On July 4, 1945, the great atomic scientist Leo Szilard finished a letter that would become the strongest (and one of the very few) real attempts at halting President Truman’s march to using the atomic bomb – which was two weeks from its first test at Trinity – against Japanese cities.

It’s well known that as the Truman White House made plans to use the first atomic bombs against Japan in the summer of 1945, a large group of atomic scientists, many of whom had worked on the bomb project, raised their voices, or at least their names, in protest. They were led by the Szilard. On July 3, he finished a petition to the president for his fellow scientists to consider, which called atomic bombs “a means for the ruthless annihilation of cities.” It asked the president “to rule that the United States shall not, in the present phase of the war, resort to the use of atomic bombs.”

The following day, July 4, he wrote this cover letter (below). The same day, Leslie Groves, military chief of the Manhattan Project, wrote Winston Churchill’s science advisor seeking advice on how to combat Szilard and his colleagues. The FBI was already following Szilard. The bomb would be dropped over Hiroshima on August 6.

 

July 4, 1945

Dear _______________

Enclosed is the text of a petition which will be submitted to the President of the United States. As you will see, this petition is based on purely moral considerations.

It may very well be that the decision of the President whether or not to use atomic bombs in the war against Japan will largely be based on considerations of expediency. On the basis of expediency, many arguments could be put forward both for and against our use of atomic bombs against Japan.

Such arguments could be considered only within the framework of a thorough analysis of the situation which will face the United States after this war and it was felt that no useful purpose would be served by considering arguments of expediency in a short petition.

However small the chance might be that our petition may influence the course of events, I personally feel that it would be a matter of importance if a large number of scientists who have worked in this field went clearly and unmistakably on record as to their opposition on moral grounds to the use of these bombs in the present phase of the war.

Many of us are inclined to say that individual Germans share the guilt for the acts which Germany committed during this war because they did not raise their voices in protest against these acts. Their defense that their protest would have been of no avail hardly seems acceptable even though these Germans could not have protests without running risks to life and liberty. We are in a position to raise our voices without incurring any such risks even though we might incur the displeasure of some of those who are at present in charge of controlling the work on “atomic power”.

The fact that the people of the people of the United States are unaware of the choice which faces us increases our responsibility in this matter since those who have worked on “atomic power” represent a sample of the population and they alone are in a position to form an opinion and declare their stand.

Anyone who might wish to go on record by signing the petition ought to have an opportunity to do so and, therefore, it would be appreciated if you could give every member of your group an opportunity for signing.

Leo Szilard

 

What happened next? Well, the petition gained from than 180 signatures—Oppenheimer obviously not one, and actively discouraged others – but was then delayed in getting to President Truman by Gen. Leslie Groves, military head of the Manhattan Project, until the A-bombs were ready to use, in early August. Groves also commissioned a poll of atomic scientists, which found that over 80% favored a demonstration shot only – so he squelched that, too. Much more in my 2020 book: The Beginning or the End: How Hollywood – and America – Learned to Stop Worrying and Love the Bomb.

I’ve mentioned previously that my new award-winning film will start streaming, and screening on TV, from PBS on July 12. This week the companion e-book with the same title has been published: “The Atomic Bowl: Football at Ground Zero – and Nuclear Peril Today.” It’s just $5.79 and includes previously unpublished stills and material from the film and much more. Read more here. Thanks.

Thanks for reading Oppenheimer and the Legacy of His Bomb ! Subscribe for free to receive new posts and support my work.

Greg Mitchell is the author of a dozen books, including “Hiroshima in America,” and the recent award-winning The Beginning or the End: How Hollywood – and America – Learned to Stop Worrying and Love the Bomb, and has directed three documentary films since 2021, including two for PBS (plus award-winning “Atomic Cover-up”). He has written widely about the atomic bomb and atomic bombings, and their aftermath, for over forty years. He writes often at Oppenheimer: From Hiroshima to Hollywood.

https://www.antiwar.com/blog/2025/07/04/on-july-4-1945-the-man-who-tried-to-halt-the-atomic-bombings/

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Leo Szilard (1898-1964) was a Hungarian-American physicist and inventor.

