Aaron Eckhart has admitted to being "horrible" on the Battle: Los Angeles set.
The actor played fierce and tough-talking Marine Staff Sergeant Michael Nantz in Jonathan Liebesman's blockbuster, which also stars Michelle Rodriguez and Ne-Yo, and continued to be him, even when the cameras were turned off.
"I was horrible - I was in character all the time and I pushed the cast because I wanted this movie to be real," he said.
"Sometimes I got mad at them and sometimes they didn't like me - that was hard. It can be a lonely feeling but you've got to do it for the sake of the film - and I think when they see it now, they appreciate it."
The 42-year-old wanted to possess the character completely, for the sake of 'reality'.
Aaron added: "For me it's always about the acting and I took that very seriously. I wanted the audience not only to have fun, but also to feel. The actors have a responsibility to give everything we possibly can, to be as real as possible, or else we've short-changed them."
And that is irrespective of whether the film is an independent art-house or a mammoth popcorn movie.
"I like any genre of film as long as it's based in reality and the actors believe what's happening is real. If they don't believe it, I won't believe it - and that was important to me in Battle: Los Angeles," he said.
:: Battle: Los Angeles is in cinemas now.