SUDAN

The largest country in Africa, it has suffered a long series of insurrections which have divided the ruling party in the capital, Khartoum, from much of the country.

KHARTOUM

By 2003, Sudan's capital was experiencing a new prosperity from the discovery of offshore oil, and Sudan's government had a new supporter -- China -- who was buying that oil.

DARFUR

A region in western Sudan, it is the size of France and home to 6 million Muslims. By 2003, the Sudanese government in Khartoum was prospering from new oil wealth, and rebel groups in Darfur emerged to claim a share of it.

SOUTHERN SUDAN

It had endured a vicious 21-year civil war between the largely Muslim north and the Christian Sudanese in the south. A North-South peace agreement was in the works when the Darfur killings began -- one reason why the West delayed taking action.

CHAD

Tens of thousands of refugees fleeing the killings in Darfur have crossed into neighboring Chad in search of safety. But militia attacks have spread into Chad, and the border area has become a danger zone for unprotected refugees and humanitarian aid workers struggling to deliver relief.