THE RESIDENTS of Goma are no strangers to war. The largest city in the east of the Democratic Republic of Congo (DRC) has long been a refuge for those fleeing from violence elsewhere in one of the world’s most blood-soaked regions, where more than 100 armed groups compete for land, loot and political influence. On January 26th the most sophisticated of these militias, a group known as M23, brought war to the city itself. Its apparent seizure of Goma, the culmination of more than two years of resurgent violence by the previously dormant group, illustrates the enduring weakness of the Congolese state. It is also a worrying sign that M23’s patron, Rwanda, may be willing to use its strength to redraw the map of the region—and, in doing so, risk another catastrophic African war.