Sam Mendes's First World War epic 1917 started life as a series of stories told to him by his grandfather, Alfred Mendes, as the Trinidadian-born soldier crisscrossed European borders with the British forces.

The production that came out of it — about two infantrymen tasked with reaching another division to warn them of a German ambush — is no slouch. It's won seven BAFTAS, earned 10 Oscars nominations, and made over $250 million US so far at the global box office. It's a fully British success story with a (mostly) British cast to match.

But behind the scenes, not everything was made in Britain. The film relied significantly on Canadian contributions for its historical accuracy, and the technique that allowed it — through complex planning, editing and camera work — to masquerade as one continuous, unedited shot.

Gord Beck, a map specialist at McMaster University in Hamilton, was one of those contributors. Hidden in a low-ceilinged, brightly lit back room of Mills Memorial Library, he manages the university's substantial online collection of maps from the First and Second World Wars.

'That's super cool'

The collection includes aerial photos, topographic and trench maps straight from the areas and battles they diagram, sometimes marked in bullet holes, mud and blood.

And one of them — more than 100 years old and lying on the table in front of Beck — played a significant role in Mendes's movie.

"That's super cool," he said, describing what it was like after he finally saw 1917. "Just the fact that you're touching this map ... and then you see somebody on the other side of the ocean, a famous person, actually using it in a film."

Gord Beck, map specialist at McMaster University, details the map that eventually ended up in the hands of Colin Firth on the set of Oscars frontrunner 1917. 1:25

The map is a British one. Dated April 23, 1917 at 6 p.m., it outlines France's Western Front near the end of the First World War around cities and villages like Écoust-St. -Mein, Arras and Croisilles. They're also all areas 1917's two protagonists must pass through, which led the film's production team to repurpose it.

Map collection's many uses

Printed off from McMaster's digital collection, it is visible in an opening scene as actor Colin Firth outlines the path Lance-Cpl. Tom Blake (Dean-Charles Chapman) and Lance-Cpl. William Schofield (George MacKay) must take to warn a division of soldiers of a German ambush.

Beck helps manage McMaster University's online map collection. With more 5,500 WWI and WWII maps, it is believed to be the largest such collection in the world. (Jackson Weaver/CBC)

Beck says members of the film's production team contacted him in early 2019 asking to use the map. They found it in McMaster's online catalogue of more than 5,500 digitized images, which has become an important resource for historical productions and period pieces.

"Right now we have the largest First and Second World War collection of maps and air photos in the world online," Beck said. "We've been called by multiple movie production companies to use our material."

McMaster purchased its core collection from European auctions in the late '60s. Most of the university's World War maps arrived in 2009, when the university received a grant from the Canadian Heritage ministry. Library staff began digitizing the collection in 2012 for inclusion in a free-to-use online catalogue.

It was mostly intended for academic and archeological work. A company in France uses the maps in conjunction with ground-penetrating radar to avoid subways or shopping malls being built over buried World War dugouts.

A map of the WWI's Western Front in France, repurposed as set dressing in Sam Mendes' film 1917. The map was used to outline German positions on April 23, 1917. (Jackson Weaver/CBC)

Pieces from the collection have also been featured in a Vimy Ridge Heritage Minute by Historica Canada, the Dan Aykroyd documentary Drawn to Victory, and 2014's Fury, starring Brad Pitt. Another upcoming Firth production, Operation Mincemeat, has also asked McMaster for permission to use 20 of their Second World War maps, Beck said.

Canadian production designer behind 1917's look

1917's unique, single-shot look also directly relied on the efforts of another Canadian: Vancouver-born production designer Dennis Gassner.

The seven-time Academy Award nominee built kilometres of trenches, towns and farms for the movie. He spent four months simply "walking" out the dialogue on location to measure the character's movement before even beginning to plan the sets.

(From left to right) Dennis Gassner poses with actor Dean-Charles Chapman, director Sam Mendes and actor George MacKay during the 2020 Oscars Nominees Luncheon at the Dolby Theatre in Hollywood, Calif. (Robyn Beck/AFP/Getty Images)

"We knew it was going to be kind of inch by inch planning, and that's basically how we did it," Gassner, 71, said in an interview.

"We had to measure it, we had to create it, and we had to draw it. We had to model it, we had to build it and then we had to shoot it."

1917 marks Gassner's fifth collaboration with Mendes. They collaborated on Road to Perdition and Jarhead, as well as Bond films Spectre and Skyfall. Gassner actually passed on the opportunity to work on the next Bond offering, No Time to Die, in order to develop 1917.

Inspiration for the continuous shot came from Spectre's opening Day of the Dead scene, which used similar editing techniques for the four-minute sequence.

That inspiration led to his Oscar nomination for production design, which he shares with set decorator Lee Sandales. But Gassner said it was something else that inspired him while working on the film.

As they were scouting locations in France, Gassner said he ended up on a tour at the Somme, the site of a historic First World War battle that saw casualties of more than 24,000 Canadian soldiers. He described hearing a familiar accent, pulling a young woman to the side and asking if she was Canadian.

She told him she was. She had visited the site because of its connection to Canadian history.

"All of a sudden, my DNA kind of stepped up into this realm of 'I'm invested now,'" Gassner said. "And I understand now why I had to do this film — because of my history.

"I needed to have something that was grounding for me, and that was one of the bases of that."