He has been Hollywood’s roadside bomb for 40 years. You cannot pass a Brian De Palma film without expecting it to explode. It might be the popcorn detonations of Carrie and Dressed to Kill, showering feel-good frissons over connoisseurs of surreal horror. Or it might be the shrapnel storm, dividing critics and threatening to decimate a fan-base, of his controversial new movie about the Iraq war, Redacted.

Opening in Britain next week, the Venice Silver Lion-winning film is already, for some, the last word on the ground-level realities of this conflict. It takes its title from the censoring impulses of the US media, conducting what De Palma sees as a mission to disinform, while its style comes from the vivid, retaliatory freedoms of the internet. Re-enacting a true incident, the rape and murder of a teenage Iraqi girl by American soldiers, Redacted combines IT-era audiovisual techniques with the unpredictability of the era of the improvised explosive device.

De Palma, now 67, looks like a combination of doomwatching prophet and weather-grained rebel. The dark-socketed eyes peer from a face with a smoke-white beard. The voice is a rasp that doesn’t suffer fools, gladly or at all. He exudes the ferocity of a survivor, having come back from failures (Femme Fatale) and fiascos (The Bonfire of the Vanities): that which has not killed him has made him strong.

Redacted throws a cast of unknowns into a style-blend of video diaries, weblogs, CCTV footage, newscasts, interrogation tapes. For a director previously known for his darkly voluptuous riffs on classic Hollywood cinema, coaxing fresh patterns from old fabrics, this seems a whole new game plan.

“Actually, it’s like the home-video style I used long ago in a film called Hi Mom! (a low-budget 1969 film about a guerrilla black theatre group). Almost every technique in Redacted came from sources I found on the internet. I thought it was the best way to present the story, although since I was dealing with an actual incident, for which real soldiers were being prosecuted, everything had to be vetted by lawyers. Since I couldn’t use the actual language or details, I mainly followed the characters and story structure of Casualties of War.” That was De Palma’s powerful Vietnam war movie, starring Sean Penn, about a rape and murder by US soldiers.

“I wanted to show that the Iraq and Vietnam wars are very similar. Both films explore what happens when you put young American boys in a situation where they don’t know why they’re there, they don’t speak the language, and they can’t tell the insurgents from the civilians. Their only bond is their loyalty to each other and, suddenly, one of them is assassinated, as in Casualties, or steps on an IED in Redacted. They then turn all their anger on the populace, who they think are complicit in the crime.”

To the charge levelled by some that Redacted is “war porn”, pruriently showcasing brutality and atrocity, De Palma responds: “That’s absurd. The internet is filled with images far worse than mine. It’s just that in the US we have to search for them, because they’re censored from the mainstream media. My attitude is, if you invade a country and occupy it, killing over 100,000 civilians, you should have to face the picture of what you are doing.”

None of De Palma’s earlier work, not even Casualties of War, could have prepared us for the new film’s gut-led extemporaneity of style. Yet it takes only a small amount of hindsight to discern the current running between these contrasting virtuosities, between “then” and “now”.

Dressed to Kill, Blow Out and The Untouchables were brilliant essays in aesthetic bravura, working viscerally and not just visually. If there are elements of mimicry, then so there are in The Goldberg Variations or Goya’s “Naked Maja”. If De Palma seems as fascinated by shape as by substance, so were Schoenberg or Jackson Pollock.

“I’m an abstract expressionist,” the director said 15 years ago, when I interviewed him about his thriller-psychodrama Raising Cain. “I play with the form, but the form is as important as the content. Ninety-nine per cent of movies don’t deal with the form, they just photograph people talking to each other, or driving up to buildings, or walking down a street. They photograph the script and don’t use the elements of form and structure at all.”

To accusations of gratuitous violence he replied. “I deal with things in the frame and violence is an exciting part of the form. Violent action is like a crescendo in music. It makes people jump, it’s very disturbing. Do composers get these questions? Violent music is an aspect of the form. To take a moral stance is completely irrelevant.”

De Palma’s background, though, almost invites these judgments about scientism shading into sado-voyeurism in his cinema. As a boy, he watched his surgeon father perform operations. (And, for the record or for those seeking evidence of spooky precocity, he once won second prize in a National Science Fair for a project on The Application of Cybernetics to the Solution of Differential Equations.)

Sensitive to notions that he is a cold-fish form fetishist, De Palma bridles, too, at the repeated charge of indebtedness to Alfred Hitchcock. “It’s a trite perception. Hitchcock was interested in visual storytelling, so am I. He had a strong movie eye, so do I. He knew that cinema was a pictorial medium, a great white canvas, and that you don’t just fill it with words.”

Even so, Redacted seems like the beginning of a new De Palma period, if not of a new De Palma. I mention the astonishment felt by Venice festival-goers when they saw The Black Dahlia one year – which seemed the exhausted last gasp of De Palma’s exploration of the classic Hollywood thriller – and Redacted the next, which might have come from a different director or one unrecognisably rejuvenated.

“What amazed me in many of the reviews,” he says, “was that they completely misunderstood the form of Redacted . If it doesn’t fit into a genre they’re familiar with, they reject it out of hand as ‘amateurish’ or ‘slipshod’. They bring all kinds of critical preconceptions that completely miss the point.”

No, no, I protest (thinking De Palma has missed the point himself). I mean, people thought this was a good departure. Instead of De Palma movies in which the aesthetic determines or directs the content, here was one in which the content – the human content – seems to have burst through the form. But an unrecanting formalist won’t have even this. “What fascinated me was that here was a new set of styles that provided a new way of telling a story I’d told before [in Casualties of War]. I also tried to make you aware, as a viewer, that the images you’re seeing and the way they’re constructed can be presented to create any point of view. You think this is real because of the form it’s in, and of course it’s all fictionalised. So maybe you should think twice when watching a report by an embedded journalist who’s running around convincing you everything is real, authentic and spontaneous.”

Touché. Whichever way you come at it, Redacted isn’t simple viewing. Its adoption of off-the-cyberwall styles rewrites the mainstream American docudrama. Is it going to rewrite De Palma’s own movie-making? “I’m fascinated by the possibilities. The internet changes all the time. The younger generation watches movies there now. I noticed my own Body Double showing the other day; they had posted the whole film. My daughters watch most things on computer: DVDs, YouTube. They’re not sitting in quiet theatres watching a large screen – they do that, too, but they spend a lot more time surfing the net. This is the way young people are watching the narratives of our culture. Cinema has to take notice and respond.”

‘Redacted’ opens in the UK on March 14