Josh Hartnett Boards Starry Cast of Christopher Nolan's Upcoming 'Oppenheimer' Movie

Josh Hartnett is set to join the already star-studded cast of Christopher Nolan's latest film Oppenheimer, which follows the invention of the atomic bomb during World War II.

The Black Hawk Down actor, 43, signed on for the biopic that already counts Emily Blunt, Matt Damon, Robert Downey Jr., Florence Pugh and Rami Malek amongst its stars, according to Deadline. Cillian Murphy will take on the title role playing J. Robert Oppenheimer, the scientist in charge of the Manhattan Project which led to the creation of the atomic bomb.

Blunt will reunite Murphy — her costar in A Quiet Place — to play Oppenheimer's wife, Katherine, while Pugh will take on the part of Jean Tatlock, a member of the Communist Party who has an affair with the scientist, according to The Hollywood Reporter.

Downey Jr. will portray Lewis Strauss, who served two terms as the chairman of the U.S. Atomic Energy Commission and played a major part in the development of nuclear weapons in the United States, while Damon is set to play Leslie Groves, who was in charge of the construction of the Pentagon and directed the Manhattan Project, according to IMDb. Malek joined the cast in a still unknown role.

Universal called the film — which will be released on July 21, 2013 — an "epic thriller" about "the enigmatic man who must risk destroying the world in order to save it," Variety reported.

Oppenheimer observed the Trinity test in New Mexico, where the first atomic bomb was detonated in July 1945. A month later, the weapons were used in the atomic bombings of Hiroshima and Nagasaki, Japan.

In 1954, Oppenheimer lost his security clearance after a controversial hearing which ended the physicist's role in U.S. government and policy.

Nolan will direct and co-write the screenplay with Kai Bird and Martin J. Sherwin, authors of the book American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer.

Oppenheimer is not the first time Hartnett has taken part in a World World II film — he also starred in 2001's Pearl Harbor.

Last month, Hartnett opened up during an appearance on the Australian talk show The Project about those early days of his career and his life in the spotlight.

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"The biggest thing for me was, I really enjoy making films, but the industry itself was overwhelming for a 21-year-old kid," Hartnett revealed.

"The press was a little bit different back then, there was paparazzi around every corner, you couldn't really go anywhere without being sort of harassed," he added.