How inevitable that a maddeningly intractable war should get its most confrontational fictional treatment from a filmmaker who is alternately relished or hated. Brian De Palma, a veteran of conflicted voyeurism in films such as “Dressed to Kill” and “Femme Fatale,” has long been unfairly dismissed according to the hoary dichotomy of style and substance. For months already (the film made its American premiere at the New York Film Festival), critics have fulminated against his latest, the outraged and outrageous “Redacted,” an agitprop bombardment loosely based on the March 2006 rape and murder of Iraqi civilians by American soldiers in Mahmudiyah, Iraq.

A simulated multimedia mishmash of video diaries, a portentous French documentary, Islamist Web sites, and more, “Redacted,” with its calculated lo-fi barrage, suggests Mr. De Palma has recently curled up with You-Tube, Jonathan Caouette’s “Tarnation,” and pungent Lars von Trier material. The plot, reminiscent of Mr. De Palma’s own “Casualties of War,” pits degenerate grunts against conscience-stricken comrades and settles into a chronicle of the lead-up to the crime, its nightmarish execution, and the aftermath.

Our primary visual conduit in “Redacted” is the handheld desert-camp footage that Private Angel “Sally” Salazar (Izzy Diaz) is shooting in a bid for film school. His troopmates, Rush (Daniel Stewart Sherman) and the emptyeyed Reno (Patrick Carroll), are the crass good ol’ boys who announce their brutal intentions over a game of poker. Bespectacled Blix (Kel O’Neill), who’s introduced reading John O’Hara’s “Appointment in Samarra,” is the intimidated liberal voice of decency. Slowly devastated by it all is Lawyer McCoy (Rob Devaney), a family man (and son of a former officer), who by the end resembles a burnt-out soul from the documentary “The War Tapes.”

After some deft switch-ups, Mr. De Palma’s film becomes purposefully amateurish and melodramatic in a way that’s more than straightforward buttonpushing, but still needlessly undisciplined. He seems destined to irk even those who would sympathize with his evident disgust, thanks to his story’s parodic “bad apples,” faceless immoral officers, illogical camera coincidences — not to mention his wildly uneven direction of actors. It’s a shame that an important attempt at reactivating a numbed audience’s shock should also aggravate for the wrong reasons.

“Redacted” does try to evoke the enervating, fragmented mediascape that is the public’s experience of war. Mr. De Palma weaves into the flow an Islamist Web site that posts videos before and after a bombing, and later we hear from a “loony left” YouTube screed and a teary-eyed Web log titled “Just a Soldier’s Wife” (Lawyer McCoy’s, to be precise). Next to Salazar’s handheld rambles, the partly static Web sites, which are blown up to movie-screen size, produce the familiar jolt of events and commentary placed on the same platform. And with an intermittent parody of a stately investigative French documentary, Mr. De Palma shows the alternative to being a fly on the wall.

Mr. De Palma opens “Redacted” with the proviso that it “visually documents imagined events,” a bit of language as twisty as reports on the war’s progress. The film finishes with a “Dogville”- like litany of actual images of brutalized Iraqis, concluding with a restaged photo of the young Mahmudiyah victim. Magnolia Pictures, no doubt lawsuit-shy, has “redacted” the identities in these photos, but what’s striking is how much more disturbing they then become — howling abstract holes where the center of their faces should be. It’s a fitting irony for a movie that, wittingly and unwittingly in all its faults, can still strike a nerve.