They call them the "Lost Boys" -- a scattered generation of former child soldiers forced to fight or flee in south Sudan’s bitter two-decades-long civil war with the north.
Now they have grown up and have been returning to their homeland to join in the south’s historic independence vote which begins on Sunday.
"We are supporting the referendum for our freedom," said Valentino Achak Deng, holding out his voter registration card with pride. Deng’s story is perhaps one of the best known of all of the "Lost Boys" from the war -- his dramatic tale of survival as a child soldier in the war-torn south was written up by US author Dave Eggers in the best-selling book "What is the What".
As a boy, Deng trekked across the vast swamps and grasslands of the south to Ethiopia, as his friends were shot around him or died from wild animal attacks or starvation. Finally, after years in a desert refugee camp in Kenya, he was granted asylum in the United States in 2001. But he never forgot the south.
"This is an opportunity we must not let go to waste," said Deng, who is using the proceeds from the book to build a high school in his war-damaged home town.
His tale is extraordinary only outside Sudan -- in the south, such accounts of heroic survival and grim suffering can be told by all too many.
Some two million people died and four million fled their homes in that 22-year war with the north, a conflict fuelled by religion, ethnicity, ideology and resources, particularly oil.
Now those who have returned are determined the south will not have to face a war like that ever again.
"The referendum means everything to us," said Kur Ayuen, a south Sudanese-Australian who, like Deng, fled the war as a child and grew up in tough refugee camps in Kenya.
"I knew when the referendum was coming that I had to come back to give all the support that I can," the 32-year-old campaigner said.
Ayuen runs the My Referendum for Freedom pressure group, which has been working to boost education and awareness about the vote by organising street marches and concerts.
"We have been working to make sure the people first turned out to register, and now turn out to vote," he said.
Excitement has been rising for weeks amid the countdown to the week-long ballot, a key plank of the 2005 peace deal that ended Africa's longest-running civil war.
Most analysts expect the south to vote to break away and split the continent's largest nation in two.
Optimism is high.
"My children are still at school in Uganda, where I grew up during the war, but when the south is free, I will bring them back too," said Mary Nailo, a fruit trader.
"I am not expecting there to be immediate opportunities, but work and development will come from the peace of being free."
Those unable to return to the south for the referendum are still supporting it from outside.
More than 60,000 people have registered to vote in eight nations -- neighbouring Egypt, Ethiopia, Kenya and Uganda, as well as in Australia, Britain, Canada and the United States.
"This is a great moment in our history," said Lopez Lomong, who fled the south as a child when his village was destroyed, but who is now an athlete in the United States team.
Lomong, who carried the US flag in the opening ceremonies at the 2008 Olympic Games in Beijing, still also holds a strong flame for his original homeland.
"We are all of us looking forward to the referendum," said Lomong, speaking on a visit to the southern regional capital Juba in December, but who will vote in the United States. "I am wanting the south to be free."
Others have set up websites to promote the vote.
"We have both opportunity and obligation to make our dream for freedom come true," wrote Alex Yata Lukadi, a south Sudanese-Canadian, on a fund-raising website he set up to support the referendum.
But there are many returning from outside without those resources -- either from the north or from neighbouring nations.
Down at the river port in Juba, southerners arrive on slow barges having travelled up the White Nile from the north.
They are just a few of the 120,000 southerners who have come back home in the past two months, according to the United Nations refugee agency, after the flow doubled since mid-December.
"We heard the south was developing, so we came back," said Patience Achiro, who fled to the north during the war.
She currently lives in a makeshift plastic shelter with her four children, as she waits for onward transport to her village.
"Things are hard and there is not enough food to eat," she said. "But we are happy to be coming home."