BOSTON — Is anyone surprised that the Sudan government violently seized Abyei?

For months there have been warnings of a military buildup, particularly by the Sudan Armed Forces to the north, of troops, tanks and heavy armaments. President Omar al-Bashir's regime in Khartoum refused to give up its claims on Abyei with its fertile pastures and productive oil fields.

The oil is what this is all about. Abyei's oil is the largest source of wealth for Bashir's government. It is why Bashir fought a bitter 22-year war — in which some 2 million people died — to prevent the South from seceding from the North.

Let's not forget the regime we're talking about. Bashir is already indicted for war crimes by the International Criminal Court for the flagrant violence his Janjaweed militias inflicted for years in the Darfur region of western Sudan. It is estimated that as many as 400,000 have died and 2.5 million have been displaced by that violence.

Bashir is unapologetic and defiant over Darfur. Why would anyone expect him to be reasonable over Abyei and South Sudan?

At the same time the Bashir regime seized Abyei, it stepped up bombings in Darfur and its support for ethnic militias in the South.

Bashir accepted the results of the January referendum in which the South voted for independence. But, significantly, he did not give up his claims to Abyei. He massed troops and tanks near the border.

Khartoum's army, the Sudan Armed Forces, was in place and over the weekend used the pretext of a small attack by the southern forces of the SPLA on a U.N.-escorted convoy to indiscriminately bombard and occupy the Abyei region.

Now that Abyei has been seized, Bashir will present South Sudan and the international community with a fait accompli. The North holds Abyei and its oilfields and will, perhaps, negotiate to allow a dribble of the petroleum earnings to go to the barren South.

GlobalPost's Tristan McConnell warned against this after visiting Abyei in January.

"It all hinges on Abyei," said George Clooney, about the independence and economic viability of South Sudan after several visits to the disputed border area.

Clooney launched the innovative Satellite Sentinel Project to focus the world's attention on Abyei. It was hoped the evidence of a military building would prevent the United Nations from turning a blind eye to the situation and it would send in enough peacekeeping troops to prevent to prevent any aggressive action.

The satellite photos proved there was a military buildup. Then there were the ominous attacks on a few small villages in the border area. Many urged the U.N. to send a peacekeeping force into the border area between North and South Sudan.

But the U.N. was already embroiled in the nasty fighting in Ivory Coast and the world's attention was focused on the Arab Spring, the Libyan war and the ongoing tumult in Yemen and Syria. No preventive measures were taken. And so Bashir's tanks just rolled in and took Abyei.

What's at stake?

Plenty. The South Sudanese have declared the seizure of Abyei an "act of war" and this is not just rhetoric. There is a real risk that Sudan will be plunged back into war over the issue of Abyei.

What can be done?

The United States and the United Nations must take decisive action.

The U.S. must demand the immediate withdrawal of the Sudan Armed Forces from the Abyei area. The U.S. must immediately suspend the process to normalize relations with Bashir's Sudan. It must halt movement to review Sudan's status as a state sponsor of terror. All steps toward debt relief and the lifting of sanctions must also be stopped. The U.N. Security Council must speed up plans to protect civilians from violence.

“If there is no cost to the Khartoum regime’s commission of atrocities and to the dishonoring of agreements, then why would anything change in Sudan?” said John Prendergast, co-founder of anti-genocide group, the Enough Project. “Darfur is deteriorating, Abyei is a war zone, and pockets of the South have been set aflame by Khartoum-supported militias. It is time to impose serious consequences for the Khartoum regime’s use of overwhelming military force to deal with every challenge it faces.”

There is an issue that needs to be resolved over Abyei. It is the question of the nomadic people who travel in and out of the Abyei region. If the Miseriya people vote in Abyei, then many say the region would vote to stay with the Khartoum regime rather than to join the South in independence. This is an issue that should be resolved by negotiation not by tanks rolling through the plains of Abyei.

Less than two months from the independence of South Sudan, the efforts to negotiate the status of Abyei have been dashed by the North's military occupation. The U.S., the U.N. and the international community must press the Bashir regime to withdraw and resume negotiations over the strategic Abyei region. Only if that key issue is resolved can South Sudan begin its independence with an outlook for a stable and prosperous future.