By Ishbel Matheson
BBC News, Nairobi
With the Sudanese government and southern rebels signing up to peace on Sunday, they have brought the curtain down on Africa's longest civil war.
The conflict, which has lasted for two decades, has left the south in ruins.
There is optimism that peace in the south can finally hold
The battle has been about race, religion and resources. Africans from the Christian and animist south have long complained of discrimination by the Islamic government in Khartoum.
The United Nations estimates that the war has cost the lives of 1.5 million people. They died either because of fighting, or because of deprivation associated with war.
Four million people are believed to have fled their homes. Many of those who remained were cut off from the outside world.
A visitor to some parts of southern Sudan may wonder whether they are still in the 21st Century. When I went to the bitterly contested area of Western Upper Nile in mid-2001 there were no roads - either tarred or dirt. Travel was on foot, through marshy land of the Nile delta.
I saw one plough, donated by an aid agency. But it was being used as a bench, in the shade of an acacia tree. No-one knew how to train oxen to pull the plough.
The one health clinic, run by an aid agency, was many kilometres away. There were no schools.
In the distance, we could hear the muffled boom of powerful mortars. Rebel soldiers passed us, Kalashnikovs slung over their shoulders, hurrying up to the front-line.
US role in peace
Three-and-a-half years ago, the battle for the rich, oil reserves beneath the soil of Western Upper Nile was in full swing.
Now, the bitter enemies are setting aside their differences to sign a landmark peace deal, which should mean a fresh start.
So what brought the two sides to this historic juncture? The sustained diplomacy of the Bush administration has been crucial, particularly after the 11 September 2001 attacks in the US.
Can John Garang make a successful transition to government?
US officials portray their government's involvement as an "honest broker". It wants to see this vast and strategically important African nation back in the fold, after Khartoum's swing towards extremism in the 1990s.
Then, the government of President Omar al-Bashir was giving sanctuary to notables like Carlos the Jackal, and Osama Bin Laden.
Oil is also a factor. The US is searching for alternatives to its Middle East suppliers, and Sudan pumps up to 320,000 barrels per day.
US sanctions forbid business with Sudan. But the lifting of sanctions without a north-south deal would have been unacceptable to the religious right in America. These activists have adopted the perceived persecution of Christians in the south as a high-level cause.
The vigorous US diplomacy has also been matched by changing attitudes in Khartoum. The radical form of Islam promoted in the 1990s is in retreat.
As you walk around the capital, you have the impression of a city opening up to the world again, after years of isolation.
New office blocks are being built, as are conference centres and hotels. Korean cars nip around the streets. A few Western-style coffee-shops, offering fine cappuccino and ice-cream, are opening up. The Sudanese, it seems, want to shake off their image as a pariah nation.
Politically, too, the peace deal is good for the ruling clique of President Bashir. His potentially fragile position was highlighted by claims of a coup plot against him last year. But under the peace deal, Mr Bashir's position as head of state is entrenched.
The peace agreement also opens up historic opportunities for the southern rebels.
The veteran leader of the Sudan People's Liberation Army (SPLA), John Garang, will become the first vice-president. There will be a government of national unity, while the rebels will take charge of a semi-autonomous administration in the south.
The revenue from Sudanese oil, will be split 50-50 between the national government and the southern administration. Crucially, at the end of a six year interim period, there will be a referendum on southern independence.
Many southerners say if the vote was held tomorrow, the south would vote for freedom.
Mr Garang favours a unified but decentralised state. The challenge for his leadership will be to persuade his people that that they have a stake in a united Sudan.
He will also have the formidable task of transforming his rebel army into a government based on transparency and democracy.
Other African leaders have failed to make that transition.
As vice-president, Mr Garang may also be able to play an important role in calming the separate conflict in the western region of Darfur. He has already made it plain that he believes that war cannot be won by military means, only by negotiation.
With the signing of the peace deal in Kenya, a new chapter of Sudanese history is opening. Since independence in 1956, the country has known only 11 years of peace.
It is a time of optimism - but also trepidation. The previous peace deal between north and south collapsed in 1983 amid acrimony and accusations of double-dealing.
This time, the southern Sudanese are wondering, can peace last?