Director Christopher Nolan had the idea for the film in the 1990s when he was sailing across the English Channel, and initially wanted to make a film that was completely improvised, but eventually decided to write a trim screenplay in 2015. As in his other films, Christopher Nolan decided against using a linear timeline for Dunkirk, blending together three different stories and shifting timelines throughout.
In spite of the ambitious scale and scope of the film's subject matter, Nolan wanted to limit the amount of CGI. For the aerial scenes and the scenes that took place on the water, Nolan filmed using props as well as real planes and ships from World War II. This made the film more authentic and ensured a visual language that was cohesive, consistent, and realistic.
Nolan wanted to tell a realistic story, so he kept the dialogue in the movie sparse and focused more on events and dynamics rather than psychological background information, exposition, or dialogue. Working with composer Hans Zimmer, Nolan created a suspenseful tone, one which vacillates between moments of hope and moments of despair. In an interview with Variety about the film, Nolan said, "I didn't view this as a war film. I viewed it as a survival story."
