Considered the “father” of the atom bomb for his work on the Manhattan Project during World War II, physicist J. Robert Oppenheimer famously said he had blood on his hands for his role in dropping two atom bombs on Japan. When he persisted in raising concerns about the rapid growth of nuclear weapons, federal officials revoked his security clearance, citing allegations that he was a Communist.

Political arguments over Oppenheimer, once among the fieriest disputes in American politics, resurfaced in December 2022 when President Joe Biden’s administration overturned the 1954 decision that revoked Oppenheimer’s security clearance, saying it resulted from a “flawed process.”

Despite his life’s dramatic twists and turns, Oppenheimer has seldom been fodder for popular entertainment. That is about to change. A new movie about Oppenheimer will bring to life the story of the brilliant scientist who devoted himself to the defense of American democracy, then came to regret his key role in the use and spread of nuclear weapons—only to be cast out by a government intent on quashing his views.

Starring Cillian Murphy as the physicist, Oppenheimer will be released today, July 21, in theaters nationwide. Other stars include Emily Blunt as Oppenheimer’s wife, Kitty, and Matt Damon as US Army Lt. Gen. Leslie Groves, who worked closely with Oppenheimer on the creation of the atom bomb and simultaneously investigated the scientist’s Communist ties. The director is Christopher Nolan, whose blockbusters over the past 15 years range from three Batman films to Dunkirk, a historical drama about the desperate evacuation of allied soldiers from that French port early in World War II.

Nolan created the new film with the help of historian Kai Bird, a former Nation assistant editor and coauthor, with Martin J. Sherwin, of American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer, which in 2006 won the Pulitzer Prize for Biography or Autobiography. Sherwin died in 2021.

American Prometheus presents a finely detailed and evenhanded account of Oppenheimer’s many connections with Communists, including those that arose through his wife and a mistress, Jean Tatlock, as well as his brother, Frank Oppenheimer, all of whom at one point or another were members of the Communist Party. Ultimately, after examining the evidence, American Prometheus concludes that J. Robert Oppenheimer was treated unjustly when his top secret security clearance was revoked in 1954.

When the Biden administration last year reversed that revocation, Bird told The New York Times: “I’m overwhelmed with emotion.… History matters and what was done to Oppenheimer in 1954 was a travesty, a black mark on the honor of the nation.”

Oppenheimer was a physics professor at the University of California at Berkeley when he was chosen in October 1942 to be the director of the highly secret Manhattan Project—tasked with building nuclear weapons.

At the time, FBI and War Department officials were well aware of Oppenheimer’s leftist associations. But with the US government aiding the Soviet Union in its fight against Hitler’s armies, Manhattan Project officials did not balk at hiring scientists with left-wing politics.

At the chief weapons laboratory in Los Alamos, N.M., Oppenheimer led teams of scientists and industrial experts in creating the atom bomb, which was first tested on July 16, 1945, at a site in the New Mexico desert.

Prior to the test, Oppenheimer called for dropping the bombs on Japanese cities and worked with a committee that recommended Hiroshima and Kyoto be targeted for bombing.

US planes dropped nuclear bombs on Hiroshima and Nagasaki in August 1945, killing as many as 210,000 people in the blasts and subsequent radiation poisoning. Oppenheimer told President Harry Truman three months later in the White House, “Mr. President, I feel I have blood on my hands.”

Oppenheimer began urging his fellow nuclear physicists to oppose development of the proposed “super” weapon, the hydrogen bomb, a position that angered physicist Edward Teller and others who supported the H-bomb project. Oppenheimer also joined with Republican former secretary of war Henry Stimson and other prominent figures in calling for international control of nuclear weapons. Oppenheimer’s emergence as a public critic of the rapid spread of nuclear weapons quickly earned him enemies.

After Dwight D. Eisenhower was elected president in 1952, Lewis Strauss, chairman of the US Atomic Energy Commission, objected to Oppenheimer’s continued work as a consultant on US nuclear weapons matters. Strauss bitterly objected to a recommendation by Oppenheimer that the Eisenhower administration adopt a policy of “candor” revealing the truth about the size of the American nuclear arsenal.

In May 1953, Strauss met with FBI Director J. Edgar Hoover to urge the agency to probe Oppenheimer’s Communist associations, and by late November Hoover had prepared a 69-page memo summarizing allegations about Oppenheimer’s associations with Communists (including his wife’s involvement with the CP) and adding a summary of the physicist’s “candor” policy.

One Eisenhower ally warned the president that Senator Joseph McCarthy, at that time raging in the capital against Communists in the government, might use Hoover’s memo to accuse the administration of lax security. Ike took action on December 2, 1953, instructing his national security adviser, Robert Cutler, and Strauss to block Oppenheimer from access to secret information.

Cutler, though, supported Oppenheimer’s candor policy. At the same time as he took action against Oppenheimer, Cutler was helping Ike craft his “Atoms for Peace” speech. Delivering that speech at the United Nations on December 8, 1953, Ike revealed some aspects of the US nuclear arsenal and called for sharing information about nuclear weapons and for international agreements limiting their spread. Eisenhower’s speech led directly to the creation of the UN’s International Atomic Energy Agency, which to this day plays a crucial role in limiting the spread of nuclear weapons.

Two weeks later, Strauss informed Oppenheimer that his top-secret security clearance was suspended. Oppenheimer appealed, but after a closed-door hearing in June 1954 the AEC voted 4-1 to uphold the revocation of this security clearance. A national debate erupted as conservatives hailed the decision for removing a Communist risk while liberal critics saw it as part of a conspiracy to silence Oppenheimer because of his outspokenness on the dangers of nuclear weapons.

Bird and Sherwin concluded in American Prometheus: “At the peak of McCarthyite hysteria, Oppenheimer had become its most prominent victim.”

Sixty-eight years later, in December 2022, that AEC decision was overturned when US Energy Secretary Jennifer Granholm ruled that it had been part of a “flawed process that violated the Commission’s own regulations.” She noted, for instance, that Oppenheimer’s attorney was denied access to important records on which the AEC based its decision.

“As time has passed, more evidence has come to light of the bias and unfairness of the process that Dr. Oppenheimer was subjected to while the evidence of his loyalty and love of country have only been further affirmed,” Granholm said.

Even today, some Oppenheimer case documents remain partly classified and remarkably time-consuming for historians to review. In 2017, I filed a request under the Freedom of Information Act to review Hoover’s 69-page memo. Six years later, in March 2023, the National Archives finally released to me a copy of the memo with more than 70 redactions, citing an exemption that permits the government to withhold parts of a document in order to protect a “confidential source.”

The redactions shielded the identity of multiple informants, including one who said Oppenheimer participated in a Communist Party meeting in fall 1940, and another who said Oppenheimer had “in effect, delayed or attempted to delay the development of the H-bomb.”

Now Christopher Nolan’s movie will bring new awareness to the Oppenheimer saga, and the viewing public will decide whether it expresses the tremendous significance of the Oppenheimer case for American democracy—and for humanity’s struggle to contain the terrifying risks and catastrophic effects of nuclear weapons.