top of page




One of the very important aspects of The Manhattan Project was to keep it absolutely secret, as if other countries found out about the work that is being done to create an atomic bomb, consequences would likely not be in U.S. favour. The U.S. were successful in their secret-keeping, so much so that year later, the Head of the Government's Office of Censorship, Byron Price, had called The Manhattan Project to be the best-kept secret of the war.

Prior to the Hiroshima and Nagasaki bombings, according to a 1945 Life article, "probably no more than a few dozen men in the entire country knew the full meaning of the Manhattan Project, and perhaps only a thousand others even were aware that work on atoms was involved." The publication claimed that the additional 100,000 project workers "worked like moles in the dark." They watched massive amounts of raw materials enter factories with nothing coming out and monitored "dials and switches while behind thick concrete walls mysterious reactions took place" without knowing the purpose of their jobs. They were warned that disclosing the project's secrets would result in a 10 year prison sentence or a fine of US$10,000 (equivalent to around $169,000 in 2023).

The Manhattan Project's security measures were examined and evaluated in a covert study released by the U.S. Army in December of 1945. According to this report, The Manhattan Project was "more severely guarded than any other highly secret war development". The Manhattan Project's security framework was so extensive and thorough that, in the early years of the project, security investigators thoroughly screened 600 organizations and 400,000 potential employees for any security risks. Government administrators who assigned labour were occasionally the biggest employers in the country, but they only knew about the "Pasco secret project"; one even remarked that prior to Hiroshima, "we had no idea what was being made."














Personnel of Oak Ridge avoided inviting the same guests repeatedly since security personnel regarded any private party with more than seven individuals as suspicious and residents feared that US government operatives were covertly present.

Every coffin of anybody who died on the site during the project's active years was repeatedly opened for inspection, even though original inhabitants of the area were permitted to be buried in already-existing cemeteries. When entering and leaving project premises, everyone was examined, including senior military officers and their vehicles. One Oak Ridge worker later said that "if you got inquisitive, you were called on the carpet within two hours by government secret agents. Usually those summoned to explain were then escorted bag and baggage to the gate and ordered to keep going".

Despite being told that their efforts would help put an end to the war and possibly all future wars, the fact that they were unable to see or comprehend the results of their frequently boring tasks—or even just common side effects of factory work like smoke from smokestacks—and that the war in Europe ended without the aid of their labour led to serious morale issues among workers and the spread of numerous rumours. One manager from Oak Ridge would say the following after the end of the war:

"Well it wasn't that the job was tough … it was confusing. You see, no one knew what was being made in Oak Ridge, not even me, and a lot of the people thought they were wasting their time here. It was up to me to explain to the dissatisfied workers that they were doing a very important job. When they asked me what, I'd have to tell them it was a secret. But I almost went crazy myself trying to figure out what was going on."

Another employee would describe how, while working in a laundry, she would hold "a special instrument" against uniforms and listen for "a clicking noise" each day. It is only after World War II that she discovered that she had been carrying out the crucial task of using a Geiger counter to check for radioactivity of the uniforms after work with radioactive material. Oak Ridge would go on to establish a vast intramural sports league system, comprising 10 baseball teams, 81 softball teams, and 26 football teams, to boost morale among workers of Oak Ridge.



Voluntarily censorship on atom-related studies begun even before the official beginning of The Manhattan Project. American scientists stopped publishing any studies related to military in the wake of the outbreak of World War II in 1939, and in 1940, journals of science started requesting papers be cleared by the National Academy of Sciences. After publishing an article on atomic fission in The Saturday Evening Post on the 7th of September, 1940, William L. Laurence of The New York Times would discover that the issue had been requested to be removed by government officials in 1943.

This silence was, however, rather loud for the Soviets, and in April of 1942, the Nuclear physicist Gregory Flyorov pointed out to Stalin that there is a suspicious lack of articles on nuclear fission in American journals, and as a result, the Soviet Union would begin their journey for the creation of an atomic weapon.

The Manhattan Project was very closely guarded against potential leaking of information to the Axis nations, particularly Germany, who would use this information to speed their own nuclear programs or launch clandestine operations against it. In contrast, the Office of Censorship relied on the media to abide by a voluntary code of behaviour it issued, therefore the initiative first chose not to inform the office. Newspapers started reporting about significant building in Tennessee and Washington in early 1943 based on public documents, and the office started talking with the project about how to maintain secrecy. By June, The Office of Censorship would ask newspapers and broadcasters not to mention "atom smashing, atomic energy, atomic fission, atomic splitting, or any of their equivalents. The use for military purposes of radium or radioactive materials, heavy water, high voltage discharge equipment, cyclotrons."

