Days after Hiroshima and Nagasaki, Washington tells the public how the bomb was built
Six days after Hiroshima and three after Nagasaki, the government had still not officially explained how the bomb worked. On August 12, 1945, the federal government released the Smyth Report, a public account of the Manhattan Project written by physicist Henry DeWolf Smyth at the request of General Leslie Groves. It explained the physics behind nuclear fission while deliberately leaving out the chemistry, metallurgy, and ordnance details needed to build a bomb. By mid-October it landed on the New York Times bestseller list.
The Smyth Report became the model the government would reuse for decades: publish the science, withhold the engineering. Smyth's own preface argued that self-government required an informed public, even on nuclear secrets. That argument still shapes American debates over declassification today.
QWhat did the Smyth Report deliberately leave out of its account of the bomb?
The report was written to explain the physics of nuclear fission while omitting the chemistry, metallurgy, and ordnance details an engineer would need to actually build a weapon. Smyth and the Military Policy Committee designed the document to cover only what was already common knowledge among scientists or easily worked out by a competent physicist. That meant readers got a genuine scientific education on how fission released energy, but nothing resembling a blueprint. The distinction let the government claim honesty without handing over the machinery of mass destruction.
QWhat dual purpose was the Smyth Report designed to serve beyond informing the public?
Beyond being the government's official account for ordinary citizens, the report doubled as a reference tool for scientists themselves, marking exactly which information had been declassified and which remained off-limits. Researchers across the country could consult it to know what they were now legally permitted to discuss or publish without running afoul of the Espionage Act. This second function mattered as much as the public-facing one, giving the scientific community a shared, government-sanctioned boundary line for postwar nuclear research and publication.
QWhat earlier role did Henry Smyth hold on the Manhattan Project before writing the report?
Smyth's involvement stretched back to early 1941, years before he authored the public report, when he joined the National Defense Research Committee's Committee on Uranium. He later moved into a more senior post as associate director of the Metallurgical Laboratory in Chicago, one of the project's key scientific hubs. That long insider vantage point, spanning the earliest theoretical uranium studies through full wartime production, made him the natural choice to write the project's first public account.
