Darfur is a semi-arid western province of Sudan - Africa's largest country. Darfur alone is the size of France.
In an Arab-dominated country, Darfur's population is mostly black African.
For years, there have been tensions between the mostly African farmers and the mostly Arab herders, who have competed for land.
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Opposition groups in Darfur say the government neglects their province, and discriminates against black Africans.
The conflict began in 2003, when rebel groups began attacking government targets.
In retaliation, the government launched a military and police campaign in Darfur.
More than 2m people fled their homes.
Many spoke of government aircraft bombing villages, after which the Arab Janjaweed militia would ride in on camels and horses to slaughter, rape and steal.
The refugees and some western observers said there was a deliberate attempt to drive black Africans out of Darfur.
The government admits mobilising "self-defence militias", but denies links to the Janjaweed and says the problems have been exaggerated.
Those who fled the violence are now living in camps across Darfur. About 200,000 refugees have crossed the border into Chad.
Those living in camps now depend on food aid from international donors.
Aid agencies have repeatedly warned that continuing violence is making it difficult, or impossible, for them to provide the displaced people with the help they need.
Attempts by the African Union (AU) - a grouping of African states - to end the conflict resulted in a peace deal being signed in 2006.
The Sudanese government backed the deal, but only one rebel faction - Minni Minawi's faction of the Sudan Liberation Army - signed up.
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As part of the deal, the government agreed to disarm the Janjaweed, but there is little to suggest that this has happened.
At the same time, Minni Minawi's men now seem to be fighting on the side of the government against the other rebel groups.
All this means that violence has actually increased since the peace deal was signed.
The AU has sent 7,000 soldiers to try to monitor a ceasefire.
The Sudanese government agreed to allow this force to operate.
But this relatively small force has not managed to end the violence.
Britain and the US have been pushing for the United Nations to take over the peacekeeping mission and the AU is happy to stand aside.
Sudan, however, says it will not allow a UN force on its territory.