Clint Eastwood’s thing now is dramatizing notable acts of American heroism — he did it with Chris Kyle in American Sniper, and airline pilot Chesley “Sully” Sullenberger in Sully. But while both of these movies starred A-list actors, for his latest about the soldiers who saved a train full of passengers from a terrorist in 2015, Eastwood is conducting an experiment: The soldiers are playing themselves.

The subjects of The 15:17 to Paris, Anthony Sadler, Alek Skarlatos, and Spencer Stone, were on a train from Brussels to Paris when it was boarded by an ISIS terrorist with a box cutter, a pistol, and AK-47, and enough ammunition to kill everyone onboard. The four soldiers charged the gunman, saved the train, and made international headlines for their heroism. Eastwood told EW that casting each of them as themselves was an “interesting experiment.”

I looked at a lot of very good actors who could possibly have done the job. But I kept looking at the faces of these young men — “boys,” I call them. I thought these faces were unique. It just struck me that it would be an interesting experiment. It could be bold or reckless, depending on how it comes out. [Laughs] Anyway, they were enthusiastic about trying it, so we went with them, and I think people will be a little surprised. But as we got going, I started looking at other people who were involved. I thought, I wonder if they’d all like to come back? One thing led to another.

When the terrorist Ayoub El Khazzani boarded the train, he shot one man in the back of the neck, who played dead, though survived. When Khazzani’s rifle jammed, the three soldiers immediately jumped up to subdue him, one putting him in a chokehold and another beating him on the head with the butt of his rifle until he was unconscious. Along with several other passengers who helped, the three of them were awarded France’s Legion of Honour.

In the early evening of August 21, 2015, the world watched in stunned silence as the media reported a thwarted terrorist attack on Thalys train #9364 bound for Paris—an attempt prevented by three courageous young Americans traveling through Europe. The film follows the course of the friends’ lives, from the struggles of childhood through finding their footing in life, to the series of unlikely events leading up to the attack. Throughout the harrowing ordeal, their friendship never wavers, making it their greatest weapon and allowing them to save the lives of the more than 500 passengers on board.

The 15:17 to Paris arrives in theaters February 9.

More From ScreenCrush