A major part of director Christopher Nolan’s Oppenheimer was the security clearance trial of J. Robert Oppenheimer, but it wasn’t entirely clear why he was on trial. Oppenheimer is a deep-dive into the most important parts of J. Robert Oppenheimer’s life, from detailing his work on the Manhattan Project to examining the moral implications of inventing the world’s first nuclear weapon. To accomplish the latter, Nolan used a pivotal moment in Oppenheimer’s life: his security clearance trial. That sequence scrutinized Robert’s role in the Manhattan Project and his guilt after World War II, but it was easy to miss why the trial happened at all.

Robert’s security clearance trial served as a way to bring the characters of Oppenheimer, and many different figures from his life, together again in the film’s final minutes. The timeline of Oppenheimer, however, made that sequence a bit confusing. Since it spliced together moments from both Lewis Strauss’ nomination to the U.S. Cabinet in 1959 and Oppenheimer’s trial in 1954, the final moments of the movie were often disorienting. It was often hard to tell when things happened and what caused them, and that confusion certainly extended to the reason for Oppenheimer’s security clearance trial.

Oppenheimer Had A Security Clearance Trial Due To Accusations Of Communist Sympathies

Early on in Oppenheimer, a scene showed Robert conversing with members of the communist party, one of whom convinced him to send money to Spain via communist channels. Oppenheimer also began an intimate relationship with Jean Tatlock, who was a communist. On top of that, Oppenheimer was a very vocal liberal for much of his life, and while he wasn’t an official member of the communist party, he did openly sympathize with the party and some of their ideology. That was controversial even before the Manhattan Project, but by the time of his security trial, Oppenheimer’s ties to the communist party were downright scandalous.

Oppenheimer’s security trial took place in 1954 (via Encyclopedia Britannica), and by that point in American history, the Red Scare and the era of McCarthyism were well underway. Much of the nation was deeply paranoid about the rising power of the Soviet Union and communism after World War II. Anyone who was even remotely close to being a communist or communist sympathizer was considered a threat to national security. Since Oppenheimer had long history with the communist party, and since he had such a prominent position as part of the Atomic Energy Commission (AEC), the government suspended Oppenheimer’s security clearance, and Robert requested a hearing.

Lewis Strauss, the chairperson of the AEC, also partially caused Oppenheimer’s trial. Strauss had a few reasons to hate Oppenheimer, but it was mostly due to the fact that Robert had insulted him in public and, Strauss falsely believed, in private to Albert Einstein. To make sure that the government’s trial resulted in a massive blow to Oppenheimer’s career, Strauss made several moves. He convinced several people that Oppenheimer was a security risk (via Atomic Heritage Foundation). Strauss also convinced the FBI to surveil Robert and use their recordings against him, and he appointed Roger Robb as the trial’s prosecuting attorney, ensuring that Oppenheimer wouldn’t get an impartial hearing.

Oppenheimer Was Also Charged With Opposing The Hydrogen Bomb & Lobbying Against President Truman’s Commission

Oppenheimer’s communist ties were a big reason for the security hearing, but an equally important factor was his open opposition to the hydrogen bomb. After President Truman dropped atomic bombs on Hiroshima and Nagasaki, Robert became deeply guilty of his role in the Manhattan Project, and he also became fiercely opposed to advancing the technology of nuclear weaponry. While he was serving on the AEC, Oppenheimer also lobbied against the bomb even after Truman approved its development.

To the U.S. government and specifically Roger Robb, Oppenheimer’s switch in opinion on nuclear weapons seemed suspicious. The hydrogen bomb was being built specifically as part of America’s nuclear arms race during the Cold War with the Soviet Union. In Oppenheimer, Robb and others argued that Robert only opposed the hydrogen bomb because there was a chance it would be used against the Soviets, which they considered evidence of him being a communist sympathizer. They cited the fact that Oppenheimer never opposed the atomic bomb during its development to argue that he wasn’t actually opposed to the weapon itself, just its target.

Who Testified At J. Robert Oppenheimer’s Security Clearance Trial & Why

The witnesses who testified at Oppenheimer’s security clearance trial essentially had two main reasons for doing so: either to defend him or to damage his reputation. All the people who defended Oppenheimer had something positive to say, but they approached his defense slightly differently. Isidor Rabi and Vannevar Bush both commended Oppenheimer as an upstanding citizen and a good friend, and Bush specifically got very mad that he was on trial at all. Meanwhile, Kitty Oppenheimer played Robb’s game and turned his own words against him, while Leslie Groves explained that Robert was no worse than the current members of the AEC.

On the other side of the argument, the witnesses who testified against Oppenheimer attacked a few key parts of his character and his past. Ernest Lawrence didn’t actually testify at the trial, as he claimed he had colitis. Lawrence would have testified against Oppenheimer partially because he disagreed with Oppenheimer’s liberal views and because he feared Soviet influence. William Borden testified against Oppenheimer because he thought Robert was a communist, and had written a letter years prior saying so. Edward Teller turned on his colleague not because of Oppenheimer’s ties, but because he disagreed with Robert’s decision-making, which he saw firsthand during the Manhattan Project.

Oppenheimer’s Trial Outcome Explained: Why His Security Clearance Was Revoked & He Lost His AEC Position

After the testimony of the trial was over, the security board determined that Oppenheimer was a loyal American, but they also voted to deny renewing his security clearance. There were a few reasons the board reached that decision. Oppenheimer still had friendships and relationships with members of the Communist party, and those relationships were considered a security risk. He also gave some answers in his testimony that contradicted both the secret recordings and his previous actions, which made him seem unreliable. Lastly, the testimony of his friends and colleagues did not paint Oppenheimer in a very good light, which certainly hurt his chances.

The biggest reason Oppenheimer’s security clearance was revoked, however, was because the security trial had been decided before anyone gave their testimony. Oppenheimer had a strained relationship with the American government even before the Manhattan Project, mostly due to his liberal views and connection to communism. On top of that, Strauss wanted Oppenheimer off the AEC, and he told Robb to make sure that happened. Essentially, there was no way Robert would ever have kept his security clearance by the end of Oppenheimer.

It is important to note that the security trial was not a criminal trial, so Oppenheimer didn’t face any legal consequences for the verdict the board reached. He did, however, have his security clearance revoked, which essentially ruined his career. Without security clearance, Oppenheimer couldn’t work with the U.S. government or attend the AEC meetings anymore, which essentially ended his career as a nuclear physicist. The security trial came towards the end of both Robert’s career and Oppenheimer the movie, and it was one of the last major moments in both.

Sources: Encyclopedia Britannica, Atomic Heritage Foundation