However opportunistic, the Khartoum- Janjawiid alliance proved an effective machine for devastation. Between February and August 2003, the SLA's mobile forces ran rings around inept Government garrisons; Khartoum's response was a merciless campaign of assault by militia and air force. Janjawiid brigades now became Military Intelligence's strike force, allowed to promote whatever local agenda they saw fit, provided they contained the rebellion. It worked, at hideous human cost. By early 2004, the SLA was losing ground, and later rebel offensives into Eastern and Southern Darfur were halted, using similar tactics.

Since the beginning of this year, the level of organized violence has dropped dramatically, but half of Darfur's people are confined indefinitely to displaced persons' camps.

Lacking local knowledge about what is actually driving the Darfur conflict, many have given it their own spin, particularly over the notion of "genocide".

Both its diagnosis and reaction to it are fraught with ambiguity. One approach was followed by the United States Government. Following a Congressional resolution in May 2004, the State Department dispatched a team of investigators to refugee camps in Chad to ascertain whether the Sudan Government was committing genocide. On September 9, Secretary of State Colin Powell reported, "genocide has been committed in Darfur and that the government of Sudan and the Jingaweit (sic) bear responsibility and genocide may still be occurring". In international law, a determination of genocide should demonstrate both that a crime is committed that fits the definition in the 1948 Genocide Convention (actus reus) and also specific intent on the part of the perpetrator (mens rea) "to destroy, in whole or part, a national, ethnical, racial or religious group". Powell had good evidence for a pattern of atrocities that looked like genocide. He had no proof of intent. But to equivocate -as his predecessor, Madeleine Albright, had done over Rwanda a decade earlier - risked being pilloried. State Department lawyers were encouraged by the reasoning of the International Criminal Tribunal for Rwanda. Faced with the problem of proving genocidal intentions when the accused denied them, the tribunal's judges ruled that it was legitimate to infer intent from the "general context" of extreme violence directed against a group. Another good reason for making this inference is that it is almost impossible to reach a conclusion about genocide while it is actually occurring, meaning that the Genocide Convention would only be good for prosecutions after the fact. Powell's phrasing was, however, curiously passive. He did not say that Khartoum's leaders and their militia were genocidal criminals; in the next breath he said that US policy would not change.

A different approach to determining genocide was adopted by the International Commission of Inquiry into Darfur, set up by the United Nations Security Council, which reported in January 2005. The ICID detailed the same pattern of abuses as in the State Department report. "However", it continued, the crucial element of genocidal intent appears to be missing, at least as far as the central Government authorities are concerned. Generally speaking the policy of attacking, killing and forcibly displacing members of some tribes does not evince a specific intent to annihilate, in whole or in part, a group. Rather it would seem that those who planned and organized attacks on villages pursued the intent to drive the victims from their homes, primarily for the purposes of counter-insurgency warfare.

In short, the killings in Darfur looked like genocide but were actually a by-product of defeating the rebellion. The Commissioners, all of them veteran independent human-rights specialists, had shied away from the fence that the Americans had so readily jumped. But the Khartoum Government -despite trumpeting the "no genocide" finding -could take no solace from a report that found that "the crimes against humanity and war crimes that have been committed in Darfur may be no less serious and heinous than genocide", and which noted that individuals -including Government officials -may have possessed genocidal intent. Unlike Powell, the ICID recommended a specific course of action, namely referral to the International Criminal Court. In March, the US set aside its long-standing opposition to the ICC, and allowed the Security Council to refer the Darfur case to The Hague. The prosecutor is currently examining a sealed list of fifty-one individuals identified by the ICID. Although indictments are many months away, the prospect of extradition to face prosecution has prompted a shiver of fear among Khartoum's security chiefs. The blades are whirring just behind them.

