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In addition to replicating the Osama bin Laden raid on the big screen, the big challenge in making "Zero Dark Thirty (2012)" was impersonating the real-life characters who were involved in the great hunt to the movie. Jessica Chastain opened up that she must tackle a very difficult task after getting cast as Maya, the strong female character who led the hunt of the al Qaeda leader.

"I had three months before we started shooting that I went to 'school' for it I guess," Chastain recalled. "I nicknamed [screenwriter] Mark [Boal] 'The Professor,' and I'd sit with him and go through the screenplay and ask a lot of questions about the character I was playing, about the CIA. I did some reading. Two books I found particularly helpful were 'The Looming Towers' and Michael Scheuer's book on Osama bin Laden."

The hard task got even more difficult because Chastain was unable to meet the real Maya in person. "Because I was never able to meet the real woman it's based on because she's an undercover agent, I had to use my imagination to fill in the blanks where the research couldn't answer the questions," she said. "Instead of going, 'Okay, Jessica Chastain as a CIA agent and this is what I would do,' I tried to answer why she was recruited out of school."

"Certain things that would be a reminder of the life she was becoming a stranger to, I had to create on my own, but still stay truthful to the woman I'm portraying," the red-haired actress continued. She added that the hardest part of impersonating Maya came as a result of Boal's script.

"There is a very definite arc for Maya, but the wonderful thing about her and actually the most difficult thing about her as an actor to play is she's someone who does not explain her subtext," the 35-year-old beauty explained. "She doesn't take the time to say how she feels. She doesn't like sit down and have a drink with someone and talk about her feelings. I mean, she's so haunted by this mission."

She went on, "A lot of the arc had to almost be mapped out before we even started shooting, so much so that I found chapters in the script that were marked by different ... for her when something might change. Is she brushing her hair? What kind of effort is she putting in when we see her, so we understand something about her before she even opens her mouth. So much of Maya is told without her explaining it."

Agreeing with Chastain, director Kathryn Bigelow acknowledged that bringing Maya to the big screen was not an easy job. She said that "it's a real testament to [Chatain's] talent that she could do that." Bigelow added that having a strong female character as the lead of her movie was like a bonus. "I think what's important to me is that this was a very strong character at the center of this hunt, and that the movie doesn't engage necessarily in gender politics about this character," she said.

"I mean, she is not defined by man, she is not defined by a love interest, she's defined by her actions, and I think that's a character that's very inspiring and is beautifully played by Jessica."

"Zero Dark Thirty" will expand to a wide release Stateside on January 11.