part of the reason why M23 decided to lay down its arms is because troops from the Congo more effectively battled there since the fall of a strategic city to M23, but perhaps more important is the fact that the UN and the African Union have engaged in the region and that world powers—including, rather late, pressure from the United States—have placed major pressure on Rwanda to halt it support for the group. As The New York Times reports:

On the diplomatic front, the United States, the European Union, Britain and other nations had already begun cutting aid to Rwanda—which has been accused of helping arm, coordinate and recruit fighters for the insurrection—in a move that appears to have shorn the rebels of badly needed support.

Last week, Jason Stearns reported in his blog what turned out to be the prelude to M23’s apparent stand-down:

The new round of fighting between Congolese government forces and the M23 rebels is reaching a dramatic climax. With the Congolese army having swept through all of the major towns that the M23 held—Kibumba, Rumangabo, Rutshuru, Kiwanja, and since this afternoon Bunagana—the M23 may be nearing its end. This would be historic—it would be the first time the Congolese government had defeated a major rebellion, and it would be the first time since 1996 that an armed group allied to Rwanda is not present in the eastern Congo. It is, however, too soon, to declare an end to the M23, as the rebels reportedly still occupy the hills along the Rwandan border between Runyoni and Tshanzu.

Stearns notes that the UN actions were critical:

[A] second factor was the United Nations. Observers on the front lines reported that the Congolese soldiers were being issued military rations by the UN, and that UN officers were jointly planning operations with the Congolese army. UN attack helicopters have been providing support, although the bulk of the fighting has been carried out by the [Armed Forces of the Democratic Republic of the Congo].

As the Times report notes, the UN presence isn’t small:

The United Nations force consists of nearly 19,000 military personnel. The annual cost has risen to close to $1.5 billion. But it was the arrival of the new, offensive-minded intervention brigade and its tough new Brazilian commander that changed the tenor of the mission.

But Stearns emphasizes the importance of the pressure on Rwanda:

But it may be the third factor that was the determining one—the absence of support from Rwanda. According to several reports from the frontlines, despite indications of some cross-border support in the Kibumba area, the M23 was largely left to its own devices. “The Rwandans just wouldn’t pick up their phone calls,” one source close to the M23 leadership told me. This is a drastic change from August, when many sources—the UN, Human Rights Watch, and foreign diplomats—all reported hefty support coming across the border. The fact that the M23 did not put up much of a fight in Kiwanja and Rumangabo was another indication that they knew they stood no chance against the superior firepower of the UN and the FARDC. According to several diplomats, the US Secretary of State John Kerry as well as a senior British diplomat called President Paul Kagame last Friday to impress how important it was for Rwanda to sit this out. While similar pressure has been applied before—President Obama called his Rwandan counterpart with a similar message last December—this time it may have just been the final straw for the Rwandan leaders.

Last year, Susan Rice—now President Obama’s national security adviser—came under sharp criticism for her long-running support for Rwanda:

Support for Mr. Kagame and the Rwandan government has been a matter of American foreign policy since he led the Tutsi-dominated Rwandan Patriotic Front to victory over the incumbent government in July 1994, effectively ending the Rwandan genocide. But according to rights organizations and diplomats at the United Nations, Ms. Rice has been at the forefront of trying to shield the Rwandan government, and Mr. Kagame in particular, from international censure, even as several United Nations reports have laid the blame for the violence in Congo at Mr. Kagame’s door.

Added the Times, in its account of Rice’s too-close relationship with Kagame:

Aides to Ms. Rice acknowledge that she is close to Mr. Kagame and that Mr. Kagame’s government was her client when she worked at Intellibridge, a strategic analysis firm in Washington. Ms. Rice, who served as the State Department’s top African affairs expert in the Clinton administration, worked at the firm with several other former Clinton administration officials, including David J. Rothkopf, who was an acting under secretary in the Commerce Department; Anthony Lake, Mr. Clinton’s national security adviser; and John M. Deutch, who was director of the Central Intelligence Agency.

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