The Oscar nominated British director Paul Greengrass seems drawn to "issue" movies. His feature directorial debut was the disease-of-the-week movie The Theory of Flight (1998), and he found acclaim with the explosive Bloody Sunday (2002) and the gripping, grueling United 93 (2006), though none of those exactly resulted in a bonanza of ticket sales. He seemed to come closer to his true calling with the second two Bourne films, The Bourne Supremacy (2004) and The Bourne Ultimatum (2007), bringing his gift for tense action as well as uncommon intelligence to a pair of summer action films. If there were any "issues" in those movies, they were buried deep in the kinetic plots.

Now we find Greengrass at a crossroads. Clearly the issue movies bring more glory and more personal satisfaction, but the action movies bring in happier customers and more riches. It's a conundrum many artists have faced since the days of Sullivan's Travels (1941), when a comedy filmmaker hit the road to make a film about the "real America." But Greengrass has asked an interesting question: why not do both at once? The answer to that question is Green Zone. Loosely based on a nonfiction book by Rajiv Chandrasekaran, it's a fictionalized thriller with fictionalized characters, taking place in a realistic setting. (Greengrass credits the 2006 book with helping him jump-start a project he had begun working on in 2004.)

On the downside, Green Zone turns out to be a rather routine thriller. But on the upside, it's more fun than most other Iraq war movies, and there are no soapbox speeches or finger-wagging; it leaves behind the stern importance usually associated with this genre. This movie will probably attract a bigger audience than any other Iraq War movie, and the shady, sinister origins of the real-life war may finally come clear to many people. If Green Zone had been released just a few years ago, during the Bush Administration, people like Ann Coulter and Rush Limbaugh would have risen up roaring, accusing everyone involved of being traitors.

Matt Damon is one big reason the movie works at all, even though his character, Chief Warrant Officer Roy Miller, is a good deal less interesting than Jason Bourne. He's a straight-thinker, and barges into each situation convinced that "doing the right thing" will be enough to get him out again. Miller's job is to find WMD (the infamous acronym for "Weapons of Mass Destruction"). Each day he follows detailed sets of instructions, and ventures into dangerous parts of Baghdad, only to find empty buildings. A good soldier should merely do his duty, but Miller can't help asking: where is this intel coming from? Who thought there might be WMD in an abandoned toilet factory?

His asking immediately makes him an important enemy: Pentagon Special Intelligence man Clark Poundstone (Greg Kinnear). Poundstone's job is to keep the origins of the Iraq War alive at any costs. In his book, the WMD exist and we will find them. But CIA Baghdad bureau chief Martin Brown (Brendan Gleeson) understands what's really going on, and knows that the simplistic "we won and they lost" being sold on the TV news is frankly not true. Brown slips Miller his card and hints that something must be done.

Another interesting, if underdeveloped character is Lawrie Dayne (Amy Ryan), a reporter for the Wall Street Journal, who is largely responsible for printing the myth about the WMD and helping keep it alive; Dayne is shown as just a bit naïve, standing up and applauding during Bush's notorious "Mission Accomplished" speech of May 1, 2003, and unable to grasp that such high ranking government men would lie to her.

While out on a patrol, an Iraqi citizen -- who calls himself "Freddie" (Khalid Abdalla) -- approaches Miller. He wants to help and knows where a meeting with some high-ranking Iraqi officials is being held. Miller investigates and catches a glimpse of General Al Rawi (Igal Naor), who is considered one of the top Iraqi villains (he's the Jack of Clubs in the infamous "most wanted" deck of cards). After some chasing and shooting, the general gets away, but Miller comes up with a little black book containing the locations of the general's safe houses. Miller delivers the book to Brown, but Poundstone takes an extreme and urgent interest in the book as well.

This leads us to the movie's centerpiece scene, and the one that sets it apart as a war movie. Inside the "Green Zone" of the title, where all the suits work, a privileged few are seen lounging around a huge swimming pool (just a few scenes earlier, Iraqi citizens take to the streets to protest their lack of drinking water). Bikini-clad bathing beauties are wandering around, and they even have beer and Domino's pizza! It's huge shock, accompanied by the realization that it's so astonishing that it must be true. It's the visual equivalent of the hypocrisy behind the entire war.

Of course, the general is the key to the entire plot, and Miller hopes to bring him in and spread the truth about the WMD to the world. ("This is the reason we went to war," he exclaims.) But like Tom Cruise's plot to kill Hitler in Valkyrie (2008), history already shows that this plan did not work out too well. It's partly because of this factor that the movie grows increasingly unsatisfying as it goes. (Last year's The Men Who Stare at Goats added a very satisfying, ironic twist to its similar ending that Green Zone can't match.) It's possible to suspend disbelief to accept "Freddie" approaching the Americans and offering his help. It's asking a bit more to accept the existence of a plot device like the "black book," but it's asking a bit too much to accept that Miller would go storming around, disobeying orders at every turn, and escape without a lick of punishment.

Then we have Greengrass' trademark shaky-cam style, which worked brilliantly in all four of his previous films. He is one of the few filmmakers that understands the concept of establishing space and distance and relationships between characters; once those things are accomplished, then a filmmaker can shake all he wants without losing the audience in a sea of confusing chaos. But here Greengrass appears a bit confused himself, especially toward the end. There's a climactic chase scene that takes place among several players, running through alleyways in the dark, and it's difficult, if not impossible, to determine what's going on for several long minutes.

But even if it doesn't work all the way through as a thriller, it at least works part way as a war movie, and the "issue" part of the movie does work. Even if Green Zone not as brilliantly constructed as The Hurt Locker, Greengrass and screenwriter Brian Helgeland have found a way to foreground the Damon character and background the politics. They have also painted the politics in very simplistic, but realistic strokes. The result is that, rather than being told what's at stake, large audiences will be able to read the politics at their own speed and draw their own conclusions on their own time.