A modern wartime tragedy: Dunkirk director Christopher Nolan says in a new interview that he basically didn't know who Harry Styles was before casting him in the period piece.

In an interview with BillboardNolan — who's directed the likes of Memento, Inception and several Batman features — said Styles earned his part in the film, and that his casting was by no means a testament to his fame.

"I don't think I was that aware really of how famous Harry was," he said. "I mean, my daughter had talked about him. My kids talked about him, but I wasn't really that aware of it. So the truth is, I cast Harry because he fit the part wonderfully and truly earned a seat at the table."

Still, Styles said filming was certainly stressful, and noted filming Dunkirk was a huge undertaking.

"I'd say realizing the scale of the production was very overwhelming," he said. "I think whatever you imagine kind of a giant film set to be like, this was very ambitious even by those standards. You know the boats and the planes and the volume of bodies...it was pretty amazing."

Dunkirk, which follows the evacuation of Allied soldiers from Dunkirk, France in 1940, opens July 20.

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