By Jennifer Van Evra

Critics are already calling it the best film of the year — and perhaps the greatest war movie ever made.

Christopher Nolan has already directed some of Hollywood's biggest movies, among them The Dark Knight, Interstellar, Inception, Batman Begins and Memento — and now he's taking on his first-ever historically-based drama.

Dunkirk is a World War II thriller about the evacuation of hundreds of thousands of Allied troops from the French city of Dunkirk before Nazi forces could take hold. Tom Hardy, Kenneth Branagh and Mark Rylance co-star, and the score is by longtime Nolan collaborator Hans Zimmer.

The film is garnering rave reviews and perfect scores from critics, including a 98 percent on Rotten Tomatoes. "The Oscar race for Best Picture is officially on," wrote Peter Travers in his 4/4 review in Rolling Stone.

The film is being released this Friday, but it also has an intriguing backstory. Here are 11 fascinating facts about the film that's sure to be the most talked-about this summer:

Those are real ships
Nolan used real navy destroyers for the battle sequences instead of CGI. At one point there were 62 ships in the water during filming.

It's going to look great
Aiming for the best possible image quality, Nolan shot the film using a combination of 15/70mm IMAX film and Super Panavision 65mm film, and it will be the third major motion picture to be shown theatrically in 70mm. The other two were The Master (2012) and The Hateful Eight (2015). It's also the first major motion picture to use handheld IMAX cameras.

This is Nolan's second shortest film
Dunkirk was not only directed by Nolan, it was entirely written by him. He also wrote Following and Inception, and co-wrote all of his other films, with the exception of Insomnia. At 76 pages, the screenplay is roughly half the length of his other scripts, and the shortest feature screenplay he has written. It's also his shortest film since 1998's Following.

The idea came to Nolan a long time ago
Nolan came up with the idea for the film 25 years ago, when he and his wife sailed across the English Channel to Dunkirk. But he was concerned his lack of large-scale filmmaking experience would hamper the project, so he waited until he had several blockbusters under his belt before making the film.

The film was shot where the real action happened
The film was shot in Dunkirk, France, in the same location as the World War II evacuation. Other locations included Urk, Netherlands; Swanage and Weymouth in Dorset, England; and at the Point Vicente Interpretive Center and Lighthouse in Rancho Palos Verdes, California.

Dunkirk uses a lot of extras
The film employed over 6,000 extras. In one scene, a crane, a spitfire and 1,500 extras were used to recreate the evacuation of 338,000 allied soldiers.

The film did not use Michael Caine
Dunkirk is one of the few Christopher Nolan films that doesn't feature Michael Caine. Caine has been in the majority of Nolan's films including Batman Begins (2005), The Prestige (2006), The Dark Knight (2008), Inception (2010), The Dark Knight Rises (2012) and Interstellar (2014). The last time he wasn't featured was in 2002's Insomnia.

Nolan didn't cast Harry Styles because he was Harry Styles
One of the film's co-stars is Harry Styles of the hit boy band One Direction. Nolan insists, however, that Styles' fame wasn't the reason he was cast. "I auditioned literally thousands of young men with different combinations of young men," said Nolan. "And he had it."

The film is Nolan's first historical drama
All of his other films were fictional.

There isn't much dialogue
There is almost no dialogue in Dunkirk, and Nolan studied classic silent movies including Erich von Stroheim's Greed (1924), D.W. Griffith's Intolerance: Love's Struggle Throughout the Ages (1916) and F.W. Murnau's Sunrise (1927). Other films that Nolan says influenced Dunkirk included the war classic All Quiet on the Western Front, the breathtaking 1981 film Chariots of Fire, Ridley Scott's tension-fuelled Alien, Jan de Bont's 1994 nail-biting film Speed, and Alfred Hitchcock's 1940 film Foreign Correspondent for its cinematic suspense and visual storytelling.

The film is told from three perspectives
The film is told from three perspectives: the air (in planes), the land (on the beach) and the sea (on ships). "For the soldiers who embarked in the conflict, the events took place on different temporalities," Nolan told Première. "On land, some were stuck on the beach for a week. On the water, the events lasted for a day maximum; and if you were flying to Dunkirk, the British spitfires would carry one hour of fuel. To mingle these different versions of history, I had to mix the temporal layers. Hence the complicated structure, even if the story is very simple."

Dunkirk opens in theatres Friday.