Matt Damon with long-time friend, director Paul Greengrass, on the set of 'Green Zone.'

The year was 2003.

The mission: find the hidden weapons believed to be stockpiled in the Iraqi desert.

The players: U.S. Army Chief Warrant Officer Roy Miller and his team of inspectors.

What they found instead: An elaborate cover-up that threatens to subvert their mission.

War makes heroes and villains of us all—it really just depends on which side you stand. In this case, these soldiers chose to side with the truth as they discovered it. 

When director/producer Paul Greengrass (“The Bourne Supremacy,” “The Bourne Ultimatum,” “United 93”) began his journey to make the movie “Green Zone,” he knew one thing—he wanted something that would grab the world by its balls. But he also wanted it to be wrapped in the authentic details of a war zone.

“This is not a movie about the war in Iraq,” Greengrass emphasizes. “It’s a thriller set in Iraq, and that’s a very different proposition. In my experience, thrillers are at their best when they’re in extreme environments where the moral challenges are acute.”

The last two Bourne films he helmed achieved a rare feat: the ability to impress critics and worldwide audiences alike. And in the thick of that success is his actor of choice, Matt Damon.

Of Damon’s performance in “Green Zone,” Greengrass notes, “This is the kind of role people want to see him in. He’s one of the world’s great physical actors. He commands attention because you know he’s going to go to exciting places—to be absolutely determined to get to the truth and exhibit courage. He’s going to be running and jumping and chasing and fighting and doing all those things that you want to see Matt Damon do. But he does them with class and integrity, and also tells a great story.”

Damon’s character, Chief Warrant Officer Roy Miller, is based on a real person: Monty Gonzales, who led the Mobile Exploitation Team Alpha (MET A) into the first weapons of mass destruction (WMD) site for exploration. Described by Damon as “a good soldier and a decent man,” Damon related, “He fully expected to find these weapons and told me he wanted to be the first one on CNN holding the evidence.”

But in the course of fulfilling his mission, Gonzales realized something was wrong. “He realized it in the first site he explored—a porcelain factory that was supposed to be a duel-used facility that also harbored weapons of mass destruction.”

Whereas in the movie, the soldiers didn’t suspect anything was amiss until after the fourth time they had gone out to explore a WMD site, Damon revealed, “Monty actually realized something was wrong on his very first attempt to find WMDs, and then all the team leaders started calling each other.”

On the flipside of playing a role, Damon’s experiences on set had truly become invaluable to him. Meeting Gonzales for the first time, Damon spent about four or five hours talking with the war vet. “He's my age and we graduated from high school the same year, though we chose very different paths.”

Whereas Gonzales had chosen to serve the country by joining the military, their paths crossed because of this movie—which prompted Damon to ask Gonzales why he had decided to participate in its making. “He thought about it for a second and said something that I think came at a price for him: ‘Because we need to regain our moral authority,’” Damon related.

Damon likewise admitted to benefitting from Greengrass choosing to cast real veterans in the movie. “It felt like I had 30 technical advisors there with me. Everything they do is correct and you don’t need to tell them how to stand or where to go. If you took a group of actors and tried to make this film, it would require a lot more energy and work, and even after sending us all to boot camp, you still wouldn’t achieve that sense of authenticity.”

Damon knew that Greengrass had always wanted to make films about two of the most cataclysmic events that happened in just the last decade—9/11 and the war in Iraq. The director had already delved into the heroism of the common citizen in “United 93;” by the time he and Damon were working on “The Bourne Ultimatum,” Greengrass told his actor that he was ready to make a movie about Iraq.

Only, Damon revealed, “He couldn’t quite figure out what it was going to be until he came across Rajiv Chandrasekaran’s book ‘Imperial Life in the Emerald City.’ I remember we were in Tangiers when he told me: ‘You have to read this!’”

And now, moviegoers will get to see the gritty reality of this war through “Green Zone.” Shot mainly in Morocco and partly in Spain (“Believe me, the South of Spain doesn’t look anything like Baghdad, but Paul’s vision and Peter’s expertise made it happen,” enthused the lead star), Damon is thrilled that the movie will finally come out—it opens in local theaters on March 12.

“Now, I’m curious to see how people will react to it,” said the versatile actor, whose recent on-screen success was via director Clint Eastwood’s “Invictus.”