On the morning of November 19, 2005, a hidden roadside bomb exploded under a US marine Hum-vee on patrol in a street in Iraq, ripping in half the body of the driver Lance-Corporal Miguel “TJ” Terrazas, a decorated war hero. His legs remained in the vehicle under the steering wheel. His upper body was thrown out into the road.

In the following hours the men of Kilo Company, 3rd Battalion, 1st Marine Regiment, killed 24 unarmed Iraqi civilians. The dead included babies, women and children and a man in a wheelchair – all shot at close range as marines swept through the houses near the deadly explosion. A marine urinated on one of the bodies.

In the houses, it is said, they chased each other around the rooms with body parts. Safa, 12 at the time, lost her mother and father, four sisters, aged from three to 14, her brother, aged eight, and her aunt.

However, after the deadly mopping-up operation was over, the marines put out a false story that the killings had been the result of roadside bombs. An investigation, later picked up by Time magazine, revealed the massacre. It suggested that the marines had rampaged through the area to avenge the death of 20-year-old “TJ”, a popular marine.

The incident occurred at Haditha, a small and dusty town on the banks of the Euphrates River west of Baghdad which was then the centre of the Sunni insurgency. But until the story broke, not a single marine commander had considered the possibility that the killing was a war crime. When it did finally emerge, the incident shocked America and, in Iraq, it was a huge setback for the battle for hearts and minds.

Haditha became a metaphor for the war just as the My Lai massacre had been for Vietnam. Next month two marines will finally stand trial in connection with the killings. Two others will be tried later this year. But most of the marines charged with murder have had their cases dropped.

Next month will also see the release of a powerful film called Battle for Haditha by Nick Broomfield, the director of hard-hitting docudramas such as Ghosts, about the Chinese immigrants who drowned while collecting cockles at Morecambe Bay.

In his film, due out on February 1, Broomfield uses ex-marines who served in Iraq to play the parts of the marines of Kilo Company, and Iraqi civilians, some of them from Haditha itself. It captures every unnerving second of the killings. Although it was made according to a detailed structure, most of the dialogue was improvised.

Broomfield thinks the reason the film is so powerful is because it brought back so many memories among the ex-marines and Iraqis reenacting the massacre. One woman who was leading the grieving of the survivors had herself lost members of her family. While preparing the film Broomfield had been able to meet and interview for many hours some of the marines who had taken part in the actual incident at Haditha.

Broomfield said last week he had always wanted to make a “generic film about the language of war”. But he focused on Haditha because the trial and publicity meant it was easier for the audience to relate to. He believes, passionately, that what happened on that November day was inevitable and that the trial of the marines will be a charade.

“They have already let half the guys off,” he said. “They have discredited all the Iraqi witnesses as being prejudiced. They have discredited the two marines who came up with evidence implicating the others. They have done all they can to negate anything that pushes it towards murder.”

Broomfield is right that the killing of innocents at Haditha was not exceptional. It grew out of the horror of the Iraq war. Some of the marines of Kilo Company were on their third combat tour. They had come from the battle of Falluja, the most intense combat the Americans had been involved in, where they had seen their buddies die and had indiscriminately killed many Iraqis.

From the conversations he has had, Broomfield thinks that by the time Kilo Company got to Haditha they had seen so much carnage that killing did not mean much to them any more: “On that day they were chasing each other round with body parts and they thought it was very funny. It was their way of surviving it.” The hard truth is that the US marines are good at killing and rejoice in it. Their training instils a terrible indifference to killing. Their whole spirit reinforces each other’s willingness to kill. They boast about their kills and if you have not killed you are not held in high regard. To those who have never been in combat this may seem disgusting. But as a young reporter in Vietnam I learnt that the more soldiers see of death the more it becomes normal.

Everything I have seen in war – from Vietnam to Iraq over 30 years – reinforces that view. There are always soldiers who exult in the kill. I saw it myself all too frequently in Vietnam, where American troops revelled in posing for photographs with their buddies among heaps of mutilated corpses of Vietcong and cut off their enemies’ ears as souvenirs. There is, as soldier friends admit, something heady and powerful about the proximity of death and the power to kill and be killed. And it takes a singularly strong-minded soldier to be able to hang on to acceptable standards of behaviour in the horror.

Broomfield believes that the young marines were, in their own way, victims of the war, just as the insurgents and ordinary Iraqis were. They had all been thrown together in the most terrible of situations, struggling to stay alive. “I think the trigger pullers are victims, trying to stay afloat, trying to stay alive until the end of the day,” said Broomfield.

“The idea of the film was to get into the heads of the main participants of that day and view it from their point of view, as sympathetically as possible for each group, and dispel the idea of rights and wrongs and goodies and baddies which is how war is normally presented. Probably, and more accurately, they are all victims except for the grand architects of the whole thing.” He was clear who they were – George Bush, Dick Cheney, Donald Rumsfeld – who gave the message that human rights abuses in the “war on terror” were acceptable.

Inevitably Haditha has been compared to the My Lai massacre when Vietnamese villagers were herded into a ditch and shot by the troops of Charlie Company under Lieutenant Rusty Calley. More than 500 civilians were killed. Girls were raped, babies were ripped from the wombs of pregnant women and old men were thrown down a well. The slaughter was finally stopped by a US army helicopter pilot who landed his aircraft between the GIs and the villagers and threatened to shoot the Americans if they did not stop.

A whole generation of American officers grew up being taught the lessons of My Lai. But in Vietnam, My Lai was by no means the worst of it. In the past few years, veterans of the Tiger Force of the 101st Airborne have finally revealed how they ran wild in Vietnam killing anyone and everyone they came across without regard to age, gender or innocence.

The fact is that war, whether it is Iraq or Vietnam, empowers soldiers to kill without moral or legal sanctions for reasons of national purpose. The slaughter of civilians, accidental or deliberate, always happens.

The cruel irony is that the insurgents who planted the bomb that killed “TJ” and led to the deaths of 24 innocent Iraqis are now allies of the American marines who are paying them money to fight Al-Qaeda.

Despite all the hatred generated by incidents such as Haditha, yesterday’s enemies are today’s friends. The real aberration is war, not the men who fight it.

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