NEW YORK -- Kathryn Bigelow and Mark Boal were knee-deep in preparing the follow-up to their Oscar-winning "The Hurt Locker," a film that would chronicle the manhunt for Osama bin Laden, his escape in Tora Bora and the vanishing trail of the world's most wanted man.

"Then history changed," says Bigelow.

After a team of Navy SEALs killed bin Laden in his compound in Abbottabad, Pakistan, on May 2 last year, the director Bigelow and Boal, a journalist turned screenwriter, set about remaking their film. Whereas most films start with a concept or a dramatic arc, Boal and Bigelow built "Zero Dark Thirty" one source at a time, piecing together a narrative out of recent history shrouded in secrecy.

The approach -- a marriage of Boal's reporting and Bigelow's visceral action -- has made "Zero Dark Thirty" a lightning rod. The Academy Award-nominated film has spawned a Pentagon investigation and elicited op-eds that say the film exaggerates the efficacy of torture.

"Zero Dark Thirty," which introduces itself as "based on firsthand accounts of actual events," is a new kind of timely fusing of filmmaking and journalism -- what Bigelow calls "an imagistic version of living history."

Beginning with a black screen and a harrowing cacophony of voices from Sept. 11, "Zero Dark Thirty" unfolds like a decade-long revenge drama, depicting the sometimes ugly, sometimes cunning pursuit of bin Laden. The story isn't told through politicians or public sentiment, but via ferocious CIA officers (Academy Award-nominee Jessica Chastain, and Jason Clarke), modeled on the real if anonymous people -- the boots-on-the-ground -- who led the hunt.

"It's a movie about the work force," says Boal, who has spent time embedded with troops in Iraq and written articles for Rolling Stone and Playboy.

The film has stirred up considerable controversy, Some claim it's too journalistic -- that the filmmakers learned of confidential identities and details in their liaisons with the military.

It began when the conservative watchdog group Judicial Watch obtained records from the Defense Department and the CIA that detailed meetings in which Under Secretary of Defense for Intelligence Michael Vickers allegedly provided the identity of the commander of SEAL Team 6 -- the unit that killed bin Laden -- and of tactical planning on the raid. Homeland Security Committee Chairman Peter King, R-N.Y., then raised questions over the making of the film. The Pentagon and CIA have conducted internal investigations into the matter.

"If anything, I'm much more concerned than I was originally," says King, citing an ongoing investigation with the Defense Department. "People in the military were being pressured to cooperate with Hollywood and Hollywood was given access to areas of personnel it shouldn't have access to."

The White House has called the claims false. Defense Secretary Leon Panetta, the former CIA director who's played by James Gandolfini in the film, told the Senate in June that no unauthorized information was provided to the filmmakers.

Lt. Col. James Gregory, a Defense Department spokesman, said the hour-long meeting with Boal and Bigelow was part of a "system that has been in place for many, many years" to ensure Hollywood has the necessary background to represents the military accurately.

With her ninth film, the 61-year-old Bigelow seems to have -- in her collaboration with Boal -- found the subjects to match her long-held interest in violence and visceral storytelling.

In "Zero Dark Thirty" (the title is taken from the military term for 30 minutes after midnight, when the raid took place), obsessive tip gathering, brutal interrogations at "black sites" and high-tech geo-tracking culminate in a recreation of the raid in Abbottabad, for which a full-scale copy of bin Laden's compound was built in Jordan.

Scenes of torture have been one of the film's biggest talking points. Though CIA detainees have been said by Dianne Feinstein, head of the Senate Intelligence Committee, not to have played a part in the intelligence gathering that led to killing bin Laden, a detainee is shown in the film to help lead to identifying bin Laden's courier. 

The filmmakers hope the movie is seen as being straightforward and sans agenda -- an analytical history that asks the audience "to lean into their own conclusions," says Bigelow. The intended perspective, she says with relish, is: "On the ground, in the center of that hunt."

"What better place to be?" says Bigelow. "It's where I wanted to be. I wanted to put the audience right in the middle of it and keep it as subjective and immediate and visceral and primal as I possibly could."