The horrors in Darfur mark this century's first great venture in genocide, but they are not the first such action perpetrated by the National Islamic Front (NIF) regime ruling Sudan. That distinction goes to the jihad directed against the various African peoples of the Nuba Mountains beginning in 1992. Genocide began again in the vast oil concessions of southern Sudan in 1998, when the African peoples of the region became targets of a systematic policy of scorched-earth clearances. Many hundreds of thousands were killed or displaced.

Khartoum's genocide in Darfur is both familiar and different. It is, as seasoned Sudan analyst Alex de Waal has argued, "the routine cruelty of a security cabal, its humanity withered by years in power: it is genocide by force of habit." Confronted with a surprisingly robust military insurgency in Darfur -- growing out of decades of economic marginalization and a near-total breakdown in civilian security -- the government in Khartoum instinctively responded by organizing and deploying the Janjaweed Arab militia, which has brutally and systematically destroyed the means of agricultural production throughout Darfur, focusing almost exclusively on African tribal groups. These people now confront "conditions of life calculated to bring about their physical destruction": They face genocide.

No reasonable world order can tolerate a serially genocidal regime that rules only by virtue of ruthless survivalism. Yet this is what the United Nations appears prepared to do. A July 30 U.N. Security Council resolution on Darfur was an exercise in temporizing. Veto-wielding China and Russia, as well as Pakistan and Algeria, resisted all meaningful action; both China and Pakistan abstained in the final vote, signaling that nothing further will be done when the Security Council takes up Darfur again on Sunday.

In the distorting shadow of the Iraq war, this is an exceedingly difficult moment to argue for "regime change" in Khartoum. But regime change alone can end genocide as the domestic security policy of choice in Sudan. And it is the only thing that can avert the deaths of hundreds of thousands in Darfur. The mismatch between humanitarian need and capacity grows more deadly each day. And Khartoum is strenuously resisting deployment of any peacekeeping force, even from the African Union.

The moral logic of regime change could not be clearer. The NIF came to power by military coup in 1989, deposing an elected government and aborting the most promising peace process since Sudan's independence in 1956. The only arguments against regime change are those of realpolitik (the regime is Sudan's de facto government) and practicability (how can Sudan's governance be taken into international receivership?).

But years in power cannot legitimize genocide: This will only encourage regimes like Khartoum's to believe they are invulnerable and act accordingly. Even from the realpolitik perspective, acceptance of rule by those who commit genocide is counterproductive to regional and world order; it also offers encouragement to other regimes tempted to use genocide as a political weapon.

To the second objection -- how will it be done? -- there are certainly no easy answers. But one consequence of the Iraq war (though of course not a justification in itself) is that public discussion of regime change by the United States will resonate much more deeply in Khartoum's despotic thinking. If it is coupled with serious efforts to work with our European allies to squeeze Khartoum by means of comprehensive economic sanctions, as well as sanctions targeted against NIF leaders, we may first be able to secure a permissive environment for humanitarian intervention in Darfur, saving hundreds of thousands of lives.

If regime change is not to be chaotic, it must be organized by a consortium of international actors, including regional governments; efforts must be made to reach out to all opposition parties throughout the country and in exile. A proportionately representative interim governing council must be created externally but be ready to move quickly to take control when the NIF is removed by whatever means are necessary. The great risk is an implosion of the military that sustains NIF power, but this risk is as great without any effort of regime change.

The challenges adumbrated here are daunting and politically risky. The consequences of failing to accept these challenges are continuation of genocidal rule and additional hundreds of thousands of deaths.

The writer is a professor at Smith College.