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Building the hydrogen bomb

By Patrick Coffey

Even before the Manhattan Project began, Edward Teller found the idea of building the Super (a hydrogen bomb) irresistible. After the Project’s end, Teller prepared a fifty-nine-page report, “A Prima Facie Proof of the Feasibility of the Super,” which he presented at an April 1946 conference at Los Alamos. He concluded, “It is likely that the Super bomb can be constructed and will work . . . within two years.” Most of those who had attended the conference found that claim incredible, because they had seen nothing to support it.

In 1949, the Atomic Energy Commission voted 3-2 to oppose development of the Super, based on the advice of its General Advisory Committee, who objected that it represented “the policy of exterminating civilian populations.” Senator Brien McMahon, a conservative Republican, took the AEC report to the Joint Chiefs of Staff and read it aloud to them, commenting as he went. Not surprisingly, the Joint Chiefs issued their own recommendation in favor of development.

Truman had appointed a three-man special committee to advise him on the Super — AEC Chairman David Lilienthal (opposed), Secretary of Defense Louis Johnson (in favor), and Secretary of State Dean Acheson (undecided). Johnson sent the Joint Chiefs’ recommendation directly to Truman, bypassing Lilienthal and Acheson. When the three met with Truman on 31 January, he had already decided. “What the hell are we waiting for?” he asked. Lilienthal timed the meeting: seven minutes.

Truman had had a tumultuous five years. He had taken office in April 1945. When Japan had surrendered that August, the United States was alone at the top: Europe, Japan, and China were in ruins; the Soviet Union had lost twenty million dead and seemed exhausted; but America was undamaged and rich, and it alone had the atomic bomb, a weapon so powerful that it seemed to make all others obsolete.

Then Stalin imposed Communist governments on almost all the territory that his troops occupied. The fourth postwar year had been particularly dark. On 29 August 1949, the Soviet Union exploded its first atomic bomb, something that most thought would not happen for years. On 1 October, Mao proclaimed the People’s Republic of China, and the remnants of the Nationalist forces retreated to Taiwan. And just days before Truman’s meeting to decide on the hydrogen bomb, he learned that Klaus Fuchs had admitted that he had been a Soviet spy during the Manhattan Project. His betrayal would soon be public, and Truman knew that many would see it as the explanation for the Russians’ bomb. The Communists seemed to be overtaking the United States on every front, and America’s moment alone at the top was ending.

In the midst of this storm of bad news, Truman announced on 31 January 1950, that he had directed the AEC to “continue with its work on all form of atomic energy weapons, including the so-called hydrogen or super-bomb.” Truman’s announcement was nothing like Roosevelt’s 1942 decision to build an atomic bomb. First, Truman’s announcement was public, whereas Roosevelt’s decision was secret; second, in 1950 no one knew if a fusion bomb was even possible, whereas in 1942 the physics of a fission bomb were well enough understood that success was nearly certain; third, fusion bombs (if they were physically possible) would be so powerful that they might destroy the world, whereas atomic bombs had at least some military utility; and finally, Truman’s announcement was political, whereas Roosevelt’s decision was military. Before his announcement, Truman did not ponder the technical problems or America’s strategy. Given all his bad press, he just needed to look tough.

Then came the breakthrough — although whose breakthrough remains a matter of dispute. In December 1950, physicist Stanislaw Ulam’s wife found him staring out the living room window. “I found a way to make it work,” he told her. Ulam thought an atomic bomb would compress hydrogen fuel rapidly enough to start a fusion reaction.  Teller had considered compression many times, and he insisted it would make no difference: the fusion reaction would occur faster, he said, but the tank holding the hydrogen would also explode faster, exactly cancelling any advantage. In his conversations with Ulam, however, he realized he was wrong. The only compression that he had previously considered was from the shock wave and mass due to chemical explosives, but he now realized that an atomic bomb would also exert radiation pressure, which traveled at the speed of light. Ulam’s scheme would work, Teller decided, but not exactly as Ulam explained it. Teller and Ulam wrote a report crediting themselves jointly for the work done.

Teller would spend the rest of his life denying Ulam’s role. He had spent ten years as a voice crying in the wilderness for his Super, and he was not about to cede any credit for the breakthrough idea. Between 1955 and 2001, he wrote five different accounts of the genesis of the idea of fusion by compression. For most people, memory blurs as time passes, but not for Teller. He recalled new details in each version, new conversations with participants who appeared in one story and then disappeared in another. But each of Teller’s versions came to the same conclusion: he, not Ulam, deserved the credit.


In hindsight, none of the moral or technical arguments against the Super would have made any real difference, even had they convinced Truman. The Soviet Union was hard at work on its own hydrogen bomb and would have succeeded eventually, which would have kicked off a crash American program that also would have succeeded.

The test of the Teller-Ulam hydrogen bomb took place on the 1st of November, just days before the 1952 presidential election. It was an unqualified success: it had been expected to yield five megatons, but it yielded twice that—about five hundred times as powerful as the Hiroshima and Nagasaki bombs. The fireball was three miles wide. The AEC filmed the explosion, added music and a narrator, and played the result on commercial television.

Patrick Coffey is a Visiting Scholar in the Office for History of Science and Technology at the University of California, Berkeley. He is the author of American Arsenal: A Century of Waging War and Cathedrals of Science.

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Image credit: The explosion of the hydrogen bomb, 1952. Photo by U.S. Department of Energy. Public domain via Wikimedia Commons.

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