LOS ANGELES (Reuters) - When writer-director David Ayer decided to tackle the "beaten-to-death" World War Two movie genre with "Fury," he decided to make it an intimate affair for his cast led by Brad Pitt.
"When I told people I was going to make a World War Two movie, the eyes rolled, you hear the groan," Ayer recalled. "It's really the study of a family that happens to live in a tank and kill people."
"Fury," out in U.S. theaters on Friday, follows five men led by hardened war veteran Wardaddy (Pitt), overcome with fatigue and trucking along in Nazi Germany during the final months of World War Two.
"My (motive) is bringing a cast together and turning them into a family, turning them into brothers," Ayer said. "I haven't really seen that level of intense character study in a World War Two movie, and I felt like it was time for that."
Made for an estimated $80 million by Sony Corp's Sony Pictures Entertainment, "Fury" is an intimate story amid war-torn battlefields. It is projected to open with $25 million at the U.S. box office, according to BoxOffice.com.
Joining Pitt in the tank are actors Shia LaBeouf, John Bernthal, Michael Pena and Lerman, who all underwent an intensive military boot camp to research and bond.
"It's really tough," said Pena. "From the rations to waking up early to being sleep deprived, you're really having to rely on the other person to get through."
Pena, who previously worked with Ayer on 2012 police drama "End of Watch, jokingly compared working with the director to a root-canal dental procedure.
"It's always scary to do a David Ayer movie because what he likes is to make somebody uncomfortable and film that," he said.
The experience was new for 22-year-old Lerman, best known for young adult movies such as "Percy Jackson" and "The Perks of Being a Wallflower," who said he learned a lot about his physical and emotional limits.
"It was very humbling to think about the people that actually have to train like that," Lerman said.
Ayer said LaBeouf, who has more recently made headlines for bizarre antics including wearing a paper bag on his head for an art installation, "worked his ass off" to prepare for the role of God-fearing gunner Boyd "Bible" Swan.
"The crazy Shia rumors are fun, but the boring truth is he just did a lot of prep to play this character," Ayer said. "He doesn't showboat, and he's so powerful and understated."
Much of the film takes place in enclosed spaces and the violence, which is often bloody and prolific in battle scenes, aims to give context to the harsh and jarring conditions that scar the men.
"The reality of modern warfare and mechanized warfare is people are just mangled," Ayer said. "I have to show what they're reacting to and what they've seen for years, to understand the effect it's had on them."
(Reporting by Piya Sinha-Roy; Editing by Ken Wills)