Stories from the set

The actors and technical staff were trained to work with equipment created a century ago by meteorologists who were almost the same age. The film used exact copies of the weather maps that were used in planning the Normandy landings.

In order to convey in the smallest detail the appearance of wartime maps and documents, the filmmakers specially selected vintage printing presses and other equipment.

The filmmakers recreated the exact topography of the beaches based on postcards and photographs of the area provided by residents of the United Kingdom, who did not even suspect what their family archives were needed for.

The film included newsreel footage that Anthony Maras, the director and screenwriter, initially did not intend to use. He did not want the picture to look like a historical documentary. Recalling Peter Jackson's documentary project They Shall Not Grow Old (2018), Maras colorized the archival footage. When selecting material in the archives, Maras and his assistants viewed 46 hours of wartime newsreel footage.

While scouting locations for the Allied forces headquarters, Anthony Maras considered over 100 options. At one point he even thought about using the very estate in Hampshire where the command was stationed during World War II, but it turned out that a military base is still located there. In the end, the filmmakers settled on the Rothschild country estate in Buckinghamshire.

While working on the film, the cinematographer, costume designer, and production designer drew on the color palette of hand-tinted frames from wartime newsreels.

Artist Dan Taylor recreated the map of the planned landing operation as meticulously as possible from the surviving original. He even reproduced the color palette exactly—the same colors on the original varied in brightness because the map sections had been ordered from different British printing companies. This was due to secrecy. The companies did not know what these sections were or what they were part of.

One of the editors who worked with the archival newsreel footage turned out to be the grandson of the meteorologist James Stagg, who is discussed in the film and was played by Andrew Scott.

For the role of Dwight Eisenhower, actor Brendan Fraser shaved his head. Before filming began, he read everything he could find about his character. Fraser did not part with biographical materials about Eisenhower throughout the entire shooting period and constantly suggested nuances and details that were absent from the script, which he believed made his character's portrayal fuller and more accurate.