Secrets of the Manhattan Project Leaked 1500 Times During World War II

Project Information Secret Bomb

The World War II program to develop an atomic bomb was the largest secret project ever undertaken by the U.S. government. But newly-declassified documents reveal how it hard it was to keep things secret as the weapon neared completion. Information leaks were everywhere, even in church sermons.

Trinity Test plutonium bomb image courtesy of Truman Library.

These detailed accounts have been made public on the website of the Department of Energy, which has posted the 36-volume, official history of the Manhattan Project, which had been commissioned by General Leslie Groves in late 1944. Among the most intriguing set of documents, released last month, is the volume about intelligence and security, which reveals:

"Since September 1943, investigations were conducted of more than 1,500 'loose talk' or leakage of information cases and corrective action was taken in more than 1,200 violations of procedures for handling classified material…. Complete security of information could be achieved only by following all leaks to their source."

Counterintelligence officials had their work cut out for them.

Efforts to keep a lid on atomic energy research had begun even before the Manhattan Project had started. In 1939, refugee scientists—mindful of the growing threat posed by Nazi Germany—urged their U.S. colleagues to undertake voluntary censorship of published studies concerning uranium fission. Initially, they rejected the idea—but as one European country after another fell to the Germans in 1940, the U.S. scientific community came to understand the importance of self-censorship. The Division of Physical Sciences of the National Research Council established a committee that succeeded in convincing most scientists to withhold publication of papers on sensitive subjects.

Still, occasional newspaper articles wrote about the potential applications of uranium fission in warfare. One such article, sympathetic to the plight of Europe, appeared in the March 18, 1941 edition of the Montana Standard:

It is known that there is enough power in one portion of uranium-235 the size of a pear to shoot the Empire State Building in the air with the speed of a rocket. It would be more than two million times as possible as one 1,000-pound air bomb of the type used by the Nazis in bombing London.

But nature has used her usual foresight in guarding such potential annihilation. Scientists admit it is impossible to separate uranium-235 from uranium-238. It is not that science has not figured out a method. It has. But the apparatus would be so complicated there is not now in existence enough scientists to set it up, even though they were to work a lifetime doing it.

We might say, quite frankly, that our scientists have disillusioned us.

Although physicists continued to play up the "impossible task" of separating sufficient amounts of uranium-235 to construct a bomb, reports and rumors of such a secret weapon continued to pop up in the press. Finally, in 1943, the director of the wartime Office of Censorship sent a special request to editors and broadcasters to not report on any rumors of "secret weapons" and to withhold any information on:

But, the greatest challenge to secrecy was the expansion of the Manhattan Project itself. As noted in the book, Counterintelligence in World War II:

The modest security system sufficed until, in the spring of 1942, with the start of the uranium program's rapid expansion ( via ).

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