The M23 group was named for the peace deal of March 23, 2009, which they accuse the government of violating. The soldiers, mostly Tutsis, became part of the national army through that accord. However, they broke away from the Congolese army in April, complaining they weren't being promoted as promised, and because of a lack of pay and poor conditions.

Tens of thousands of Congolese, already displaced by previous rounds of fighting in the volatile region, have fled camps around the edges of Goma, according to UNICEF and the medical charity Doctors Without Borders.