Iman Rezza has just brought out the tea and we are sitting down to drink it when volleys of gunfire split a sky thick with clouds of cordite and burning rubber. Screamed obscenities follow and armed US Marines drag five young men from a taxi and bark questions at them as they stand, their arms raised. Then the Marines lift their rifles and shoot the first man, then the next, and on until all five lie dead.

It could be just another day in the horror that is the War in Iraq. But this is peaceful Jordan, and soon the nightmare is halted by a call of: “Cut!” The dead Arabs prop themselves up in the dust and admiringly compare the fake bloodstains on their chests as the Marines pull off their helmets to wipe their sweating brows. Here, in the old Roman town of Jerash, one infamous and bloody corner of Iraq is being recreated for the cameras – not by actors, though, but by those who lived the war, Iraqis who fled the conflict and Americans who fought to quell the insurgency.

This daring project is the work of Nick Broomfield, the documentary maker best known for his quirky “Englishman abroad” persona, gliding in and out of camera shot replete with boom mike and earphones. Long before the likes of Michael Moore and Louis Theroux were stepping in front of the camera and up the noses of their inter-viewees, there was the bumbling Broomfield, trailing after such unwilling subjects as Margaret Thatcher and Eugene Terre’ Blanche, seducing the serial killer Aileen Wuornos into telling her story and enraging Courtney Love with his inquiry into the suicide of her husband, Kurt Cobain.

Broomfield’s prominence in his own films has been a constant source of irritation to his detractors, the mark of one more obsessed with self than subject. “The problem with Nick Broomfield’s documentaries is, well, Nick Broomfield,” said Jamie Gillies, of the website Apollo Movie Guide.

But after two decades of bobbing up in front of the camera, Broomfield is moving on. After the acclaim that greeted his first drama documentary, Ghosts, about the Chinese cocklepickers who drowned in Morecambe Bay, Broomfield has turned his sights on one of the most controversial, morally complex stories of our time: the War in Iraq. And, within that, one of the most fraught and complex stories of all – the killing of 24 Iraqi civilians in Haditha, already darkly referred to as the My Lai of Iraq.

Haditha was, to many in America, the moment the war was lost, after a long catalogue of disasters from the looting that broke out when Baghdad fell to the scandal at Abu Ghraib prison. The idea that America was a force for good came up starkly against reality when the first pictures and video emerged, suggesting that American troops had committed a massacre and then tried to cover up their misdeeds.

The undisputed facts of Haditha are few. What is known is that a group of Marines was patrolling the town in western Iraq early on the morning of November 19, 2005, when a roadside bomb exploded under a Humvee, killing one of its occupants. Shortly afterwards, Marines shot dead five men in a taxi and then went on to kill another 19 civilians, including seven women and three children, the youngest 3 years old.

Whether highly trained Marines lost their cool in the fury of battle and their grief at losing a comrade, or whether it happened because of the way the Marines were trained to fight, has yet to be determined. But it was the human drama that attracted Broomfield to this particular tragedy. Was it too easy to dismiss the Marines as brutal animals and Iraqis as victims? What could Haditha tell us about humanity at war?

“I thought it would be interesting to do a film about the Iraq War, but also to do something that reflects quite a complex story, where you couldn’t just choose an easy side,” Broomfield says. “And Haditha is a compelling story. There are lots and lots of Hadithas in any war. When you throw together people of different cultures, different outlooks, no language in common, these things happen.”

Having just completed Ghosts, in which he used Chinese migrants as actors, Broomfield decided to do the same with the Marines in Battle for Haditha. The dialogue was to be improvised, with no script as such, just an outline of where the story was going – which nobody in the cast would actually see. Briefly he considered using troops who were there that day, but when interviewing them for research he realised it would be impossible. “The Marines were f****d up, they were much too jittery,” he said. “Some could not keep still when we were talking to them.”

So he put word out among casting agents with links to the military community and started speaking to others not long returned from active duty.