EARLY LIFE

Leo Szilard was born Leo Spitz on February 11, 1898 in Budapest, Hungary. He developed an interest in physics at age thirteen and attended public school prior to being drafted into the Austro-Hungarian Army in 1917, where attended officer’s training school. However, influenza prevented him from an active duty assignment. After World War I ended, he left Hungary for Berlin in 1919.

In Berlin, Szilard studied Engineering at the Institute of Technology (Technische Hochscule). In 1921 he enrolled at the University of Berlin to study Physics under Max von Laue. Szilard earned his Ph.D. in August of 1922 and completed his postdoctoral work at the Kaiser Wilhelm Institute in Berlin. During his stay at the Institute he became close friends with Albert Einstein.

When Hitler rose to power in 1933, Szilard moved to England. He developed the idea of the nuclear chain reaction in 1933. While in England, Szilard also collaborated with many individuals and worked as a research physicist at the Clarendon Laboratory between 1935 and 1937. During this time, he visited the United States several times and by 1938 became a visiting lecturer there.

WORLD WAR II

In 1940 Szilard became an American citizen and moved to New York. He began working at Columbia University (Pupin Laboratories) where he collaborated with Enrico Fermi, Walter Zinn, and Herbert Anderson. At Columbia Szilard submitted his nuclear break-through manuscript titled: “Divergent Chain Reactions in a System Composed of Uranium and Carbon” in February of 1940.

When World War II started, Szilard became intensely concerned about the possible nuclear weapons development programs that could be initiated. As a result of these concerns, his work on atomic energy intensified. He led an effort to have all nuclear-related research data withheld from publication, to help prevent Germany from obtaining any information, or possibly creating an atomic bomb.

These concerns also prompted him, with the assistance of Eugene Wigner and Edward Teller, to contact Albert Einstein. After sharing his fears with Einstein and obtaining his consent, Szilard drafted a letter that Einstein signed. The now-famous Einstein Letter was subsequently delivered by Alexander Sachs to President Franklin D. Roosevelt in October of 1939. This letter outlined the possibility of achieving a nuclear chain reaction and its implications for the development of nuclear weapons for national defense. It also requested government support to conduct a large-scale experiment to prove whether or not a sustained nuclear chain reaction was possible.

President Roosevelt approved the funding and the project. Szilard began procuring suitable quality graphite and uranium, the necessary materials for constructing a large-scale chain reaction experiment. This experiment was successfully demonstrated on December 2, 1942 at the University of Chicago. This successful demonstration was partially the result of Szilard’s atomic theories, his uranium lattice design, and the identification and mitigation of a key graphite impurity (boron) through a joint collaboration with graphite suppliers.

Szilard was the chief physicist at the Chicago Metallurgical Laboratory from February 1942 to July 1946. He worked for Arthur H. Compton, the head of the Met Lab. Szilard helped build Chicago Pile-1, the first neutronic reactor to achieve a self-sustaining nuclear chain reaction. Szilard patented creating a neutron-based chain reaction in 1934 – although, as historian Alex Wellerstein explains, his ideas in the patent had some problems scientifically and would prove to be wrong in parts.

Szilard was very uneasy about the military’s dominant role in managing the Manhattan Project, complicated government administration, and flawed security regulations. He was very vocal about these issues as well as documenting them through his prolific letter writing.

Szilard viewed the development and eventual production of the atomic bomb as a necessary evil or counter-measure to the possibility of a German atomic bomb. After Germany surrendered and the war ended in Europe, he organized his colleagues to collectively voice the need to adopt limitations regarding the use of an atomic bomb. He drafted a letter and circulated it to the various Manhattan Project locations. The letter urged President Roosevelt to practice restraint in using the atomic bomb, but the letter was never forwarded to the President’s attention. Szilard realizing this, scheduled a meeting with Eleanor Roosevelt requesting that she personally pass the letter to the president. President Roosevelt died before the meeting with Eleanor could take place.

