The M23, a Rwanda-backed armed group, has seized most of Goma, a key city of a million people in the mineral-rich eastern DR Congo.
Analysts say their motives combine security and economic interests with the deadly momentum of war.
Why did Rwanda and M23 take Goma? Rwanda's President Paul Kagame says its priority in the eastern Democratic Republic of Congo is to destroy the Democratic Liberation Front of Rwanda (FDLR in French), formed from remnants of the forces that committed the 1994 genocide.
Many say Rwanda is more interested in the region's rich resources of tantalum and tin used in batteries and electronics worldwide as well as gold. "There is a desire to control the resources of eastern Congo," said Thierry Vircoulon, of the French Institute of International Relations, dismissing talk of the FDLR as a "pretext".