The office would also go on to ask to avoid any discussion of "polonium, uranium, ytterbium, hafnium, protactinium, radium, rhenium, thorium, deuterium"; only uranium was sensitive, but was listed with other elements to hide its importance.



















Sabotage was a constant possibility, and it was occasionally suspected when equipment malfunctioned. There were some issues that were believed to be caused by negligent or unsatisfied workers, however there were no documented cases of sabotage carried out at the behest of the Axis. However, on the 10th of March, 1945, a Japanese fire balloon collided with a power cable, causing a power surge that forced the temporary shutdown of Hanford's three reactors. Security was rather challenging because there were so many participants. To deal with the security concerns of the project, a specialized Counter Intelligence Corps detachment was established.

By 1943, it was evident that the Soviet Union was clearly making an effort to sabotage the project. The chief of the Western Defence Command's Counter Intelligence Branch, Lieutenant Colonel Boris T. Pash, looked into possible Soviet espionage at Berkeley's Radiation Laboratory. Oppenheimer would go to notify Pash that he had been contacted by Haakon Chevalier, a fellow Berkeley professor, regarding providing secrets to the Soviet Union.

By far, the most successful Soviet spy was Klaus Fuchs, a member of the British Mission who played an important part at Los Alamos, so much so that The United States' nuclear cooperation with Britain and Canada suffered greatly after the revelation of his espionage activities in 1950. Later, other instances of espionage were discovered, which resulted in the detention of Julius and Ethel Rosenberg, David Greenglass, and Harry Gold. For many years, George Koval and Theodore Hall as well as other spies were staying in the shadows. Given that a lack of uranium ore served as the main obstacle to the Soviet Union's development of an atomic bomb, it is challenging to estimate the worth of the espionage. It is estimated that the espionage saved the Soviet Union from one to two years worth of time.



















The Manhattan Project had another task along with the creation of the atomic bomb; obtaining information regarding the German nuclear energy program. It was believed that the Japanese nuclear weapons program was not far advanced because Japan had little access to uranium ore, however there was initial fear that Germany was very close to developing its own weapons. A bombing and sabotage campaign was soon launched against heavy water plants in German-occupied Norway at the order of the Manhattan Project. To look into enemy scientific advancements, a small mission was established and jointly staffed by the Office of Naval Intelligence, OSRD, the Manhattan Project, and Army Intelligence (G-2), which also applied to situations not involving nuclear weapons. Major General George V. Strong, the Chief of Army Intelligence, chose Boris Pash to lead the group, giving it the codename "Alsos" (which, in Greek, means "Grove").

After the city of Rome was taken in June of 1944, the Alsos Mission to Italy interrogated the physics lab employees at the University of Rome. In the meantime, Pash established a joint American-British Alsos mission in London, led by Captain Horace K. Calvert, to take part in Operation Overlord, which was to take place at around the same time. Groves believed that the possibility that the Germans may try to sabotage the Normandy landings using radioactive poisons was sufficient cause to alert General Dwight D. Eisenhower and sent an officer to inform Lieutenant General Walter Bedell Smith, the general's chief of staff. Specialized tools were made, and troops from the Chemical Warfare Service were trained in their usage, all under the codename Operation Peppermint.

Pash and Calvert spoke with Frédéric Joliot-Curie on the activities of German scientists as the Allied troops advanced into Europe. They discussed uranium supplies to Germany with representatives of Union Minière du Haut Katanga. They located 30 tons of ore in France and 68 tons in Belgium. German detainee interrogations revealed Oranienburg, 16 km north of Berlin, was processing uranium and thorium, thus Groves organized its bombing on the 15th of March, 1945. Later. 11 tons of ore were taken from the WIFO (a Nazi company) by an Alsos team who travelled to Stassfurt in the Soviet Occupation Zone. In April of 1945, Pash oversaw Operation Harborage, a sweep behind enemy lines of the cities of Hechingen, Bisingen, and Haigerloch that served as the centre of the German nuclear research. Pash was in charge of a combined force at the time known as T-Force. The nuclear laboratories, as well as records, tools, and supplies like 1.5 tons of metallic uranium and heavy water, were all taken by this combined force.

Kurt Diebner, Otto Hahn, Walther Gerlach, Werner Heisenberg, and Carl Friedrich von Weizsäcker were among the German scientists that alsos teams rounded up. They were sent to England and detained at Farm Hall, a bugged home in Godmanchester. The Germans were compelled to acknowledge that the Allies had accomplished what they were unable to once the news of the bombings of Hiroshima and Nagasaki spread around the world.


Image provided by


Security signs 2 (OR) bw.jpg


Image provided by
Image provided by


Image provided by
bottom of page