Angelina Jolie has taken to the stage at CinemaCon, the annual convention of theatre exhibitors, to reveal footage from the upcoming survival saga Unbroken, which she filmed in Australia.

“I wanted to make this film because its message is one that we all need now more than ever,” said Jolie in front of the crowd of theatre owners at the Caesars Palace in Las Vegas on Tuesday.

Shot in Sydney last year, the film tells the true story of Lou Zamperini, a World War II hero and track star who ran in the 1936 Berlin Olympics.

Zamperini, played by Jack O’Connell, spent a harrowing 47 days afloat in the Pacific Ocean following the 1943 crash of his US military plane. He spent the following two years as a prisoner of war after washing up behind Japanese enemy lines.

Developed originally by Universal Pictures in 1957, the biopic was supposed to star Tony Curtis, said Universal chairwoman Donna Langley, who introduced Jolie. But after many false starts, the project never took shape. It wasn’t until Zamperini’s story caught the attention of Jolie, that the film really began to evolve.

“She fought for it and earned the right to direct it,” said Langley, who called Jolie “a true filmmaker”.

Unbroken, to be released in December, is based on Laura Hillenbrand’s book Unbroken: A World War II Story of Survival, Resilience, and Redemption, which chronicles Zamperini’s life.

“Lou Zamperini is the toughest man I have ever met,” said Jolie.

“He’s a fighter and true hero. He is also a man of faith, full of love and humility. He sounds perfect. But he wasn’t always. Smoking, stealing and drinking by the time he was 9, he was convinced he was worth nothing and full of darkness.”

The footage revealed affecting scenes of Zamperini’s struggles, from his efforts to escape from his military plane after it crashed into the ocean, to the beatings he underwent as a prisoner.

Jolie added that Zamperini’s journey can remind us of what we’re capable of.

“Gain strength from our family, identify our fears and our pain, come face to face with darkness and never give up,” she said.

Unbroken is the second time Jolie has directed a feature. The 2011 war drama In the Land of Blood and Honey was her first.