“Dunkirk” features a prestigious cast, including Tom Hardy (“The Revenant,” “Mad Max: Fury Road,” “Inception”), Mark Rylance (“Bridge of Spies,” “Wolf Hall”), Kenneth Branagh (“My Week with Marilyn,” “Hamlet,” “Henry V”) and Cillian Murphy (“Inception,” “The Dark Knight” Trilogy), as well as newcomer Fionn Whitehead. The ensemble cast also includes Aneurin Barnard, Harry Styles, James D’Arcy, Jack Lowden, Barry Keoghan and Tom Glynn-Carney.