Kristen Stewart Becomes a Soldier, Trains With Marines

Twilight star plays a guard at Guantanamo Bay in new movie

Playing a soldier is a lot more than just slipping into some fatigues and slinging a gun over your shoulder.

Just ask Kristen Stewart.

In Camp X-Ray, the Twilight star plays an army guard at Guantanamo Bay who befriends a prisoner (Peyman Moaadi) who's been there for eight years. Directed by Peter Sattler, the film also stars Lane Garrison as a fellow soldier.

"I spent a few days with a couple of Marines that really put me through the ringer," KStew told me yesterday at the Sundance Film Festival premiere of Camp X-Ray. "It was awesome. They're great guys.

"We wanted to represent them in the best possible way we can and if I was remotely unauthentic, I would die," she added. "I would hate that. We did everything we could to keep it real."

But you won't see Stewart in combat. "I had to move and respond like a soldier that was not given any room to breath," said Stewart, who was wearing her character's dog tags at the premiere. "She's not using all the things she's been trained to do. She's walking around in circles. I needed to look like I learned those things but couldn't really display any of it."

As we first told you yesterday, Stewart would unwind from filming by hitting some golf balls.

"We built a driving range in the prison and I brought like 400 golf balls," Garrison said. "We would go out there and hit about 100 golf balls. She has an amazing swing."

Check out more of my chat with Kristen in the video below. Plus, see her show off her saluting skills.