Seven-time Oscar nominee Dennis Gassner (“Blade Runner 2029,” “Jarhead”) was in Alaska recovering from back surgery when he got an interesting email.

“Do not do the ‘Bond’ film,” it read. “I have a film that’s very ambitious. Sending script now.”

The note, Gassner recalls, was from director Sam Mendes, who he’d previously worked with on 2005’s “Jarhead” and 2012’s “Skyfall.” The film in question was “1917,” his World War I epic that’s now earned 10 Oscar nominations. Two hours after Mendes first sent over the screenplay, Gassner was on board.

From burning oil fields to bomb sites, and soldiers on the ground in Saudi Arabia, Gassner said his on-set building experiences from “Jarhead” proved beneficial in capturing the atrocities of war. But bringing Mendes World War I vision to life in “1917” still had its challenges.

“We were going to show things that were uncomfortable for the audience, but we were going to do it in a way that is artistic and tells the story for them,” Gassner said.

“1917” is set during the First World War and follows two young British soldiers (George MacKay and Dean-Charles Chapman) tasked with delivering a dangerous message that could save thousands of lives. For one scene, Gassner had to create a collapsing bridge for MacKay’s character Schofield to climb over. Gassner worked with location manager, Emma Pill to find the perfect location.

“I told her, ‘I don’t know what this is really going to be. I think it’s going to be a canal and a bridge,’” Gassner said.

Pill had put feelers out all over the United Kingdom to find the ideal spot, later sending Gassner photographs. After whittling the selection down to two possible locations, Gassner took a trip to Liverpool.

“I just sat there and thought it was impossible. I thought it was going to be costly, but it gave me a sense of what this would be like.” Gassner said. “I went up to Glasgow to the other location and figured it out in five minutes.”

From there, Gassner went back to the concept artist and presented the work to Mendes and cinematographer Roger Deakins.

Another scene that takes place at a burning church was created on the backlot at Shepperton Studios. Again, Mendes, Deakins and Gassner worked in close collaboration with the art department. Every step was choreographed to the script.

“It was only because of ‘Jarhead’ and ‘Skyfall’ that I knew how to destroy that set.” Gassner said. “We had done that in ‘Skyfall– when they’re running from the burning house.”

Deakins lit the scene while timed flares created shadows and Schofield runs through the devastation. The goal of the film was to sustain a feeling of imagining what it was like to be these soldiers. Through Deakins’ camera work and Gassner’s set building, Mendes thrusts us into the trenches and into war.

“I don’t know when I finally drew a breath,” Gassner said. “Maybe during the Cherry blossoms moment.”