Many of the soldiers in Matt Damon's WMD unit were actual Iraq War and Afghanistan War veterans, not actors. Damon said his biggest challenge was knowing he was an actor who was giving orders to actual soldiers.
Roy Miller is based on U.S. Army Chief Warrant Officer named Richard "Monty" Gonzales who had the real-life job of hunting for weapons of mass destruction after the fall of Baghdad. Gonzales was hired as a consultant on the film.
The traffic shots of the American convoy rolling under an overpass and encountering a traffic jam as panicked crowds flee Baghdad were shot in Spain, on a brand new highway which was not yet open to the public.
Khalid Abdalla, who plays Freddie (Matt Damon's friendly translator), played a heavy when he worked with director Paul Greengrass on United 93 (2006). However, Abdallah had to learn the Iraqi Arabic dialect for the part; he is Egyptian by birth.
The budget swelled because Matt Damon, Paul Greengrass, and the studio were unhappy with the original tame ending. The last third of the movie had to be reshot, which was complicated by the fact that Damon had already left to shoot The Informant! (2009) and the shoots had to be restaged months later to accommodate his schedule.
Igal Naor, the actor playing Gen. Al Rawi (a top commander in Saddam Hussein's army), portrayed Saddam Hussein two years earlier in the TV series House of Saddam (2008). Naor is an Israeli actor of Iraqi Jewish descent.
The gunner atop Matt Damon's Humvee is Falluja vet Marine Michael J. Dwyer, who was in a building in New York to sign up for a veteran's organization, it happened to be the same building where the casting sessions for Green Zone (2010) were taking place.
The other traffic jam, in downtown Baghdad, was modeled after a Baghdad incident captured by British cameraman Nick Turner in 2003. By coincidence, Turner was part of a CBS crew which shot some behind-the-scenes footage, and they arrived for the film shoot of that same traffic jam.
Rajiv Chandrasekaran wrote the book "Imperial Life In The Emerald City", which detailed the extraordinary levels of incompetence, ignorance and infighting that occurred within the Green Zone in Baghdad. The production team optioned the book, but this film is not an adaptation.
In the scene at the swimming pool at the Republican palace, the pool (shot in Morocco) had the deep and shallow ends reversed from the actual pool in Iraq. So the scene was shot and then the diving board was painted out and digitally replaced at the other end.