THE ageing Vietnam-era Huey helicopters came sweeping in off the mountains, dropping down on to the airfield outside the Afghan city of Jalalabad.

A handful of men, some armed with M4 carbine rifles and all wearing dark sunglasses, stepped onto the tarmac. None of them wore uniforms – only body armour – but they carried a certain military bearing about them, made all the more pronounced by their mysterious anonymity.

"Who are those guys?", I remember asking the American off-duty helicopter pilot sitting next to me smoking a cigar, that day a few years ago while I was embedded with the US military in eastern Afghanistan.

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"You don't want to know," the pilot replied with a smile, before slowly mouthing three staccato letters: C-I-A.

It wasn't the first time and would not be the last that I would encounter CIA operatives while working in Afghanistan. Some time later, while covering a story on the country's illegal heroin trade with the help of the US Drug Enforcement Administration (DEA), I would get a little glimpse of the more shadowy and covert activities that agencies like the CIA and DEA perform in Afghanistan.

It was, of course, only the tiniest of insights into what is otherwise a strictly closed and clandestine world.

Perhaps nowhere was that secrecy more rigorously applied than in what has been dubbed the greatest manhunt in history – the search for al-Qaeda leader Osama bin Laden. Now that hunt and the remarkable story behind it has been made into a feature film, which, though not due for release in the UK until early January, has already been tipped for Oscar success and stirred up a hornets' nest of controversy.

Dark Zero Thirty, which takes its names from a military term for 30 minutes after midnight or suggests some unspecified time between midnight and dawn, is an action thriller directed and co-produced by Kathryn Bigelow with a screenplay by Mark Boal, who both had previous Oscar wins with their powerful Iraq war drama, The Hurt Locker.

Driven to the point of obsession, a flame-haired female CIA analyst codenamed Maya, played by actress Jessica Chastain, will to some extent be a familiar type of CIA character for those of us – and there are many – who watch the Channel 4 television drama, Homeland.

However, where Maya in Dark Zero Thirty differs from Carrie – played by Claire Danes – in Homeland is that she is based on the real deal: a young CIA analyst who, while well-known for her work within the agency, today remains anonymous – in part, no doubt, for her own safety and security.

Long before Dark Zero Thirty hits cinemas, the arguments about its accuracy have stirred up all kinds of people from film critics and human rights workers, to security correspondents and CIA chiefs. At the heart of this controversy lies the film's depiction of torture.

The most vociferous of critics have gone as far as to call the director, Bigelow, a torture apologist. Such is the level of the row now ensuing that US Senators Carl Levin, Dianne Feinstein and John McCain last week wrote a letter to Michael Lynton, the chairman of Sony Pictures, accusing the studio of misrepresenting the facts and "perpetuating the myth that torture is effective."

Without creating a "spoiler" for the film, it's sufficient to say that in an extended opening sequence, Maya is present when a detainee is strung up by the wrists, stripped and sexually humiliated before being waterboarded and incarcerated in a coffin-like "confinement box".

What concerns critics of the film is that not only the discomfiting question – posed by The New Yorker magazine – that torture can be turned into "morally neutral entertainment", but that the film gives the misleading impression that torture led to the discovery of where bin Laden was hiding.

On Friday, the CIA itself took the curious step of issuing a statement to employees of the agency, which was posted on its website. "Dark Zero Thirty is a dramatisation, not a realistic portrayal of the facts," wrote acting director of the CIA Michael Morell, pointing out that the agency, "interacted with the filmmakers through our Office of Public Affairs but, as is true with any entertainment project with which we interact, we do not control the final product."

Leaping on this, critics also point out that the relationship between the filmmakers and the CIA was perhaps too cosy, given that Bigelow and Boal were given unprecedented access to agency advice, leaving many to conclude that they were inevitably over-influenced by the intelligence services' viewpoints and agenda.

One point on which there is agreement is that the film is certainly well made, described by many in the industry as stylish and inspirational in terms of technique from lighting, camera work and acting to the viscerally realistic production and costume design.

Another fascinating aspect to have emerged from the controversy surrounding Dark Zero Thirty has been the focus it has thrown on the role of women in the whole CIA hunt for bin Laden.

According to a Washington Post profile by Greg Miller, the CIA analyst who most resembles the real-life Maya is in her 30s and was in Pakistan as the hunt for bin Laden heated up in 2010. Having an almost Messianic devotion to her task, she takes no nonsense from her male colleagues. The Post profile, without naming the real-life analyst, says she was passed over for a promotion, and is an abrasive character who emailed colleagues saying they didn't deserve to share in a prestigious award she received for her role in capturing the mastermind of the 9/11 attacks on the US.

Peter Bergen, the celebrated CNN security correspondent and author who produced the first television interview with bin Laden, recently wrote of how from the establishment of the CIA's bin Laden unit in December 1995, by the agency's Michael Scheuer, female analysts played a key role in the hunt for al-Qaeda's leaders.

"(Female analysts) seem to have an exceptional knack for detail, for seeing patterns and understanding relationships, and they also, quite frankly, spend a great deal less time telling war stories, chatting and going outside for cigarettes than the boys. If I could have put up a sign saying, 'No boys need apply,' I would've done it," Scheuer told Bergen.

Another veteran CIA operative, Glenn Carle, who is now retired, says that when Scheuer set up the bin Laden unit the reaction among his fellow operations officers was, "What's his staff? It's all female. It was just widely discussed at the time that it's a bunch of chicks. So, the perspective was frankly condescending and dismissive. And Scheuer (and his staff) essentially were saying, 'You guys need to listen to us; this is really serious. This is a big deal, and people are going to die.' And of course they were right."

The women of the CIA bin Laden unit time and again contributed what is now clearly understood to be some of the most crucial intelligence and analysis, without which the al-Qaeda leader would never have been found. It comprised women like "Rebecca" (a pseudonym), who, in 2005, compiled a document titled Inroads that has been described as a vital guide that helped with tracking down the terrorist years after it was written.

As the controversy over Dark Zero Thirty reaches fever pitch, both director and writer Bigelow and Boal have come out fighting in defence of their depiction of the hunt for the world's most wanted man.

"The film doesn't have an agenda, and it doesn't judge. I wanted boots on the ground experience," Bigelow told journalists, while Boal has pointed out that "it's a movie, not a documentary", and that critics were "mischaracterising" the torture sequences. The films' critics remain unconvinced by such explanations, insisting it is has been constructed on a "grotesque lie".

That's an assessment agreed with by those who were close to the bin Laden operation, including the CIA's then director Leon Panetta and an FBI agent central to the hunt.

Pernicious propaganda, CIA hagiography or a movie that's simply had a bum rap and one that makes viewers come to grips with what former US Vice-President Dick Cheney euphemistically called the "dark side" of post-9/11 counterterrorism? Dark Zero Thirty has been called all of these things. British film audiences will have the chance to make up their own minds when the film hits cinemas early in the new year.