Divorce is rarely unexpected, but it's never easy. This certainly holds for Sudan, where voters in the south are preparing to vote for or against secession from the north. But in geography, as in marriage, it's the terms of separation with the greatest potential for pain.
Registration for the January 9 referendum began yesterday and will continue through the month. Salva Kiir, the president of the semi-autonomous southern Sudan, called on his people to sign up "en masse" for the vote, and early indications suggest they intend to opt for secession in large numbers.
Juba's drive for self-determination comes after five years of relative calm in a dispute that spans decades and has left millions dead. There are many reasons it seeks a break with Khartoum, but in doing so it risks a return to hostilities. Southerners blame President Omar Bashir's government for political exclusion, and many are sceptical the north will accept the secession of the oil-rich south regardless of the vote.
There have been tentative moves towards reconciliation. Both sides agreed this week to a deal brokered by the African Union that addresses issues related to borders, economic activity and citizenship.
Demarcation of the border, 20 per cent of which is still contested, could prove the thorniest issue. While a resolution can technically wait until votes are cast in January, the longer the border remains in dispute, the more opportunity for violent clashes.
Troop build-ups on both sides of the border seem to be expecting trouble. For Sudan's war-torn western region of Darfur, the prospect that violence could spill over has worried peacekeepers who are already dealing with a humanitarian crisis.
Equally contentious are agreements over the distribution of oil wealth and the disputed region of Abyei. With reserves mostly in the south and refineries in the north, both sides stand to wreck their economic potential if they fail to find common ground.
The United States has joined the diplomatic effort, engaging Mr Bashir's government and offering to remove it from the list of state sponsors of terrorism. Senator John Kerry has personally called on both governments to come to agreement over Abyei.
The onus - and the decision - will remain in the hands of both sides. They have been separated for some time, and many think that a final divorce is inevitable. But regardless of what happens on January 9, they still must come to terms with their interdependence.