The United Nations, which had a significant number of peacekeeping troops in the city, soon authorized a new intervention brigade of 3,000 troops, with an aggressive new mandate. Likewise, Congo recalled dozens of officers to the capital, Kinshasa, streamlining an army often best known for corruption and human rights abuses.

The question is whether the Congolese military, supported by United Nations peacekeepers, can and will take on the dozens of other armed groups in the area, restoring order throughout the region.

The broad diplomatic pressure on Rwanda appears to have robbed the rebels of backing at a crucial moment. Last year, United Nations experts accused Rwanda and Uganda of being so central to the group’s operations that its de facto chain of command “culminates with the minister of defense of Rwanda.” The report came under intense criticism from Rwanda, but many nations, as well as the European Union, Rwanda’s largest donor, froze aid in response.

“The international pressure on Rwanda seems to have made a difference,” said Ida Sawyer, senior researcher with Human Rights Watch. “They will hopefully think twice before backing yet another abusive rebellion.”

M23 was weakened even before the most recent battles. The group — which formed when more than 1,000 former rebels who had been integrated into the Congolese Army mutinied, breaking away and naming themselves M23 after the date of a failed peace deal between the two sides, March 23, 2009 — was plagued by infighting and a rising tide of defections. In March, Bosco Ntaganda, a rebel general accused of massacring civilians and building an army of child soldiers, turned himself in to the American Embassy in Rwanda, asking to be sent to the International Criminal Court in The Hague.

Mr. Ntaganda, whose nom de guerre is the Terminator, commanded troops accused of killing more than 100 civilians in the Congolese town of Kiwanja five years ago, while United Nations troops hunkered down, unaware, in their nearby base.