In June of 1945 the Franck Report was released. The Franck Report committee was appointed by Arthur Compton with James Franck as its head. Most of its contents was written by Eugene Rabinowitch, and signed by James Franck, Donald J. Hughes, J.J. Nickson, Eugene Rabinowitch, Glenn T. Seaborg, J.C. Steans, and Leo Szilard. This report outlined the possibilities and dangers of initiating or engaging in a nuclear arms race. In addition, the report also advocated for having a non-combat demonstration of the atomic bomb instead of first-use on a Japanese city.

On June 21, 1945 the report was presented to the interim committee appointed by President Harry Truman to advise him on the use of the bomb. The recommendation for a demonstration was rejected. Szilard followed by circulating another petition in July 1945 urging President Truman not to drop the atomic bomb on Hiroshima. The final version of this petition was signed by sixty-eight scientists assigned to the Met Lab. The petition was strongly opposed by General Leslie Groves. As a result, it never reached the president.

In September of 1942, President Truman advocated for the passage of the May-Johnson Bill, designed to place atomic energy in the ownership of the military. Szilard worked to help defeat this bill along with many Met Lab and Oak Ridge Lab scientists.

LATER YEARS

On June 1, 1946, Leo Szilard resigned from the Met Laboratory, to focus on molecular biology. He helped to found the Salk Institute for Biological Studies. Between 1946 and 1954, he served as a part-time professor at the Institute of Radiology and Biophysics (University of Chicago), a part-time advisor at the Office of Inquiry into the Social Aspects of Atomic Energy (University of Chicago), and a visiting professor of biophysics at Brandeis University.

In June of 1956, he became a professor of biophysics at the recently formed Enrico Fermi Institute for Nuclear Studies at the University of Chicago. Throughout the 1950s and early 1960s Szilard continued to focus on biological research that resulted in numerous scientific papers and articles. His theory on aging became a major subset of his research and was a reoccurring interest in his later years.

He applied for many patents, including one for the linear accelerator and cyclotron, and came up with many important scientific concepts, including the nuclear chain reaction and key ideas in thermodynamics. In 1955, Szilard and Enrico Fermi jointly received the patent for a neutronic reactor.

He continued his political activism, calling for international arms control, peaceful uses of nuclear energy, and improved U. S.-Soviet relations. In 1947, The Bulletin of the Atomic Scientists published a “Letter to Stalin” written by Leo Szilard. In the letter, he appealed to all world leaders to begin an open dialogue with the intent to exchange ideas to halt the rapidly escalating Cold War. In 1962, he founded the Council for a Livable World, warning of the threat of nuclear war.

Szilard’s political activities even inspired Albert Einstein and Bertrand Russell. As a result, the International Conference of Concerned Scientists was formed. The first conference took place in 1957 at Pugwash, Nova Scotia. The “Pugwash” conferences have continued to the present day. Between October 1959 and 1960, he conducted a series of interactions with Soviet Premier Nikita Khrushchev, culminating in New York with a two hour interview. During this interview, Szilard proposed the creation of a “Hot Line” between Moscow and Washington. The purpose was to foster and speed up communication between the Soviet Union and the United States. The “Hot Line” was implemented after the 1962 Cuban Missile Crisis and remains in use today.

In addition to Szilard’s research, and his dedication to nuclear, social, and political issues, he still found time to write. He wrote “The Voice of the Dolphins “in 1960. This book provides a futuristic, fictionalized, account where dolphins inherit the earth as a result of human civilization’s failure to be suitable caregivers of the planet. He also created an extensive series of historical tape recordings that archives his involvement in the Manhattan Project and other portions of his life.

Always a visionary, Szilard, sacrificing many years of his career and having no permanent post for himself, worked tirelessly to find suitable positions for many of the other scientists fleeing Germany. Often working by himself, at the detriment of his own safety and career, Szilard was responsible for numerous colleagues being offered positions. He organized several groups and worked with the Academic Assistance Council, a London-based group headed by Ernest Rutherford that helped refugee scientists and scholars.

