Read more about the director of In the Loop, Armando Iannucci, and his influence on Sacha Baron Cohen, Ricky Gervais and Stephen Colbert.

In the Loop is the feature-film debut of Armando Iannucci, who created the BBC comedy series The Thick of It, about the unseen workings of the British government. Some of the characters from that show reappear here, most notably Malcolm Tucker (Peter Capaldi), a ferociously ambitious and epically profane Scotsman who's the director of communications for the never-seen prime minister. In the film's opening scene, Simon Foster (Tom Hollander), the dim-bulb minister for international development, ends a routine radio interview with the cryptic observation that "war is unforeseeable."

When reporters press him to elaborate the next day, Simon continues to heap up nonsensical equivocations: "To walk the road of peace, sometimes you have to climb the mountain of conflict." Simon's convenient vagueness makes him a pawn for both the hawks and the doves at the U.S. State Department, where consensus is building for a war in "the Middle East." (Like Tony Blair and George Bush, Iraq is never mentioned by name, nor do we learn anything about the rationale for war.)

Simon and his recently hired young aide, Tobey (Chris Addison from The Daily Show), travel to Washington, D.C., to attend a meeting of the top-secret "Future Planning Committee," the euphemism for a pro-war committee created by Linton Barwick (David Rasche), a Rumsfeldian bigwig at the State Department. Though Simon's been advised that he's only "meat in the room," sent to rubber-stamp the committee's rush toward war, he keeps opening his mouth and cramming his foot in it. Meanwhile, diplomat Karen Clarke (Mimi Kennedy) is trying to claim the British envoy for her own anti-war camp, aided by a pacifist general (James Gandolfini) and trailed at all times by her ambitious aide Liza (Anna Chlumsky), who's an old college chum of Tobey's.

That's a lot of story to keep track of, and I didn't even mention the delectable minor players, including a litigious rube played by Steve Coogan and an icily competent PR liaison played by Gina McKee. Filmed with a mobile handheld camera and packed with overlapping, partly improvised dialogue, In the Loop feels like an on-the-fly news documentary set in a preposterous yet plausible alternate world. It's The War Room (the 1993 documentary about Bill Clinton's upstart campaign strategists), but shot in the war room of Dr. Strangelove.

Peter Capaldi's performance as Malcolm is the jewel in this movie's comic crown. You haven't been sworn at till you've been sworn at by Malcolm Tucker: When he's not calling his colleagues "vinegar-faced manipulative conebags," he's threatening to drown them in tanks of sewage or ram them with a lubricated horse cock. Capaldi packs so much coiled rage into his slight, loose-limbed frame that after a few scenes, you begin to laugh the moment he appears onscreen.

But In the Loop is a true ensemble comedy; the actors riff off each other with an understated deadpan familiar from the original British Office (whose influence also shows up in the bleakly realistic production design, all gray carpets and cluttered, windowless rooms). Tom Hollander brings a Chauncy Gardner-like blankness to the bumbling Simon. Mimi Kennedy, as the calculating but not completely unprincipled Karen Clarke, gives a dryly funny, emotionally nuanced performance that at times channels Catherine O'Hara.

There are moments when the script, which was co-written by Iannucci and three BBC colleagues, staggers under the weight of its own verbal felicities. Amid the dense volley of rococo insults and diplomatic doublespeak, the occasional line of dialogue will emerge that sounds overwritten and arch. But for every joke that never quite leaves the page, there are 10 that seem to emerge sua sponte from the mouths of the performers. Britain's diplomatic corps may be as clueless and impotent as In the Loop suggests, but British comedians are fully capable of taking over the world.