Before “Inception,” before “The Dark Knight,” before even his breakout film, “Memento,” director Christopher Nolan took a boat trip through the waters near Dunkirk, the French beach famous for its pivotal role in World War II. The story of Dunkirk, in which British civilians risked their lives to pilot 700 boats across the English Channel and bring home more than 300,000 imperiled Allied troops, unfolded during the late spring of 1940, before America entered the war. For a Brit like Nolan, however, Dunkirk is almost holy ground, akin to Pearl Harbor or the World Trade Center in the United States.

“Making that trip and realizing how difficult and arduous crossing the Channel in a small boat is — even without going into a war zone — that was something that really stuck with me,” says Nolan. “And it really cemented my interest in the events of Dunkirk, and my admiration for the people who helped with the evacuation.”

On Friday, July 21, roughly 20 years after that mid-1990s journey, Nolan’s “Dunkirk” will arrive on the big screen. Filmed partly at Dunkirk itself with IMAX and 65 mm cameras, the movie re-creates an evacuation effort remarkable for its cooperation between a battered military and a self-sacrificing citizenry. Nolan, who also wrote the screenplay, tells the story in three segments — on land, on sea and in the air — which unfold simultaneously albeit in different time frames: one week, one day and one hour, respectively. “Dunkirk” stars Mark Rylance (“Bridge of Spies”) as a determined boatman, Tom Hardy (“Mad Max: Fury Road”) as an RAF pilot and Kenneth Branagh as a naval commander who helps spearhead the undertaking known as Operation Dynamo.

With its historical setting and emphasis on period detail, “Dunkirk” marks a departure for Nolan, whose best-known films have been set in unreal or fantastic worlds: the Gotham City of “The Dark Knight,” the surreal dreamscapes of “Inception,” the altered 19th century of “The Prestige.” It’s an unexpectedly short film — a lean 107 minutes — from a director who tends to make epics. “Dunkirk” also contains few major stars, save perhaps Hardy, and relies instead on a cast of mostly newcomers and lesser-knowns. Its protagonist, a young soldier named Tommy, is played by Fionn Whitehead, a 20-year-old actor making his feature-film debut.

That brings up a question: Can this non-star-driven film live up to Nolan’s previous successes at the box-office? Very few World War II movies have become bona fide blockbusters in the years since “Saving Private Ryan” (1998), which rode to $480 million worldwide with help from stars Tom Hanks and Matt Damon. What’s more, the story of Dunkirk may not have a built-in emotional resonance with Americans, let alone with viewers in important overseas markets like China.

Nolan seems aware that “Dunkirk” could be a gamble, and he sounds anything but worried. “I think Warner Bros. understood this story. And they understood that — as one of most famous British stories of all time — there was no question of Americanizing it any way,” Nolan says. “The deal I made with them was to make the film as efficiently as possible, and to try to give them a huge scale and a universal story that anyone could relate to.”

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“Dunkirk” is certainly universal in one sense: It has very little dialogue. Virtually no information is given about any character’s back story, and one shell-shock victim, played by Cillian Murphy, never even reveals his name. Most of the soldiers trapped on the beach are identifiable mainly by their faces, particularly the mysterious Gibson (Aneurin Barnard) and the tightly wound Alex (Harry Styles, formerly of the boy band One Direction, in his first acting role). Even the film’s lead actor, Whitehead, has only a handful of lines.

“I’ve got massive respect for the way Chris works,” Whitehead says of the filmmaker who plucked him from several hundred other actors during an old-fashioned open casting call. “He creates this very close, intimate feel on set and kind of helps you get to know everybody. You get close to the cast and crew a lot quicker. . . . He’s very hands-on, and I wouldn’t have had it any other way.”

“Dunkirk” will likely earn praise for its dazzling visuals and camerawork, but Nolan is looking for a deeper reaction from viewers as well. “I’m hoping to achieve a cumulative emotional effect through the film, by having you be engaged in a very intense struggle for survival,” he says. “Dunkirk is one of the great rallying stories about communal heroism. And I think that has a very powerful emotional force.”