In 1972, at the height of the Troubles, the Irish Republican Army allowed an American TV crew to film its members as they engaged in weapons training, patrols, gun battles and bombing missions across Northern Ireland. The operations were real, not staged, and senior commanders appeared on camera without concealment. The TV crew shadowed one unit as it packed a car with explosives, drove it into the centre of Derry and detonated the bomb, injuring 26 people. Europe’s deadliest guerrilla force had declared 1972 the year of victory and wanted it captured on film. The result was a propaganda documentary, The Secret Army, that was intended for American audiences. It showed remarkable scenes never seen before or since – the nuts and bolts of how IRA men and women went about planning and unleashing mayhem, and what they thought about it. But the story behind the film, it turns out, is even more extraordinary than what appeared on screen. The US production tangled Martin McGuinness, British intelligence, the CIA, a Nazi hunter and Muammar Gaddafi in a strange web of intrigue – and then the film vanished, largely unseen and forgotten, for almost 50 years. Now, for the first time, the story behind the story has been told. A BBC documentary has pieced together a tale with more plot twists than Argo. Titled The Secret Army, it investigates the film of the same name through a twisting trail of evidence from Belfast and Derry to London, New York, Boston and Arizona. “Despite the passage of over 50 years, we tried to find the pieces of the puzzle to reveal how this documentary was made,” said Darragh MacIntyre, a reporter for BBC Northern Ireland’s current affairs team. Finding anyone still alive who knew how the film was made and why the IRA consented was a challenge, said John O’Kane, a producer: “It was all shrouded in mystery. In peeling back the layers of this story we’ve discovered something that is much more complicated than we imagined.” The central figure is J Bowyer Bell, a New York-based historian who published a book, The Secret Army: the IRA 1916-1970, as the Troubles erupted. Based on archives and interviews, it was well-received and established Bell’s credentials with republicans. He persuaded the IRA to participate in a documentary filmed by a hand-picked team from the US. Over several months in 1972 the crew filmed IRA members as they learned about guns and bomb-making and applied their lethal skills in the streets of Belfast and Derry. It received a modest premiere in a New York pub – an Irish Times correspondent wrote it up in an article headlined “Not-so-secret army filmed” – but Bell was eying TV networks and a theatrical release. He was to be disappointed. Walter Cronkite’s CBS Evening News show ran some clips, but otherwise networks shunned the film and it largely disappeared from public view. “I showed it to Viacom; they loved it,” Leon Gildin, a co-producer, told MacIntyre. “They offered me a contract for worldwide rights. What happened after that? Viacom took the worldwide rights and never sold a copy.” Bell believed British intelligence persuaded authorities to stifle his film. Another theory is that escalating bloodshed in Northern Ireland unnerved US networks. In 2018 a source handed a BBC researcher a box of old video tapes. The format was obsolete, so a machine duplicated them. A grainy picture came into focus revealing a young woman with red hair being shown how to prime a bomb. “Your det [detonator] is the last thing to connect,” the instructor tells her. A glowing light indicates the bomb is live. “Now you know what your target is and you know what to do.” The opening sequence ends with a big explosion in a street. “We’re an audience of BBC producers, journalists and editors, and we’ve seen hundreds, maybe thousands, of hours of archive footage,” said MacIntyre. “But nothing like this.” It was especially startling to see McGuinness, then aged 21 and clearly identifiable, driving around Derry with weapons and prepping a car bomb – evidence that could have locked him up for years. With McGuinness and Bell dead, the BBC team sought others involved in the film. They found Tony Devine, who was shown accompanying McGuinness. Now a grandfather, Devine recalled the film crew’s tenacity: “They were up our ass – no matter where we went, they were there.” Des Long, who appears on screen as a gun instructor, said the film-makers had promised to shield his identity. Another instructor, Paddy Ryan, who is shown giving a bomb-making class in his Dublin home, was a member of the IRA army council. In Arizona, Jacob Stern, a retired composer, accepted Bell’s invitation to accompany the crew and score the film. Driving from Dublin airport they switched cars to evade security force surveillance. The IRA demanded – and were promised – control over the film, said Stern. “They said if any separate parts of the film were attempted to be taken to America, that we would all be shot at the airport. Just like that: ‘We’re gonna kill ya.’” There are suspicions that intelligence agencies had a hidden hand in the film. A document at Harvard revealed that Bell was a consultant for the CIA and other US agencies. That does not prove he was a spy, but his choice of director, Zwy Aldouby, raises further questions. Aldouby was a former Nazi hunter with links to Mossad, which at that time was monitoring the Libyan dictator Muammar Gaddafi, who was forging links with the IRA. There is yet another twist: Gildin, the producer, said Bell and Aldouby told him British intelligence viewed the film while it was being developed in London and before it was shipped to the US. Which raises another question: why did the spooks not pounce on material that incriminated McGuinness and other IRA commanders? No one was arrested in connection with the film. The IRA, in any case, gave advice to members who appeared on screen: if arrested, say you were acting. The Secret Army is available on BBC iPlayer and will be screened on BBC Four at 10pm on 2 April