If Cillian Murphy is the undisputed star of Oppenheimer, Robert Downey Jr can’t be far behind. His portrayal of Lewis Strauss – Washington insider, H-bomb hawk, and Oppenheimer’s nemesis – is fabulous: layered, serpentine, cynical, knowing, the Salieri to the great scientist’s Mozart. Downey Jr, who will almost certainly be nominated for the Best Supporting Actor Oscar next March, described the character as “someone who’s extremely subtle and plotting, who doesn’t have any punchlines, who’s only charming when he’s trying to manipulate or undermine”.

 “Amateurs chase the sun and get burned,” the character says at one point. “Power stays in the shadows.” And the performance has prompted many moviegoers to ask the same question: who, exactly, was Lewis Strauss?

The answer begins in an unusual place: the way he pronounced his surname, to rhyme with ‘horse’ rather than ‘house.’ The former was the pronunciation common in West Virginia, where he had been born, and he was as proud of his Southern roots as he was of his Jewish ancestry: “I knew men who had known [Confederate general] Robert E. Lee,” he said. In later years, some critics accused him of trying to downplay his Jewishness with this pronunciation, a charge which not only rankled him deeply but also touched on one of the three main reasons he ended up so disliking Oppenheimer. 

Strauss’s father was a successful shoe salesman in the state capital of Charleston, and Strauss himself was valedictorian (best student) in his high school graduation class. From this he would ascend to the highest ranks in Washington’s notoriously anti-Semitic political circles – rear admiral as a reservist, chairman of the Atomic Energy Commission (AEC), acting Secretary of Commerce – and had done so without ever disavowing his faith or reducing his activities within the Jewish community (he was involved with a huge number of Jewish organisations over the years).

In contrast, he saw Oppenheimer as somehow having left his Jewishness behind. Where Strauss was committed to his faith, Oppenheimer could seem largely indifferent to his. “Oppenheimer was Jewish, but he wished he weren’t and tried to pretend he wasn’t,” said Oppenheimer’s friend Isidor Isaac Rabi. Oppenheimer’s references came from a variety of cultures: he chose the name “Trinity” for the atom bomb test at least partly from John Donne’s Holy Sonnet XIV, which begins “Batter my heart, three-person’d God”, and his famous reference to “I am become Death, destroyer of worlds” is from the Bhagavad Gita, which he read in the original Sanskrit.

The second source of the men’s animus was political. Strauss was a conservative Republican who took a dim view of Oppenheimer’s leftist leanings and past flirtations with communism. When they sat on the AEC together in the late 1940s and early 1950s, Strauss tended to be much the more hawkish of the two, constantly pressing for rapid development of thermonuclear weapons and adamant that only maximum capability could provide effective deterrence.

For his part, Oppenheimer was not quite as opposed to second-generation nuclear bombs as the movie makes out, and the opposition he did hold was as much technical as moral. He preferred to keep on building atomic bombs for possible use on conventional battlefields, where a hydrogen bomb would be too destructive; though when he saw that such a bomb was possible, the scientific challenge of building one very much appealed to him.

The two men had such different mindsets that disagreement was perhaps inevitable. Oppenheimer the scientist, used to sharing and pooling research; Strauss the politician, suspicious of everyone and ancestrally paranoid about sharing information with even the US’s nominal allies, such as Britain and Canada, let alone the Soviet Union. As Strauss’s biographer Richard Pfau wrote: “Oppenheimer supported a policy of openness regarding the numbers and capabilities of the atomic weapons in America’s arsenal; Strauss believed that such unilateral frankness would benefit no one but Soviet military planners.” 

For a man like Strauss, the USSR was an existential threat to America in a way that Nazi Germany and Imperial Japan had never been: indeed, he would later say that “I did my best to prevent [the attack on Hiroshima]. The Japanese were defeated before the bomb was used.”

As that line might suggest, Strauss effectively pouring cold water on Oppenheimer’s creation, the third plank of the rivalry was an exceptionally personal one. Strauss was a proud man, a self-made millionaire who had amassed a fortune in merchant banking, and he bristled at what he perceived as Oppenheimer’s dismissiveness towards him. In a 1949 hearing on the question of whether exporting radioisotopes for medical purposes was a risk to national security, as Strauss had proposed, Oppenheimer appeared in his testimony to be mocking Strauss when he said that isotopes were “less important than, let us say, vitamins”. 

Even something as simple as Strauss’s 1947 offer to Oppenheimer of the directorship of independent research centre the Institute for Advanced Study – a scene we see depicted in the film – had come freighted with angst. Strauss, one of the institute’s trustees, had sought the job himself, but had been only fifth choice. Oppenheimer, of course, had been first. 

This triskelion – religious, political and personal – combined to play out in the later of Oppenheimer’s two timelines, when in 1954 Strauss convenes an AEC committee to withdraw Oppenheimer’s security clearance on fairly tenuous political and ideological grounds. 

As one of Strauss’s fellow commissioners said, “If you disagree with Lewis about anything, he assumes you’re just a fool at first. But if you go on disagreeing with him, he concludes you must be a traitor.” That kind of treachery was pretty much the accusation which Strauss made stick against Oppenheimer – “fundamental defects in his character” were among the phrases used – and that in turn ruined the scientist. “The hearings broke Oppenheimer’s spirit,” said Pulitzer Prize-winning historian Richard Rhodes. “He was never the same person afterwards.”

The year before that hearing, Oppenheimer had likened the two nuclear superpowers to “two scorpions in a bottle, each capable of killing the other, but only at the risk of his own life”. So too, perhaps, with Oppenheimer and Strauss. In 1959, Strauss’s treatment of Oppenheimer persuaded the Senate to block his appointment to the Cabinet, something which had not happened since 1925 and would not happen again until 1989. 

Strauss had been Eisenhower’s first choice for the role of Secretary of State for Commerce due to his experience on the AEC, as well as his financial background (unlike in the UK, cabinet members don’t need to be elected representatives at the time of their appointment). His blocking basically ended his government career: he was 63 at the time and effectively retired after that, at least from formal roles, though he was still reasonably active behind the scenes in the Republican party and remained close to both Eisenhower and Herbert Hoover.

Among the Senators who voted against Strauss was John F. Kennedy, who four years later as president would intend to help rehabilitate Oppenheimer by awarding him the Enrico Fermi Award for lifetime achievement in the development, use or production of energy. 

Fermi, who had created the world’s first nuclear reactor, had worked with Oppenheimer on the Manhattan Project, and the prize was worth $50,000 ($500,000 in today’s money), but Kennedy never got to make the presentation himself. Instead it was Lyndon Johnson who oversaw the ceremony in December 1963, less than a fortnight after Kennedy’s assassination in Dallas.

When Strauss died in 1974, his obituary made the front page of the New York Times. Strauss, the piece said, puzzled most observers. “He was, on the one hand, a sociable person who enjoyed dinner parties and who was adept at prestidigitation; and, on the other hand, he gave the impression of intellectual arrogance. He could be warm-hearted yet seem at times like a stuffed shirt. He could make friends yet create antagonisms.” 

Those words could equally have applied to Oppenheimer himself, despite the two men’s myriad differences: and that is perhaps as good an explanation for their antagonism as any.