The Secretary of Energy on Friday nullified a 1954 decision to revoke the security clearance of J. Robert Oppenheimer, a top government scientist who led the making of the atomic bomb in World War II but fell under suspicion of being a Soviet spy at the height of the McCarthy era.
In a statement, the Energy Secretary, Jennifer M. Granholm, said the decision of her predecessor agency, the Atomic Energy Commission, to bar Oppenheimer’s clearance was the result of a “flawed process” that violated its own regulations.
As time has passed, she added, “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.”
Historians, who have long lobbied for the reversal of the clearance revocation, praised the vacating order as a milestone.
“History matters and what was done to Oppenheimer in 1954 was a travesty, a black mark on the honor of the nation,” Mr. Bird said. “Students of American history will now be able to read the last chapter and see that what was done to Oppenheimer in that kangaroo court proceeding was not the last word.”
Alex Wellerstein, a historian of science at Stevens Institute of Technology in Hoboken, N.J., called the reversal long overdue.
“I’m sure it doesn’t go as far as Oppenheimer and his family would have wanted,” he said. “But it goes pretty far. The injustice done to Oppenheimer doesn’t get undone by this. But it’s nice to see some response and reconciliation even if it’s decades too late.”
In April and May of 1954, after 19 days of secret hearings, the Atomic Energy Commission revoked Oppenheimer’s security clearance. The action blocked Oppenheimer’s access to the government’s atomic secrets and brought his career to a humiliating end. Until then a hero of American science, he lived out his life a broken man and died in 1967 at the age of 62.
Historians and nuclear experts who studied the declassified material — roughly a tenth of the hearing transcripts — said it offered no damning evidence against him, and that the testimony, on balance, tended to exonerate him.
“It’s hard to see why it was classified,” Richard Polenberg, a historian at Cornell University who edited a much earlier, sanitized version of the commission’s hearings, said in 2014 “It’s hard to see a principle here — except that some of the testimony was sympathetic to Oppenheimer, some of it very sympathetic.”
An eccentric genius fond of pipes and porkpie hats, Oppenheimer grew up in an elegant building on Riverside Drive in Manhattan, attended the Ethical Culture School and graduated from Harvard in three years. After studies in Europe, he taught physics at the University of California, Berkeley.
As a young professor, he crashed his car while racing a train, leaving his girlfriend unconscious. His father gave the young woman a Cézanne drawing.
In the 1930s, like many political liberals, Oppenheimer belonged to groups led or infiltrated by Communists; his brother, his wife and his former fiancée were party members.
In the 1940s at Los Alamos in New Mexico, in great secrecy, he led the scientific effort that devised the atomic bomb. Afterward, as chairman of the Atomic Energy Commission’s main advisory body, he helped direct the nation’s postwar nuclear developments.
Oppenheimer’s downfall came amid Cold War fears over Soviet strides in atomic weaponry and Communist subversion at home. In 1953, a former congressional aide charged in a letter to the F. B.I. that the celebrated physicist was a Soviet spy.
Troubled by the allegation, President Dwight D. Eisenhower ordered “a blank wall” erected between Oppenheimer and any nuclear secrets.
A key element in the case against Oppenheimer was derived from his resistance to early work on the hydrogen bomb, which could explode with 1,000 times the force of an atomic bomb. The physicist Edward Teller had long advocated a crash program to devise such a weapon, and told the 1954 hearing that he mistrusted Oppenheimer’s judgment. “I would feel personally more secure,” he testified, “if public matters would rest in other hands.”
No evidence came to light that supported the spy charge. But the security board found that Oppenheimer’s early views on the hydrogen bomb “had an adverse effect on recruitment of scientists and the progress of the scientific effort.”
The material declassified in 2014, which was released by the Energy Department, suggested that Oppenheimer’s opposition to the hydrogen bomb project rested on technical and military grounds, not Soviet sympathies.
Richard Rhodes, author of the 1995 book “Dark Sun: The Making of the Hydrogen Bomb,” said the records showed that making fuel to test one of Teller’s early H-bomb ideas would have forced the nation to forgo up to 80 atomic bombs.
“Oppenheimer was worried about war on the ground in Europe,” Mr. Rhodes said in an interview at the time. He saw the need for “a large stockpile of fission weapons that could be used to turn back a Soviet ground assault.”
Experts who examined the declassified transcripts said they shed much light on the famous case. Dr. Polenberg of Cornell, for example, expressed bewilderment that 12 pages of testimony from Lee A. DuBridge, a friend and colleague of Oppenheimer’s who discussed the atomic trade-offs and the European standoff with the Soviet Union, had remained secret for 60 years.
“A difference of opinion doesn’t mean disloyalty,” Dr. Polenberg said in 2014. “It’s hard to see why it was redacted.”
Dr. Polenberg also pointed to 45 pages of declassified testimony from Walter G. Whitman, an M.I.T. engineer and member of the Atomic Energy Commission’s advisory body.
“In my judgment,” Mr. Whitman said of Oppenheimer, “his advice and his arguments for a gamut of atomic weapons, extending even over to the use of the atomic weapon in air defense of the United States, has been more productive than any other one individual.”
Asked his opinion of Oppenheimer as a security risk, he called him “completely loyal.”
In her Friday statement, Ms. Granholm said her department, as a successor agency to the Atomic Energy Commission, had been entrusted with the responsibility to correct the historical record and honor Dr. Oppenheimer’s “profound contributions to our national defense and the scientific enterprise at large.”
“I am pleased,” she added, “to announce the Department of Energy has vacated the Atomic Energy Commission’s 1954 decision In the Matter of J. Robert Oppenheimer.”