Chief Warrant Officer Roy Miller (Matt Damon) © Universal

Matt Damon and director Paul Greengrass, who collaborated on The Bourne Supremacy and The Bourne Ultimatum together, are now turning their creative attention to the early, chaotic days of the Iraqi War with their new action-thriller Green Zone.

Inspired by the book Imperial Life in the Emerald City, the movie spotlights Chief Warrant Officer Roy Miller (Damon) and his team of Army inspectors who are dispatched to find weapons of mass destruction that they believe are stockpiled in the Iraqi desert. Going from one booby-trapped and treacherous site to the next, Miller stumbles on an elaborate cover-up that is set in motion to overturn the purpose of his mission.

Matt Damon spoke of his new movie and his relationship with director Paul Greengrass at the press day for the film in New York.

This is the third time you’ve worked with Paul.

Chief Warrant Officer Roy Miller (Matt Damon) and director/producer Paul Greengrass on the set © Universal

I love working with Paul and I just love doing big movies with him and the whole kind of action-thriller genre.  I just think he does it so well. In this case the question I think was could we take a movie that’s a big action thriller and set it in what we all recognize as the real world, but still make it an entertaining, fun, Friday night at the movies that I think people kind of expect from Paul.

So he did a lot of things I thought were great, instead of hiring actors to be in the unit I’m leading, he hired all vets from Iraq and Afghanistan. These guys had just come back from duty and joined the cast, and it was really amazing to have 30 guys, because when we’d do a scene where we’d hit a house, with these guys you didn’t have to explain to them what to do, they would just do it for us and someone would stand in for me.

Chief Warrant Officer Roy Miller (Matt Damon) © Universal

They’d do it fast, and then they’d walk it slow, and I’d just kind of be absorbed in the group and they’d show me what to do and we’d all do it together. So it was really great in terms of feeling like you’re authentically playing a role or that the movie is grounded in authenticity.

Tell us a little about your character of Warrant Officer Roy Miller.

Like any action thriller you’ve got to have a protagonist that has basically a noble quest that he’s on for the truth, and in this case we actually had in 2003 what were called MET teams, Mobile Exploitation Teams, and they were comprised of guys drawn from the artillery division who worked security, and then scientists and explosives’ experts, and these guys went into these sites where we had intelligence that there was WMD, they would if necessary fight their way into these sites because they were in a mad dash to find these things before they could ever be used.

And so Roy Miller is based on a real guy, who’s leading one of these teams who goes in with the expectation obviously that he’s going to find the weapons at some of these sites and then realizes pretty quickly that there’s a disconnect between what he’s got in his Intel packet and what he’s actually seeing on the ground. So he asks the logical next question, which is, ‘What is going on?’ and he becomes kind of obsessed to find the truth about what’s going on.

Defense intelligence agent Clark Poundstone (Greg Kinnear) confronts Chief Warrant Officer Roy Miller (Matt Damon) © Universal

You’ve got a wonderful cast in this.

The cast is great, just leaving myself out of it so I can speak freely and immodestly about my cast mates, they’re incredible. I always know if I’m acting opposite someone great, I never have to do anything, I never have to think about it, it’s so easy, and it felt that way for this whole movie.

Every scene I had was with a world class actor from Greg Kinnear and Brendan Gleeson, and if people saw United 93, they’ll know who Khalid Abdalla is, he’s a great young actor. Every day if I wasn’t working against one of these great world class actors it was an actual veteran from Iraq or Afghanistan. They were totally believable, and it made my job really easy, I was privileged to be a part of this group.

Briggs (Jason Isaacs) and Chief Warrant Officer Roy Miller (Matt Damon) © Universal

Were the scenes ever improvised?

We did a lot of improvisation. Paul likes to have a very free atmosphere on the set. And for certain things like hitting a house, and going in and interrogating somebody, knowing there was a high value target who just escaped out the back door, we’d have things that we knew we had to say, but Paul is always looking for those happy coincidences that happen when you get people not quite knowing what’s going to happen next. And then it’s a process of editing, where he goes and re-imposes a structure on scenes again and returns back to the screenplay.

It’s a really fascinating process that is great as an actor, because there’s an element of danger to it, you don’t really know what’s going to happen next and that means you can’t plan out or over-think a scene and say, ‘This is where I’m going to give my steely gaze,’ because you don’t know what’s coming next and you don’t know what the actor opposite you is going to do, so it keeps you very locked into what you’re trying to do in the scene and what your agenda is and what’s getting in the way of that.

Judy Sloane

Judy is Film Review Online's regular Los Angeles based reporter. More by Judy Sloane