DreamWorks Pictures and Universal Pictures announced today that principal photography will commence on 1917, written and directed by Academy Award®-winning filmmaker, Sam Mendes, on April 1, 2019.

The film follows two young British soldiers (Captain Fantastic’s George MacKay; Game of Thrones’ Dean-Charles Chapman) on a single day at the height of World War I.

Joining MacKay and Chapman are Mark Strong (The Imitation Game, Zero Dark Thirty), Andrew Scott (Spectre, Sherlock), Richard Madden (BBC’s Bodyguard, Cinderella), Daniel Mays (Fisherman’s Friends, Rogue One), Adrian Scarborough (The Madness of King George, Christopher Robin), Jamie Parker (Harry Potter and the Cursed Child), Nabhaan Rizwan (Informer), Claire Duburcq, with Colin Firth (The King’s Speech, the Bridget Jones franchise) and Benedict Cumberbatch (The Imitation Game, Doctor Strange).

Mendes, who will direct and wrote the screenplay with Krysty Wilson-Cairns (Penny Dreadful) produces the film with Pippa Harris (Revolutionary Road, Away We Go)—his partner at Neal Street Productions—along with Jayne-Ann Tenggren (Spectre, the upcoming The Rhythm Section) and Callum McDougall (Mary Poppins Returns, Skyfall). Co-producing is Michael Lerman. The film will begin principal photography next week, shooting on location in England and Scotland.

The creative team helping to bring this story to the screen includes cinematographer Roger Deakins (Blade Runner 2049, Skyfall); production designer Dennis Gassner (Bugsy, Road to Perdition); costume designer Jacqueline Durran (Anna Karenina, Darkest Hour); editor Lee Smith (Dunkirk, The Dark Knight); and composer Thomas Newman, who has created the scores for six previous Mendes films, including Skyfall, Road to Perdition and American Beauty.

The film is being produced by Neal Street Productions for DreamWorks Pictures and Universal Pictures, and will be released by Universal Pictures domestically on December 25, 2019. Universal and Amblin Partners will distribute the film internationally, with eOne distributing on behalf of Amblin in the U.K.

1917 marks a reunion for Mendes and DreamWorks Pictures. The British director made his first feature, American Beauty, under the DreamWorks label, followed by two other productions—Road to Perdition and Revolutionary Road.

There’s no looking away. The battlefield drama 1917 will play out in a surprising form—as if it were one continuous shot, tracking two British soldiers as they race through a carnage-strewn landscape to deliver a message that might save 1,600 lives.

George MacKay (of 11.22.63 and Captain Fantastic) and Dean-Charles Chapman (Tommen Baratheon on Game of Thrones) play Schofield and Blake, who are given orders to cross enemy territory to hand-deliver vital news that can be conveyed no other way. The film runs one hour and 50 minutes, and the story plays out in real time.

“It was fundamentally an emotional choice,” director Sam Mendes told Vanity Fair. “I wanted to travel every step with these men—to breathe every breath with them. It needed to be visceral and immersive. What they are asked to do is almost impossibly difficult. The way the movie is made is designed to bring you as close as possible to that experience.”

The American Beauty and Skyfall director cowrote the script with Krysty Wilson-Cairns (Penny Dreadful) and spent nine months preparing with veteran cinematographer Roger Deakins (an Oscar winner for 2017’s Blade Runner 2049) to make sure the shots and scenes were matched and timed seamlessly as they moved between locations while shooting this spring.

This behind-the-scenes video illustrates some of the challenges they faced, from making sure the late-day lighting remained consistent as the story unfolded to disguising the transitions between cuts. “What cuts?” Mendes answered coyly when asked about techniques for hiding them.

This type of approach has been attempted before, notably Hitchcock’s Rope in 1948, which played out entirely in one room. The 2011 horror-thriller Silent House and 2014’s Birdman pushed the technique further, one moving in and around a woodland home and the other circulating through Manhattan’s theater district.

What differentiates 1917 is its epic scale, journeying across a vast and chaotic outdoor landscape while remaining intimately focused on its two central characters. Along this odyssey they encounter other characters played by Benedict Cumberbatch, Claire Duburcq, Colin Firth, Richard Madden, Andrew Scott, and Mark Strong.

“The movie is essentially linear, and moves through a huge variety of different locations,” Mendes said. “From the trenches, to No Man’s Land, to open countryside, farmland, orchards, rivers, woods, and bombed-out towns. It bears witness to the staggering destruction wrought by the war, and yet it is a fundamentally human story about two young and inexperienced soldiers racing against the clock. So it adheres more to the form of a thriller than a conventional war movie.”

Mendes also provided some more insight into the story: “It is set in northern France during the spring of 1917, just at the point the Germans had retreated to the newly built and massively fortified Hindenburg Line. The British troops woke up one morning to find that the Germans had simply disappeared. There was a period of terrified uncertainty—had they surrendered, withdrawn, or were they lying in wait? It is across this mostly abandoned and shattered landscape that our two men have to journey. The Germans had destroyed anything of value—burnt down the towns, taken most of the civilians, chopped down the trees, and they had left behind booby traps, snipers, and a few other unexpected surprises.”

Designing the locations required just as much precision timing as the script for each set piece to connect. “Every location had to be exactly the correct length for the scene. We had to walk every step the characters would take long before we designed the sets and built them. I’ve never rehearsed a movie for as long, or in such detail.”

Most of the film was shot on Salisbury Plain in southern England, the same sloping grassland region where Stonehenge stands. “But we also shot at Glasgow docks in Scotland, on the River Tees in the north of England, and constructed nearly a mile of trenches at Bovingdon Airfield near London,” Mendes added.

1917 also required some technical innovation, and Mendes said it couldn’t have been made without the development last year of the new Arri Alexa Mini LF (for “large format”), which is significantly lighter and more compact than other cinematic cameras. “We talked about every camera move, every rig, every stylistic choice,” Mendes said. “Roger also felt that we needed a camera to be invented which could fit into some of these impossibly tight physical spaces. Thanks to Arri, we got exactly this.”

To keep the cast and crew on track, the filmmaker said, two scripts were needed: “One with dialogue, descriptive prose, screen directions, the usual…and then an additional script made up entirely of schematics and maps—showing exactly where the camera would move and when, where the actors would be moving, which rig we would be shooting on and how we would move from one location to the next.”

Mendes will be at New York Comic Con on Thursday for a panel further showcasing how they pulled it off. 1917 opens in limited release on December 25 and expands wide on January 10.