Spencer Stone, left, plays himself in "The 15:17 to Paris." (Warner Bros. Pictures/Warner Bros. Pictures)

“Lord, make me an instrument of your peace,” young Spencer Stone says as he kneels for his nightly prayers in Clint Eastwood’s new fact-based thriller, “The 15:17 to Paris.” The boy will grow up to fulfill that wish as a young man, when he and his two childhood buddies from Sacramento, Alek Skarlatos and Anthony Sadler, help thwart a terrorist attack in 2015 on a train headed to Paris from Amsterdam. But coming from a kid who wears camouflage to Catholic school, houses a small arsenal of paintball guns, and dreams idly of the “brotherhood” of war, the Prayer of Saint Francis sounds a little like Samuel L. Jackson’s hit man citing Ezekiel 25:17 in “Pulp Fiction,” an ominous promise of bloody, cleansing righteousness.

For Stone, an instrument of peace could be a gun or a fist or the jujitsu chokehold that he used to subdue Ayoub El-Khazzani, a terrorist armed with an assault rife and 270 rounds of ammunition. “The 15:17 to Paris” treats Stone’s story as a case of divine destiny, following a timeline from childhood to young adulthood that seems littered with obstacles but, in retrospect, follows a straight line. Stone talks about being “catapulted” toward some fateful moment where his purpose will be revealed to him and Eastwood hangs on every word. In the simplest possible reading, Eastwood sees Stone and his buddies as heroes, the type of guys who are willing to assert themselves when the lives of others are on the line.

The film is a tribute to them, just as Eastwood’s last two efforts, “Sully” and “American Sniper,” are tributes to Chesley “Sully” Sullenberger, the US Airways pilot who pulled off an emergency landing on the Hudson River, and Chris Kyle, the marksman who tallied 255 kills over four tours of duty in the Iraq War. Where many directors might have asked Stone, Skarlatos and Sadler to serve as technical consultants, Eastwood chooses to have them play themselves, gambling that their authenticity will make up for any deficiencies in their acting chops. The combination of a director famous for shooting scenes in very few takes with nonactors who need some coaching seems like a recipe for disaster, but their stilted performances are part of the point. These are real men and “The 15:17 to Paris” sometimes has the quality of a documentary about a European vacation that takes a drastic turn.

Sullenberger, Kyle and the three guys in “The 15:17 to Paris” are Eastwood heroes, straight shooters in the figurative and often literal sense. They carry over from Eastwood’s career as an actor, too, from the Man With No Name in “A Fistful of Dollars,” “For a Few Dollars More” and “The Good, the Bad and the Ugly,” to Dirty Harry in the 1971 thriller and its sequels, to the veteran Secret Service agent in “In the Line of Fire.” We recognize the type in many of the films Eastwood has directed, too — westerns such as “High Plains Drifter,” “The Outlaw Josey Wales,” and “Unforgiven” — and his historical dramas, such as his extraordinary duo of 2006 World War II pictures, “Flags of Our Fathers” and “Letters from Iwo Jima.”

Anthony Sadler, Alek Skarlatos and Stone as themselves in “The 15:17 to Paris.” (Warner Bros. Pictures/Warner Bros. Pictures)

A stoic minimalism has been Eastwood’s mantra from the start. When Sergio Leone, his director on the Man with No Name films, was asked to compare Eastwood with Robert De Niro, whom he directed in “Once Upon a Time in America,” Leone said the two actors “don’t even belong to the same profession.” He said Eastwood “throws himself into a suit of armor and lowers the visor with a rusty clang” and “it’s exactly that lowered visor which composes his character.” This was Leone’s way of acknowledging Eastwood as more movie star than suffering thespian, but the remarkable continuity between Eastwood the actor and Eastwood the director tells the story. The Eastwood hero is sturdy and unchanging, as reliable a magnum force as he is an imposing one.

Yet still waters run deep. Accepting the responsibility of thwarting a terrorist or serving four tours of duty or landing a commercial airliner on water means accepting the burdens, too. Beyond the obvious understanding that death could be a consequence of heroic action, there are also the traumas of survival. In “Flags of Our Fathers,” the six servicemen made famous for raising the flag at Iwo Jima have to live with the fictions of their memorialization, on top of the horrors of a war that continued after the famous photograph. The Chris Kyle of “American Sniper” spends so much time immersed in war and death that re-acclimating to everyday life becomes impossible. Even Sully, who saved everyone on his aircraft through nonviolent means, is visited by nightmares of what might have happened if his decision or execution turned out to be tragically wrong.

Clint Eastwood on the set of "Flags of Our Fathers." (Paramount Pictures/Paramount Pictures)

Eastwood’s masterpiece, “Unforgiven,” could be read as an apologia for his previous work, the laments of a career-long gunslinger. As his William Munny, a former bandit turned vigilante, descends on Big Whiskey, Wyo., to collect a bounty on two cowboys accused of disfiguring a prostitute, the film treats him as a condemned man, made hollow by the corrosive buildup of a sinful life. But Munny’s cause in “Unforgiven” is nonetheless a righteous one, just like that of every other Eastwood hero, and he’s seeking some sliver of redemption from a murderous past.

“It’s a hell of a thing, killing a man,” he tells his young and skittish partner. “Take away all he’s got and all he’s ever gonna have.” It’s not something many people are capable of doing — or capable of living with if they do.

“The 15:17 to Paris” doesn’t get far into the aftermath of the train attack, which Eastwood shoots with a messy freneticism that feels truer to real life than the choreographed violence of most thrillers. He cannot speculate how Stone, Skarlatos and Sadler will handle the fallout. He can only note that they were willing to act as instruments of the Lord’s peace and accept whatever the cost to their bodies and souls.