“It’s not illogical, it’s just a miracle.”

When your subject matter is the life of Louis Zamperini, an American Olympian, prisoner of war survivor, record holder for the longest number of days adrift at sea and the subject of the movie Unbroken, these are the sorts of truths you hold dear.

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Producer Matthew Baer calls them “the miracles”. The events that formed the extraordinary, quite unbelievable beats of Zamperini’s life. In fact he laughs at a report that some audience members found moments in the film tough to believe at the Sydney premiere on Monday night.

“Yeah, but it happened! I understand that would have an absurd quality to it, but so much of Lou’s story is the stuff of ‘if it wasn’t true then you wouldn’t dare to put it in a film’.”

Amid the adoring chaos brought about by her arrival with husband Brad Pitt for the premiere, director Angelina Jolie reeled them off on the red carpet: “Two plane crashes, 47 days at sea, the 1936 Olympics. It’s hard not to make it cinematic.”

The superstar actress – but only second-time director – excels in doing so, but it was anything but easy, even if Jolie graciously credits Australia with much of the work. “The challenge was to capture that on film, within our budget, being able to get it right. We needed to have a country like this where we could come and have that scope and that variety of location.”

To get a sense of how big a project this is, what a miracle it is that it has even made it to the screen, one has to travel back in time.

Universal Pictures bought the rights to Zamperini’s memoir Devil at My Heels in 1956 with Tony Curtis set to play the Olympian-turned-prisoner-of-war. When Curtis’ career took off with Spartacus, Zamperini’s project was forgotten. It never even made it to scripting.

In 1998, Baer took up the rights after seeing a documentary about Zamperini. In the flurry of excitement that ensued Zamperini was set to be played by Nicholas Cage but the script and scope proved daunting. Baer explains: “In truth the story hasn’t changed since 1950. It’s the same situations that happened. But it’s an embarrassment of riches in terms of how much story you can tell.”

While others fell away, Baer would not be stopped and spent more than a decade shopping the script around Hollywood, to the point that when Jolie mentioned the project to Pitt, he replied: “Oh honey, that’s been around forever.”

Things had changed, however, with the release of a new bestselling biography, Unbroken, by Laura Hillenbrand – author of Seabiscuit – in 2010 and Jolie resonated with Zamperini’s tale. Once she came on board, things got serious.

“Having Angelina makes anything easier,” says Baer. “It was really about having a director who was able to push the boulder up the hill at a major studio with a significant project and who had a very clear vision for what she wanted as a film maker.”

Jolie wanted to cast relative unknowns in the lead roles. Jack O’Connell took on the mantle shirked by Curtis and Cage. Japanese pop star Miyavi became the villainous concentration camp commander after he was cajoled into his first acting performance by Jolie backstage at one of his concerts. The big names were saved for the script. The Oscar-winning directors, the Coen brothers.

“One of their son’s had read the book,” says Baer of yet another Unbroken piece of fortune.

“They viewed the assignment as a good opportunity for them to write something that they didn’t have to direct. So it was done in the spirit of ‘ok you go and do this because it is so much larger than we would be interested in doing’.

“As a result of that, they said from the start: ‘we didn’t say we’re going to deliver you the small version of Unbroken, we’re going to deliver you the big version of Unbroken’, and that’s what they did from page one of the movie.”

The Coens cracked the script problem by starting with one of Baer’s miracles – an air battle Zamperini survives despite his plane finishing with 500 bullet holes – then cutting back to his childhood in church, allowing the film to properly pay service to Zamperini’s later life conversion to Christianity without actually including it.

Baer suspects the moments of faith could equally be jarring to some audience members. “Joel and Ethan were very interested in the spiritual aspect of the story, which was also surprising but very true. There hasn’t been a mainstream studio movie in years that is so faith supportive.”

Again, though, they wouldn’t and couldn’t be included if they weren’t true. Baer is boosted through the exhaustive research by Hillenbrand. “It’s not just Lou telling stories. Those kind of small miracles are weaved throughout the story.”

While any of the “miracles” viewed out of context feel cliched and unlikely, as a whole they form a tapestry both convincingly sincere and impressive to behold.

For Jolie, that is ultimately down to one man.

“Everybody loved Louie so much,” she says. “Most everybody who worked on the film spent time in his house sitting and talking to him. So we all had this ‘Oh my God, we better do right by this man’. He became like a father to us and we weren’t going to let him down. So everybody worked very, very hard.”