LOS ANGELES - Brad Pitt's new war movie "Fury" offers a no-holds-barred view of warfare which some may find hard to stomach - but its director justifies the gore as straightforward realism.
A stuntman was injured by a bayonet during the making of the film, which includes multiple close-up scenes of slaughter, and which has already been turned into a video game.
"War is violent. It's all incredibly realistic," director David Ayer told AFP, adding that a lot of the movie's scenes are based on actual military after-action reports.
"The sad truth is that the US military in World War II in Europe executed a lot of prisoners. It was kind of endemic," he added.
The movie follows a five-strong Sherman tank crew, led by Pitt as battle-hardened army sergeant "Wardaddy," pushing behind enemy lines in the dying days of the war in Germany in 1945.
Hollywood A-lister Pitt last led a cinematic Nazi-killing team in Quentin Tarantino's 2009 "Inglorious Basterds," and like that film "Fury" includes its fair share of gory SS officer deaths.
The bloodletting starts from the opening scene, when Pitt's character stabs a German through the eye, and includes a summary execution which tests the scruples of the team's young rooky "Bible," played by Shia LeBeouf.
"The movie is about the moral toxicity of war, and how that violence impacts what's effectively this family, this ad hoc family of men trying to survive," said Ayer.
The director - whose past writing credits include 2001's Oscar-winning "Training Day" - said history has tended to ignore the savagery and randomness of warfare in the narrative of victorious Allies defeating ruthless Nazis.
"Because World War II was such a battle of good versus evil, and because the outcome of liberating Europe from slavery is such a positive outcome .. we reverse engineered the fighting itself into some sort of idea (that it) was cleaner, or black and white," he said.
To get the cast - also including Michael Pena, Logan Lerman and Jon Berthal - into the spirit the filmmaker put them through a military-style "boot camp" run by US Navy Seals, before starting the shoot.
And even while on set, Ayer made Pitt and the other actors have fistfights in between takes, to build team spirit.
"It bonded us," said Leouf told Jimmy Kimmel. "You can only get so much out in a conversation, with a bunch of boys in that kind of setting, fighting was really intimate," he said.
Ayer explained: "These are people who are mad scientists when it comes to breaking down a team and creating a team, and that was the exact purpose of it.
"The cast was fed into that process and the cast that came out of that, they were absolutely transformed individuals and it bonded them in a way that you really really feel on the screen."
The stuntman accident happened while filming a scene in which bodies were piled on the battlefield.
"They had rehearsed it and one guy was basically stabbing dummies, and accidentally stabbed his mate with a bayonet," said Ayer, adding that there were no permanent injuries.
The film's violence has been likened by some reviewers to shoot-em-up video games - and in fact a "Fury" tie-in has been included in online gaming website wargaming.com's "World of Tanks" series.
Ayer said the movie, opening in the United States this weekend, also has parallels to current conflicts, whether in Afghanistan or Iraq and Syria where a US-led coalition is battling jihadist fighters.
In the film "they are fighting an absolutely fanatical ideology that even in its death throes was lashing out in horrifc ways, like pressganging entire classrooms of children, and sending them to the front against tanks.
"All of these things happened in World War II .. suicidal fanaticism is obviously something that our present-day military struggles to deal with," added the director.