"Every day I think we all looked at each other and thought, How did he really survive this?" Angelina said.
Louis' survival story involves a plane crash, 47 days at sea and more than two years of torture in POW camps.
In February of this year, Angelina and Louis sat down with the TODAY show to chat about Unbroken. "[I feel] such a huge responsibility to get it right, because I love [Zamperini] so much, and because he's helped me so much in my life," Angelina said of the passion project. "[The world] can seem hopeless and it can seem very overwhelming. But the resilience and the strength of the human spirit is an extraordinary thing."
Angelina went through her own struggle in fighting for the directing job -- her second after In the Land of Blood and Honey. The Oscar winner told People that although she was up for the job, she was not a shoo-in.
"I had to pitch really hard," she recalled. "I was on fire. There was no stopping me. I was completely insane."
Sadly, Louis passed away in July at the age of 97. Before he died, Angelina was able to give him a special screening of the movie in his hospital room.
"Louis' story brings people together to push themselves to be their best," Angelina said. "I feel like that's what we gotta do for Louis."
With a script rewritten by Oscar winners Joel and Ethan Coen (No Country for Old Men), Unbroken, based on the book Unbroken: A World War II Story of Survival, Resilience and Redemption by Laura Hillenbrand (Seabiscuit), hits theaters Christmas Day.