Special effects supervisor Scott R. Fisher watched World War II films and documentaries to find reference points for the film that were based in reality. Prop prototypes were often 3D printed. Costume designer Jeffrey Kurland and his team cut and stitched the clothing for the film in the United States, manufacturing it for the main cast and thousands of extras. Production designer Nathan Crowley ordered around thirty military wristwatches from Hamilton Watch Company, each analog with a digital countdown.