“Fury” is a movie about war, but Jimmy Kimmel was stunned to learn that there was fighting going on during the shooting of the film even when the cameras weren’t rolling. Jon Bernthal, who stars in the David Ayer-directed WWII tank film, casually mentioned the film’s early morning fight club.

“David, in all his films, feels strongly that everybody fights each other every single morning before we go into our tank training and our rehearsals,” he said, at which point Kimmel had to stop him for clarification.

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Bernthal explained that everybody gets involved first thing in the morning. They’re only given MMA gloves and they have five minutes per round. It’s supposed to be a way to build camaraderie and a sense of equality.

But he did notice one thing. “We were definitely sort of told not to hit each other in the face,” Bernthal said. But on his first day of sparring, he found himself squaring off against Ayer himself.

“I’m sort of like, alright dude, I’m kind of gonna let you dictate this thing,” he said “And I’m standing there and he just — Wapow! — He just hits me right in the nose, you know. Blood starts coming out. I’m like alright, it’s gonna be this kind of party.”

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He said that when Brad Pitt showed up on set, they were told even more implicitly to not hit in the face. “I felt like there was a direct correlation to how important you were in Hollywood, or how important you were to that movie, to whether or not you could actually get hit in the face,” he said.

Kimmel called it insanity, but Bernthal disagreed. “I feel like it was awesome. It was a great way for us to get to know each other,” he said. “I felt it really bonded us. I’m gonna suggest it on the next rom-com I make.”

Fan can see if that bond translated to the screen when the film is released. “Fury,” written and directed by Ayer, also stars Shia LaBeouf, Logan Lerman, Michael Pena, Jason Isaacs and Scott Eastwood. Columbia Pictures will release it to theaters on Friday, Oct. 17.