The Nuer and Dinka have a long history of trouble between them. It's not certain exactly when this long-standing feud began, but there's no doubt why there's such animosity between the two tribes: no one knows for sure where Nuer land ends and Dinka land begins. As it's impossible to know precisely which strip of land belongs to which tribe, territorial disputes are an all too regular occurrence.

The prevalence of drought in this part of Sudan gives the feud an even more dangerous edge, as both Nuer and Dinka need to have access to a regular supply of water. The natural tendency of the tribes is to lay claim to those areas richest in water. Over many years, this had led to numerous conflicts—some large, some small—which have caused the deaths of many people on both sides.

Sudan is already ridden with conflict as it is, with a long and bloody war raging between the government and South Sudanese rebels. But this war, the war over territory and water supplies between the Nuer and the Dinka, has been going on for hundreds of years. And without anyone making the effort to draw up precise boundaries between the tribes' respective territories, this war looks set to continue for hundreds more.