Battles & Wars › Cold War › Nuclear weapons and deterrence
Hydrogen bomb
Ivy Mike, November 1, 1952; Tsar Bomba 1961· Invention or discovery· Weapons, armor & warships
Well documentedSolid records, physical evidence or scientific consensus.
A thermonuclear weapon that uses an atomic explosion to fuse hydrogen atoms, releasing hundreds of times the energy of the Hiroshima bomb.
See it on the Battles & Wars map →What happened
A hydrogen (thermonuclear) bomb uses an atomic-bomb 'trigger' to heat and squeeze hydrogen fuel until its atoms fuse, releasing far more energy. Edward Teller and Stanislaw Ulam found a workable design at Los Alamos in 1951. The first test, Ivy Mike, vaporized an islet at Enewetak Atoll on November 1, 1952, with about 10 megatons, some 700 times Hiroshima. The Soviets tested a true two-stage bomb in 1955; their Tsar Bomba of 1961, about 50 megatons, remains the largest explosion humans have ever set off.
Why it matters
It removed any practical ceiling on a weapon's power. One bomb could destroy any city, which made all-out war between the superpowers suicidal and deterrence the central idea of strategy.
How we know
Declassified test records and films, seismic and fallout measurements, and memoirs of Teller, Andrei Sakharov and others. The 1954 Castle Bravo fallout that sickened Japanese fishermen and Marshall Islanders is well documented.
Still debated
Credit for the key idea is still argued, Teller versus Ulam, as is how much Soviet designers gained from espionage versus their own work.
Connections (4)
▸Manhattan Project led to the far more powerful Hydrogen bombWell documented
The connection
Even during the Manhattan Project, Edward Teller pushed for a 'Super' bomb using fusion. After the Soviets tested an atomic bomb in 1949, President Truman ordered a crash program in January 1950 over the objections of Oppenheimer's advisory committee. The atomic bomb itself became the trigger that ignites the fusion fuel.
When and how
Berkeley summer study, 1942, where Teller raised the idea; Truman's decision on January 31, 1950; the Ivy Mike test, November 1952.
How we know
Declassified Atomic Energy Commission records, the General Advisory Committee's October 1949 report and participants' memoirs document the path.
Debates and open questions
Whether the US could have negotiated a mutual ban on H-bombs before testing, as some scientists urged, is a long-standing debate.
▸Hydrogen bomb raised the stakes of Nuclear weapons and deterrenceWell documented
The connection
Atomic bombs were measured in thousands of tons of TNT; hydrogen bombs in millions. A single weapon could destroy a large city and spread fallout far beyond it, as Castle Bravo showed in 1954. This made all-out war self-destructive for both sides and pushed strategy toward deterring war rather than winning it.
When and how
Pacific and Soviet test sites, 1952–61: Ivy Mike (1952), Castle Bravo (March 1954), the Soviet RDS-37 (1955) and Tsar Bomba (1961).
How we know
Test records, fallout data, and Cold War strategic writings such as those of Bernard Brodie and Herman Kahn reflect the shift.
Debates and open questions
Whether nuclear deterrence actually kept the peace, or the world was lucky given several close calls, is debated among historians and strategists.
▸First electronic computers (Colossus, ENIAC) ran early calculations for the Hydrogen bombWell documented
The connection
The first major problem run on ENIAC, starting in December 1945, was a Los Alamos calculation testing Edward Teller's early design for a hydrogen bomb. Later computers at Princeton and Los Alamos ran the long simulations used to design the device tested as Ivy Mike in 1952.
When and how
ENIAC at the University of Pennsylvania, 1945–46, run by Los Alamos physicists Nicholas Metropolis and Stanley Frankel; later machines at Princeton and Los Alamos, 1951–52.
How we know
Los Alamos records and histories such as 'ENIAC in Action' (2016) by Thomas Haigh, Mark Priestley and Crispin Rope.
Debates and open questions
Calculations by Stanislaw Ulam's team, partly by hand, showed Teller's first design would fail; how much computers versus human insight drove the final design is debated.
▸Los Alamos Laboratory designed the first Hydrogen bombWell documented
The connection
At Los Alamos in early 1951, mathematician Stanislaw Ulam and physicist Edward Teller worked out how an atomic explosion's radiation could compress fusion fuel. Lab scientists, with Richard Garwin drafting the engineering design, built the 82-ton Ivy Mike device, tested in 1952. A rival lab, Livermore, was founded that year.
When and how
Los Alamos, New Mexico, 1950–52; the Teller–Ulam report of March 1951; the test at Enewetak Atoll, November 1, 1952.
How we know
Declassified Los Alamos reports, Garwin's later disclosed role, and histories such as Richard Rhodes's 'Dark Sun' document the work.
Debates and open questions
How much credit belongs to Teller versus Ulam is still argued; Teller often played down Ulam's role.