Nolan’s film is most directly misleading about actual history when Oppenheimer is portrayed as getting sidelined, starting at the end of the Los Alamos sequence when it is suggested that, despite his usefulness to the military and the government, they are only interested in Oppenheimer’s technical abilities and not in his advice on other matters. It is further implied that in the film’s postwar period, Oppenheimer becomes marginalized, in part because Strauss is the sort of person who actually controls policy. This is wrong on several levels. Oppenheimer was much closer to the policy process during World War II than the film depicts, including in the targeting of the atomic bombs (and not just from a technical perspective). The film’s implication of distance between Oppenheimer and the government officials involved in dropping the atomic bomb is inaccurate; they all saw eye to eye, and Oppenheimer personally endorsed the idea that the bombs ought be dropped on “urban areas” without warning. He even suggested, after the Trinity test, ways in which the bomb designs could be modified to use more of their scarce nuclear fuel, so that there would be many more bombs ready to drop on Japan (Groves rejected this suggestion for the first bombs). Many years later, well after Oppenheimer had died, Strauss told an interviewer that these scientists during World War II felt a “compulsion to use the bomb—an obsession,” and while one should be wary of the source, in this case I think he was right.
In truth, Oppenheimer enjoyed tremendous influence in the atomic energy establishment after World War II. The chairman of the Atomic Energy Commission for its first, formative years was not Strauss but David Lilienthal, a liberal New Dealer who considered himself a close friend of Oppenheimer’s and a political ally. Oppenheimer’s views did not always carry the day, but one cannot really describe him as sidelined until Eisenhower became president in 1953, and then only because Strauss was made AEC chairman (Strauss’s anti-Oppenheimer campaign, whatever its deep motivations, began in earnest when he feared that Eisenhower would be charmed by Oppenheimer’s way of thinking). One can see how this makes a less clean narrative about Oppenheimer and early nuclear policy, and one can see as well why Nolan probably felt that jumping from 1945 to 1949 worked better for an already long film.