Brad Pitt has said he feels comfortable with his 13-year old son Maddox seeing his harrowing Second World War film Fury.

The father of six feels his oldest son can handle the graphic material in the film.

"He's a World War II buff," Brad said at the film's world premiere in Washington.

Some have criticised the film's stark brutality, but Brad claims when it comes to appropriate viewing, he comes from "another generation".

"The world is a beautiful place, but it's also a very violent place. We talk about it afterwards, so I'm not so opposed," the actor said.

Fury's director David Ayer earlier insisted he didn't pick gruesome scenes to shock viewers.

The filmmaker - who directed stars including Brad, Michael Pena and Shia LaBeouf in the drama and also wrote the movie - said he included moments such as a tank commander's head being blown off to show the reality of conflict.

"That was a very common thing that happened," said David. "There's countless stories of crews being inside tanks and then all of a sudden their commander's headless body drops into the tank and sprays blood everywhere. That was the hazard of being a tank commander, and that's why these guys were so brave."

Fury sees Brad as Don "Wardaddy" Collier, who leads a five-man crew inside a tank deep into enemy territory where they experience - and participate in - hellish acts of war.

Actor Michael, who plays tank driver Trini "Gordo" Garcia, said: "This is like the PG-13 version of what real war is like. Real war is not pretty. You can validate almost everything you see on screen. The pictures that we saw were horrendous. This is just a little bit of it."

David, a former US Navy submariner, did endless research, including interviewing veterans, enlisting military experts and studying real war footage.

"In my investigation of the war, I wanted to find circumstances that would help create the world and tell the story of what these five guys faced," he said. "I wasn't cherry picking horrible things just to be gratuitous. I wanted to know what this family could experience together that puts us in their shoes and tells us about that war."

And he said there isn't more carnage left on the cutting room floor.

"It's not like there's going to be a director's cut in six months," he said. "This movie is my director's cut. Sony really understood the movie and trusted me to make it."