In early 1951, Los Alamos scientists Edward Teller and Stanislaw Ulam devised a breakthrough that would lead to the hydrogen bomb [1]. Their design gave the United States an initial advantage in the Cold War, though comparable progress was soon achieved independently in the Soviet Union and the United Kingdom.

The technical details of the design breakthrough remain classified. Instead of discussing the technology, here I present the story of the disputes that quickly followed its conception—particularly over who deserved credit. Teller and Ulam were brilliant, forceful, often difficult men who held little affection for each other [2,3]. Their contrasting accounts, alongside recollections from equally remarkable contemporaries, reveal how scientific breakthroughs emerge from a volatile mix of cooperation, competition, and flashes of independent insight.

These were not idle quarrels: Teller pointedly refused to cosign the hydrogen bomb patent—withholding shared recognition—and declined to attend the 1952 Ivy Mike test in the Pacific. His absence was interpreted (at least in part) as a protest stemming from Los Alamos Scientific Laboratory Director Norris Bradbury’s decision to keep Teller from directing the Mike engineering effort—an entirely justified call...

...The Teller–Ulam paper holds a place in fusion history comparable to the 1940 Frisch–Peierls memorandum for fission (as described in Cameron Reed’s excellent article in the July 2025 Nuclear News, “The Frisch-Peierls Memorandum: A Seminal Document of Nuclear History” [4–6]). The hydrogen bomb fundamentally changed the world’s geopolitics. It contained Soviet ambitions through the rapid expansion of nuclear arsenals and the military-industrial complex, underpinned strategies such as Massive Retaliation, influenced arms control agreements, and eventually helped shape a global nuclear order—embodied in the Treaty on the Non-Proliferation of Nuclear Weapons and the spread of peaceful reactor technologies. That order, however, has been under strain in recent years [7]...

...Assessments of “who deserves credit” inevitably depend on whether one considers both phases of the solution: (1) Ulam’s initial concept and Teller’s radiation elaboration, and (2) Teller’s working out of the energetics. Both men, in their own retellings, acknowledged the two parts. Hans Bethe, in his detailed and fascinating history, also used this “two parts” framing [12]. Ultimately, any attempt to assign percentagesb is subjective.

The timeline was astonishing: just two and a half years from Truman’s directive to a full-scale thermonuclear test. It was even more extraordinary, in some ways, than the development of the fission bomb. The physics was more intricate; the computing tools were primitive, if trailblazing (ENIAC); and opportunities for experimental validation were limited. Its success was not assured. Unlike fission weapons, there were few intermediate tests to confirm progress. An exception came in 1951 with the Greenhouse George experiment, which produced the first sustained burning deuterium-tritium fusion plasma. Fuel was easier to obtain than fissile material but still demanded new industrial capacity, particularly for liquefying deuterium..