The movie, which has its European premiere today at the close of the London Film Festival, follows a tank crew as it pushes behind enemy lines in the dying days of the war in Germany in 1945.
"It was not a film about sides," Pitt told reporters. "For me it was a film about that accumulative psychic trauma that every soldier carries to some extent."
He added: "This film is about the soldiers' exhaustion from the cold, hunger and the accumulative effect on a daily basis. We took that to heart.
Pitt, along with a number of other actors in the film, gave his support to last month's international "Invictus Games" for injured veterans, which took place in London.
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"I learnt a lot from this film," the 50-year-old said, adding that his role as battle-hardened army sergeant "Wardaddy" was "a real study in leadership".
"Because of this, I am now a better father," said Pitt, who has six children with actress Angelina Jolie.
He also admitted he became rather attached to the Sherman tank in which he and his team spent much of the film.
The film's director, David Ayer, said Pitt spent a lot of time in the tank on set.
"It was like his eagle's nest where he would look down on us," he said, to which the actor quipped: "It was the best view.