Szilard continued his advocacy for global cooperation for the remainder of his life. In 1961 he completed a lecture tour to eight college campuses. On May 30, 1964, Leo Szilard died of a heart attack just three months after moving to La Jolla, California where he intended to continue his biological research as a Resident Fellow of the Sauk Institute.

For more information about Szilard, check out William Lanouette’s biography “Genius in the Shadows: A Biography of Leo Szilard, the Man Behind the Bomb” or watch an interview with Lanouette on “Voices of the Manhattan Project.”

Much of the information for this profile was provided by David Wargowski. In 2019, Wargowski and Dr. Henry Frisch created a Leo Szilard Exhibit located at the Albert A. Michelson Center for Physics Building of the University of Chicago.

 

https://ahf.nuclearmuseum.org/ahf/profile/leo-szilard/

 

Quick post here to report that Trump is getting blowback from his recent reference to Hiroshima and Nagasaki.

The mayor of Hiroshima, for example, has invited Trump to visit the city after his comments comparing the atomic bombings of 1945 to his own decision to strike Iran’s nuclear facilities.“That hit ended the war. I don’t want to use an example of Hiroshima, I don’t want to use an example of Nagasaki, but that was essentially the same thing,” he said.

Of course, for one thing, many (including yours truly) have argued that the atomic bombings did not “end the war” or in any case did not play the most pivotal role.

The remark, in any event, provoked an angry outcry from survivors in Japan who accused him of trying to justify the use of nuclear weapons against a civilian population. One wonders what Trump’s next move would have been if Iran’s leaders had not joined in a ceasefire after the bunker busting with the enormous, if “conventional,” bombs. The U.S. has “small” nuclear bunker busters as well.

From the English-language Japan Times:

“It seems to me that he does not fully understand the reality of the atomic bombings, which, if used, take the lives of many innocent citizens, regardless of whether they were friend or foe, and threaten the survival of the human race,” Mayor Kazumi Matsui told reporters.

“I wish that President Trump would visit the bombed area to see the reality of the atomic bombing and feel the spirit of Hiroshima, and then make statements,” Kazumi said.

Trump’s comments prompted anger from survivors and a small demonstration in Hiroshima. Last week, the city’s assembly passed a motion condemning remarks that justify the use of atomic bombs.

Atomic bomb survivors’ group Nihon Hidankyo won the Nobel Peace Prize last year, and while accepting the prize, called on countries to abolish the weapons.

NHK on the Nagasaki response:

Suzuki Shiro, the mayor of western Japan’s Nagasaki City, told reporters that the use of nuclear weapons is “unacceptable” under any circumstances, given the tragic and inhumane consequences of the 1945 atomic bombings.

The mayor said he does not understand what Trump meant by the comments, but said that if they were aimed at justifying the atomic bomb attacks, Nagasaki would express its profound regret as one of the affected cities.

Suzuki said that against the backdrop of serious international situations, conveying the realities of the atomic bombings is essential, so that people will understand the inhumanity of nuclear weapons. He invited Trump to the city.

I should note that in my new film we are reminded that after the much-covered visit to Hiroshima by Barack Obama – the first ever by a U.S. president while in office – he did nottravel on to Nagasaki.

I’ve mentioned previously that my new award-winning film with much of its focus on nuclear dangers today will start streaming, and screening on TV, from PBS on July 12. This week the companion e-book with the same title has been published: “The Atomic Bowl: Football at Ground Zero – and Nuclear Peril Today.” It’s just $5.79 and includes previously unpublished stills and material from the film and much more. Read more here. Thanks.

Thanks for reading Oppenheimer and the Legacy of His Bomb ! Subscribe for free to receive new posts and support my work.

https://www.antiwar.com/blog/2025/07/05/hiroshima-and-nagasaki-mayors-criticize-trump-for-hailing-bomb-blasts/

 

 SEE ALSO: https://en.wikipedia.org/wiki/Enola_Gay

 

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