Khartoum's hostilities along Africa's newest border threaten to create a hard division between the two Sudan's, which would harm the interests of both sides.
Abyei attack signals a hard border that is bad for both sides
Only a month remains until South Sudan's independence on July 9, and the prospect of future good relations between the two successor states of Sudan is rapidly diminishing.
As in other territorial divorces, the list of issues to be resolved is long and complicated. But with the recent explosion of violence in Abyei, contested elections in Southern Kordofan and disputes over the redeployment of military forces, Sudan's north-south borderlands have come front and centre.
A failure to manage the world's newest international frontier, which at more than 2,000 kilometres is Africa's longest, risks perpetuating chronic instability between the two Sudans, even as millions continue to depend on trade links, migratory routes and access to grazing lands on both sides of the border.
On May 21, Khartoum sent jets, tanks and a division-strength army to invade the Abyei area, a disputed territory about the size of Qatar, nestled on the border between north and south Sudan.
Control of Abyei has been disputed throughout the implementation of the 2005 Comprehensive Peace Agreement (CPA), the deal which permits the south to become an independent country.
The CPA states that Abyei is part of northern Sudan until a referendum of its residents determines otherwise. But the government of Sudan's military occupation of Abyei is a clear violation of its CPA commitments, which required the effective demilitarisation of the district outside of special joint north-south units.
The referendum vote had already been postponed indefinitely, due to long-running disputes over voter eligibility. And with almost the entirety of Abyei's population displaced, a vote would presently be impossible, even if the parties could find agreement on delivering a ballot.
The immediate cause of Khartoum's occupation was an attack by southern Sudanese military forces on a northern army convoy moving troops out of Abyei on May 19.
But as with Gavrilo Princip's assassination of Austrian Archduke Franz Ferdinand in the run-up to the First World War, the explosive cocktail of ingredients had already been mixed well in advance of the final spark.
Khartoum's counter-attack was long planned and smoothly executed. Elements of the army's 14th and 15th divisions were ready to move and put their attack plans into operation far more quickly than the South could have anticipated.
Both sides have violated international law. However, while the south Sudan military attack on the northern convoy doesn't appear to have been sanctioned by the high command in Juba, orders for Khartoum's invasion of Abyei did come straight from the top.
The systematic destruction and looting of Abyei town, for the second time in three years, was calculated and deliberate. The resulting displacement of tens of thousands of civilians was intentional, and Khartoum is in no hurry to welcome these citizens back.
Amid reports of resettlement, a demographically altered Abyei would not displease the government of Sudan.
International actors underestimated the popularity of the occupation of Abyei in Khartoum, still reeling from the blow to national prestige that is South Sudan's secession.
It was predictable that President Omar al Bashir would be outraged by an attack on his Sudanese armed forces. Had an attack on the army gone unanswered, questions would have been raised about the morale of the forces - and more importantly, of the regime generally. Yet the convoy incident hastened the Abyei incursion by a few weeks at most.
A return to all-out war between north and south is unlikely. But ongoing destabilising internecine conflict in the borderlands is all too possible, in areas neither side is able to police or manage effectively.
The current post-election violence in Southern Kordofan - directly contiguous to Abyei - demonstrates worrying signs beyond the tiny enclave, as threats escalate and the prospect of a rigid border increases.
In Sudan's case, good fences would not make good neighbours. In fact, a hardened border would be disastrous. It would throw the lives of millions who depend on cross-border relations into uncertainty. It would be economically ruinous for citizens of both sides. It would disrupt the movement of hundreds of thousands of pastoralists who migrate seasonally in search of grazing land, as they have done for generations.
A hardened border would be impossible to impose effectively and would be counterproductive in many matters of cross-border interest: land, water, oil and transport among the most critical issues on the list.
The invasion of Abyei is an occupation on two levels. Most obvious is the brutality of indiscriminate armed violence deployed against civilians. But the invasion also represents the imposition of a hardline approach for the management of Sudan's unresolved disputes, the sort of occupation that crowds out compromise and respect for existing agreements and peaceful means for finding resolution.
South Sudan considers its forthcoming independence from the north as bringing a final freedom from tyranny.
But millions in the borderlands will still be subject to the destructive impulses of both capitals, which may only be exacerbated further in Sudan's two-state future.
Aly Verjee is a senior researcher at the Rift Valley Institute, specialising in the politics of eastern Africa