The ICID determination is based on a higher standard of proof than that of the State Department. It is open to complex legal dispute; much hinges on primary purpose and double effect. Could it not be argued that genocide is a predictable corollary of counter-insurgency conducted in a certain manner? And is there not reason enough to deduce as much from the previous two decades of warfare in Sudan -and indeed from other modern wars? On the other hand, the 1948 Convention identifies genocidal intent in a precise way, and hard legal work needs to be done if that is to be broadened to include genocidal outcomes as a secondary impact of other aims.

By the time the ICID began its work, Sudan Government Military Intelligence and the Janjawiid had largely completed theirs. Mass murder and burning had been replaced by pervasive fear that kept Darfur's two million displaced people and refugees in their places of exile. African Union ceasefire observers were on the ground, along with an array of international humanitarian agencies. As a result, the ICID's main brief was to identify the scope of the crimes and the individuals responsible. As the Hague Tribunal for Former Yugoslavia has shown, the most effective way to prosecute crimes of genocide is to begin with multiple instances of mass murder and group-directed war crimes and then to deduce that these cumulatively amount to genocide. Both empirically and legally, the ICID took a serious and thoughtful position, which will doubtless be scrutinized and contested as the ICC goes about its work.

Prunier, however, has no truck with such nuance. He opens his discussion by characterizing the ICID report as part of "a coordinated show of egregious disingenuousness". "The semantic play", he writes, "ended up being an evasion of reality. The notion that this was probably not a 'genocide' in the most strict sense of the word seemed to satisfy the Commission that things were not too serious after all." Given the subtitle of his Darfur and Prunier's previous work on the Rwanda genocide, this is a disappointingly inadequate conclusion.

After the question of genocide, the most controversial issue in Darfur is the death rate. The question of how many people have died is important, but desktop demography is hazardous when the methods of data collection are varied and have not been fully scrutinized. Prunier is not alone in hinging strong claims on the fact that, in one survey of refugees, 61 per cent said that they had seen a "family member" killed. As a general index of horror this is a compelling statistic. But it is impossible to make any numerical inference until one knows what the investigators meant by "family". Demographers distinguish the household (usually defined as those who eat together daily, and usually used as the unit of enumeration) from the family, which commonly stretches far wider than those five or six individuals. Until there is a thorough population-based survey of mortality in Darfur, all estimates for deaths from violence, disease and hunger will remain conjecture.

Prunier has some good sources but often treats them casually. In his catalogue of international neglect of the conflict he says that Justice Africa failed to mention Darfur in its October 2003 briefing. There were in fact four paragraphs that month on Darfur, which had been covered in every issue of the briefing since March, including a warning on May 27 that the strategy of "arming local militia" would, if followed, "run the risk of creating a vicious internecine war targeting civilians". Prunier does provide a competent sketch of the history of Darfur and the position of the conflict within the politics of Sudan and the region. And his account is valuable in locating Darfur within the politics of the Central Sahara and the long-running three-cornered wars between Libya, Chad and Sudan. He correctly describes pre-colonial Darfur as an "ethnic mosaic" rather than a region with a binary polarized "Arab"-"African" identity divide. He notes the ambiguity of the term "Arab" (though he doesn't explore the varieties of Arabism); he makes useful points on the politics of the Umma Party, the main party in the ruling coalition toppled by the current Sudan Government, and the Darfur Development Front in the 1960s and 80s and on Libyan-Sudanese relations in the 1970s and 80s.

Errors and omissions are inevitable in any analytical narrative of Darfur; but Prunier omits entirely the central protagonists. He is also too sweeping in his account of the role of international mediation in Sudan. International efforts to find a solution to Darfur's agony are now in the hands of the African Union, which Prunier dismisses as "the politically correct way of saying 'We do not really care'". But American, British and other international support to the Kenyan-headed North-South peace process followed a similar formula of ad hoc multilateralism, and did bring an end to twenty years of comparably vicious war. Darfur's peace process is in some respects more challenging. Having sealed its big win in the North-South peace, the Sudan Government is playing for tactical advantage while the rebel leadership is deeply divided. The political issues that divide the belligerents have yet to be thrashed out; the agenda for negotiations is itself a matter of acrimony.