on notice that dissent was no longer tolerated. On December 16, 2022, United States Secretary of Energy Jennifer Granholm nullified the 1954 decision, saying that it had been the result of a "flawed process" and affirming that Oppenheimer had been loyal. Background Robert Oppenheimer Before World War II, J. Robert Oppenheimer had been professor of physics at the University of California, Berkeley. The scion of a wealthy New York family, he was a graduate of Harvard University, and had studied in Europe at the University of Cambridge in England, the University of Göttingen in Germany (where he had earned his doctorate in physics under the supervision of Max Born at the age of 23), and the University of Leiden in the Netherlands. As one of the few American physicists with a deep understanding of the new field of quantum mechanics, he was hired by the University of California in 1929. As a theoretical physicist, Oppenheimer had considerable achievements. In a 1930 paper on the Dirac equation, he had predicted the existence of the positron. A 1938 paper co-written with Robert Serber explored the properties of white dwarf stars. This was followed by one co-written with one of his students, George Volkoff, in which they demonstrated that there was a limit, the so-called Tolman–Oppenheimer–Volkoff limit, to the mass of stars beyond which they would not remain stable as neutron stars and would undergo gravitational collapse. In 1939, with another of his students, Hartland Snyder, he went further and predicted the existence of what are today known as black holes. It would be decades before the significance of this was appreciated. Still, Oppenheimer was not well known before the war, and certainly not as renowned as his friend and colleague Ernest O. Lawrence, who was awarded the Nobel Prize in Physics in 1939 for his invention of the cyclotron. But as an experimental physicist, Lawrence had come to rely on Oppenheimer, and it was Lawrence who brought Oppenheimer into the effort to develop an atomic bomb, which became known as the Manhattan Project. Brigadier General Leslie R. Groves, Jr., who became director of the Manhattan Project on September 8, 1942, met Oppenheimer at Berkeley, where Oppenheimer briefed Groves on the work done so far on the "Super" (thermonuclear) bomb. Oppenheimer told Groves on October 8 that the Manhattan Project needed a dedicated weapons development laboratory. Groves agreed, and after a second meeting