Specifically, the Juhayna Arabs, a group that includes both Salamat and Um Jalul, should control the territories from the Nile to Lake Chad. Darfur, an independent Sultanate until just ninety years ago, lies in the centre of this land, with its fertile massif and access to the headwaters of the Salamat River. The Koreishi ideology, mobilized via a shadowy group known as the "Arab Alliance" or "Arab Gathering", motivates some of those involved in today's vicious war for Darfur.

Understanding this hideous violence demands a grasp of complex local histories that is possessed by few Sudanese and fewer foreigners. Generally relegated to a footnote of Sudanese history, as Gerard Prunier explains in Darfur: The ambiguous genocide, Darfur warrants its own political ethnography. Without this, it is not possible to understand the events of the past two years, nor the weighty moral and legal questions that surround them.

Darfur's is indeed an ambiguous genocide. Between 60,000 and 150,000 are said to have died during the crisis and some 2 million now live in camps. But the crudity of the violence obscures fine-grained particularities of motive that only make sense within the unique history of Darfur and its neighbours. Theirs is no centralized blueprint for racial annihilation, but rather a shading of different agendas and opportunistic alliances, facilitated by a cruelty that has become routine. The pivot of these is the Um Jalul, and its aspiring leaders' links with Chadian Arab militias, Libya's grandiose ambitions and -more recently - Khartoum's security cabal.

The Um Jalul are a clan of the Mahamid, who are in turn a section of the Abbala ("camel- herding") Rizeigat tribe of Northern Darfur and Chad. Their Bedouin roots can be traced back at least five centuries, when their patrilineal ancestors crossed the Libyan desert, entering Darfur from the north-west. The Abbala Rizeigat were thus in Darfur when the Fur Sultanate emerged in the early seventeenth century and a part of its bilingual Arab-Fur identity from the outset. In the mid-eighteenth century, the Sultan granted the Baggara ("cattle-herding") Rizeigat jurisdiction over a huge area of land south-east of the Sultanate's heartlands. Known as hawakir, such territorial grants are the basis of Darfur's land tenure today; who controls them is the subject of bitter political struggle. The Baggara's Abbala cousins, more mobile and living in the more densely administered northern lands, were less fortunate. Until today, many Abbala Rizeigat ascribe their role in the current conflict to the fact that they weren't given territory a quarter of a millennium ago. The Baggara Rizeigat by contrast are neutral.

Other Abbala also did not receive hawakir. After annexing Darfur on January 1,

1917 -almost the last territory to be added to the Empire -British colonial officials attempted to tidy up the confusion of Darfur's ethnic geography.

Another Northern Darfur Arab group, the Beni Hussein, were collected in one district over which they were given control. The Abbala Rizeigat had their eyes on a territory north of the region's centre; but the leading families of their two main sections -Mahamid (including Um Jalul) and Mahariya -could not agree on who should be paramount chief, or nazir. Since 1925, there have been at least six attempts to unify the different sections under a single leader. None has succeeded. One stratagem used by the rival sheikhs to increase their chances was to enlarge their numbers by attracting followers from Chad. The Um Jalul had an advantage here: there are more Mahamid than Mahariya clans in Chad, and in the 1970s the Chadian sections were armed by Libya and organized by Acyl. He enmeshed Darfur in Chad's racial war; and, pursuing his provincial ambition, Sheikh Hilal inadvertently led the Um Jalul into a maelstrom.

As we turn the political ethnographic lens, we find that the contours of Janjawiid mobilization correspond to the political fractures and family power struggles within the Abbala Rizeigat. Heads of Mahamid lineages have key positions, while most leading Mahariya families are uninvolved. Meanwhile a third section, the Ereigat, plays a different but equally critical role.