We have no way of knowing exactly how many have fled in South Kordofan but the estimates are growing with terrifying speed; the UN estimate for the capital of South Kordofan State, Kadugli, is around 40,000. Human Rights Watch reports “tens of thousands of people” fleeing toward El Obeid, the capital of the North Kordofan State. The World Council of Churches, an organization with close ties to the people of the Nuba, reports that as many as 300,000 civilians are besieged and cut off from humanitarian assistance. The highly reliable Sudan Ecumenical Council has declared that “[other civilians] have fled to the Nuba Mountains, where they are being hunted down like animals by helicopter gunships.” With critical shortages of water and food already reported—it is also now the “hunger gap,” the period between fall and winter harvests and the next round of harvests beginning in October—conditions for those who have fled and are cut-off from any assistance will only grow more deadly.

Ominously, Sudanese President Omar al-Bashir has given a free hand to military forces in South Kordofan, apparently giving license for the persecution of anyone accused of sympathizing with the southern Sudanese movement and party, the Sudan People’s Liberation Movement (SPLM), which is overwhelmingly made up of African tribal groups. Human Rights Watch reports receiving “credible reports” that various northern militia “carried out house-to-house searches and set up checkpoints,” killing civilians in the process.

While the immediate impetus for the violence in South Kordofan is unclear, there is evidence that the assaults were viciously premeditated. Reports from groups like the Small Arms Survey going back to October 2010 have indicated that the build-up of regular military forces and ethnic militias has been massive, and was undertaken with clear ambitions. The regime’s primary military base outside Khartoum lies just north of South Kordofan, but connects by road to Kadugli, putting advanced military jet aircraft within easy flying distance of the Nuba Mountains. (Only Khartoum has military aircraft.)

But alarmingly, it’s not yet clear whether the Obama administration appreciates the enormous differences between South Kordofan and Abyei, and in particular the potential not just for ethnic clearances but large-scale ethnic destruction. Khartoum had exerted de facto military control over Abyei for several months, and there was little chance the Southern SPLA would respond militarily. But those Nuba who are members of the SPLA feel that in fighting they will be defending their homeland, and their resistance will be intense.

The administration’s response to the seizure of Abyei was far too muted and lacked a clear articulation of specific consequences if Khartoum failed to abide by a UN Security Council “demand” that the regime withdraw militarily. This had the disastrous effect of encouraging Khartoum to believe that there would be an even less forceful response to military action in South Kordofan, which, unlike Abyei, is geographically clearly in the north.