The story, a chilling tale of the plight of women under the now ousted Taliban regime, is rooted firmly in his country's traumatic past when women were suppressed and when images, be they paintings, photos or films, were banned.
Yet, for Barmak, Usama is also a movie about the future - a warning about extremism both to his own country and the rest of the world, and the promise of a new future for Afghan film making.
"I made Usama to tell the world to be careful about the future," the 41-year-old director and writer said.
"I really wanted to tell this not only for our people but also throughout the world because this is not only our pain. It is the human story and it should be told everywhere because, in my opinion, fanaticism and extremism belong not only to one religion, one culture. You can find it in different forms in every religion and every culture," he said.
Usama is the first entirely Afghan film shot since the rise and fall of the Taliban. It won the Golden Globe last month for the best foreign film and the Youth Jury Prize at Cannes.
Inspired by true story
Barmak's Usama has little to do with Usama bin Ladin, the fugitive al-Qaida leader held responsible for the 11 September 2001 attacks on the United States. It has a lot to do with a 12-year-old Afghan girl who is forced to cut her hair and live as a boy to help her widowed mother and grandmother survive in a world where women could not work and could not even leave the house without a male companion.
Called Usama, the girl-boy is rounded up with other boys to join a madrassa, or religious school, where she is soon betrayed by her own physiology, put on trial and forced to marry an elderly mullah.
"I really wanted to tell this not only for our people but also throughout the world because this is not only our pain. It is the human story because fanaticism and extremism belong not only to one religion, one culture"
The film was inspired by a true story which came to Barmak in his years as an exile in Pakistan after being forced to escape Afghanistan two weeks after the Taliban took control of Kabul in 1996. They were toppled by US-led forces in 2001 for harbouring bin Ladin's al-Qaida network.
As head of the Afghan Film Organisation before the rise of the Taliban, Barmak was one of Afghanistan's foremost film makers in a country that has produced fewer than 40 short or feature length films over the last 100 years. All of his own short films and documentaries were destroyed by the Taliban.
Yet, making Usama proved more difficult than merely finding - and repairing - the only suitable 35-mm camera in Afghanistan and raising finance, both with help from Iran.
Barmak scoured schools, refugee camps and orphanages in the summer of 2002 both for his protagonists and for dozens of extras, most of them women. The girl who plays Usama, Marina Golbahari, was found begging on a Kabul street.
After years of Taliban, Afghan
women's mentality 'has changed'
"After so many years of Taliban rule and also war, the mentality of these women was damaged. And when you talk about film, they think you are talking about Indian film with dance, song, romance and action.
"It took a long time to explain that I wanted to make a different film about their problems, their own personal stories and their pain. After many battles I succeeded in getting some people to play the parts. A lot of women are very poor and they came because of the pay. Also they got a good dinner and lunch," Barmak said.
The first public screening in Afghanistan, where a handful of cinemas still survive, was held in August. "The people loved this film. A lot of people told me they are feeling their own pain more after seeing Usama," he said.
Barmak said women's lives had improved dramatically since the fall of the Taliban, at least in cities where women now go to school, have their own political organisations and their own
press and radio stations.
But many rural women are still unable to read or write and lack health facilities, jobs and the means to feed their children.
Barmak, who has now re-established the Afghan Film Organisation, was invited to Los Angeles for the glitzy Golden Globes award ceremony in January, but he never expected his film to win.
"It was like a blast. I didn't know what to say on my way to the stage. But then I thought this is not only for me but for my people, for my country and for our future cinema.
"I was so happy for that. It is another opportunity for Afghan cinema. It means more film making, more optimism," he said.