Recent escalation: Mostly Christian and animist South Sudan seceded from mostly Muslim Sudan in 2011, about six years after a peace deal ended more than two decades of war. But the sides never fully agreed where their shared border is, nor did they reach agreement on how to share oil wealth in the border region. In recent months, the sides have drawn closer to a full-scale war.
2003: Sudanese forces attempt genocide against the Fur, Masalit and Zaghawa tribal groups in Darfur. An estimated 300,000 are killed, and 2.5 million become refugees.
1990s: Sudan's government sought to bomb and starve the Nuba, killing as many as 500,000.
1980s: Tension between the central government and the south erupts into civil war.
