Perhaps more than any other historical event, World War II has provided fodder for Hollywood. From The Bridge on the River Kwai to Saving Private Ryan to Schindler’s List, directors keep turning to “the good war.” This year alone, Fury (in theaters this weekend), Imitation Game and Unbroken all feature World War II heroes and will all battle for Oscar buzz.
Fury director David Ayer, who is a veteran himself, wanted to distinguish his World War II film with an air of authenticity. The movie takes on a single day in April 1945, when the Allies had for all intents and purposes beaten Germany. But American soldiers were still fighting on the front and, some would argue, needlessly dying. Calling into question the glory of war, Ayer and the movie’s actors—including Brad Pitt, returning to the time period he visited in Inglourious Basterds—met with veterans to get more intimate details on the challenges of fighting in a tank crew, the Credits reports.
According to the vets, the life expectancy of a tank crew member was only six weeks. Ayer incorporated this and other details he learned from veterans into the movie, like that every fifth bullet from a gun’s machine is a tracer, which is ignited with a burning powder that glows brightly so the shooter can follow the trajectory of the bullet with the naked eye. The actors also learned that the soldiers would differentiate between outgoing and incoming artillery by the whistling sound a projectile make when coming towards you (but not away from you).
Read about the connection between reality and another WWII movie, The Monuments Men, here in TIME’s archives: George Clooney’s Art of War