Broomfield’s star find was Elliot Ruiz, a 22-year-old former Marine who had been, when he was 17, the youngest deployed to Iraq. Ruiz was forced to leave the Marine Corps after being seriously wounded when a car failed to stop at a checkpoint he was guarding during a mission to rescue seven American PoWs near Tikrit. His story has already been told in a Pulitzer prize-nominated play, Elliot, a Soldier’s Fugue, but this time Broomfield wanted him to tap into his experiences to tell the story of the Marines in Haditha. Ruiz, who wants to pursue a full-time dramatic career, duly obliged, but found it was not always acting. “We did this scene in the bathroom where I break down,” he tells me, standing inside the bathroom itself, built not merely as a set, but also for the Marines to use. “Nick came over and said I want you to think of something like losing a friend – and then everything I’d built up for years came out. It was a real breakdown. All the emotions came up and I couldn’t stop them.”

Broomfield later tells me the same story, seeing in it the cinema verité he is seeking to create. “He was talking about his bad dreams. Working on the film had caused him to think of them again. He started sobbing and he couldn’t stop. It was extraordinary. It makes you realise how vulnerable they are. He was just 17, a kid, to have seen what he had seen.”

As the troops get on with “executing” the taxi passengers, I visit the houses where the Abbas family – refugees from Baghdad – are living. They play civilians soon to be slaughtered by the Americans. The scene is surreal; they make me tea and we sit down to talk in their living room, soon to be trashed by US troops. Shukrieh Hameed, another member of the cast, says she had seen her own son shot dead by insurgents in front of her home in Baghdad two years earlier. The tears roll down her grief-haggard face.

An hour later I am standing with her and Broomfield on the roof of her home as she watches the Marines shoot the students. Two of them, in this recreation, are her sons. She screams as her husband runs into the room to get an AK47 to fire at the Americans, sparking the massacre. Broomfield shouts “cut” but the screams and the tears don’t stop. Afterwards I go to comfort Shukrieh. “It was like my son was killed all over again, right now,” she sobs.

“Her performance is a thousand times more convincing than most actresses,” Broomfield enthuses. What Laurence Olivier would make of this departure from “just acting” can only be imagined.

Later we discuss whether or not it should be clear to the audience that the players are not actors. Knowing what I knew about Shukrieh had become part of the frisson of watching her scene. But is it not at all exploitative to tap into the deep emotions of those who, even Broomfield admits, are intensely vulnerable? “I think people are amazing survivors,” he says. “For Elliot it’s an enormous opportunity to get out what he’s seen.”

That debate is perhaps best left to the trauma specialists. Even between sobs, Shukrieh had insisted that the pain of recall was worth it: “I have to tell people the truth about what is happening in Iraq.” Back at Casa Abbas, the family is preparing for its big scene, the storming of their house by the Marines. Iman, her husband Ghanim and their daughter Hanin, will all be “killed”, along with three Jordanian children playing other family members. Only Ayah, 12, who plays Safa, is scripted to survive.

Not having seen the script, they are unsure of what will happen. This is a deliberate move on Broomfield’s part; he wants to keep the reactions as real as possible. “I think it will be frightening,” Ayah admits shyly. “I don’t want to see my family dead, even if it isn’t real.”

Outside, another volley of gunfire splits the sky. “Yesterday we had explosions,” Ayah muses. “It reminded me of the first day of the war.”

Highlights from the Broomfield CV

Heidi Fleiss: Hollywood Madam (1995) Heading to the States, the maverick film-maker tracked down the infamous brothel owner. Unintentionally hilarious and at times moving, the film helped to establish the director’s trademark low-key delivery.

Kurt & Courtney (1998) As an introduction to the music of Kurt Cobain and Nirvana, Broomfield’s study falls flat. Instead, he provides a brilliant portrait of the late singer’s fiery relationship with his wife Courtney Love.

Biggie and Tupac (2002) Another stab at the music industry, this time the violent world of gangsta rap. Broomfield is deliberately out of his depth here – and what we get is a great rap parody.

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