The Secret Letters of the Manhattan and Groves Project

The Manhattan Project was a secret military project created in 1942 to produce the first US nuclear weapon. Fears that Nazi Germany would build and use a nuclear weapon during World War II triggered the start of the Manhattan Project, which was originally based in Manhattan, New York.

US physicist Robert Oppenheimer and General Leslie R. Groves served as directors of this project, which recruited some of the best US scientists, engineers and mathematicians. A number of European scientists, including Albert Einstein, Enrico Fermi, and Leo Szilard, also participated in the Manhattan Project.

Under the auspices of the Manhattan Project, three main research and production facilities were established at Oak Ridge, Tennessee; at Hanford, Washington; and at Los Alamos, New Mexico. The Oak Ridge Laboratories provided uranium-235 and Hanford produced weapons-grade plutonium. The Los Alamos Laboratory became the site for assembling nuclear weapons.

Los Alamos produced four weapons, two of which, Little Boy and Fat Man, were used against Japan in August 1945. The Manhattan Project officially ended in 1946 when it became part of the Atomic Energy Commission (AEC).

How this Project came to be?

Albert Einstein wrote a letter to Franklin Delano Roosevelt proposing a “project” which will harness nuclear energy as powerful weapon that can be used to defend the interests of the United States of America. This letter was delivered to President Roosevelt on October 11, 1939, and ten days later the first meeting of the Advisory Committee on Uranium (Briggs Uranium Committee) was held in Washington, DC on President Roosevelt’s order.

Letter Proposal of Einstein to FDR dated August 2, 1939:

Old Grove Rd.
Nassau Point
Peconic, Long Island

August 2nd, 1939

F.D. Roosevelt
President of the United States
White House
Washington, D.C.


Some recent work by E. Fermi and L. Szilard, which has been communicated to me in manuscript, leads me to expect that the element uranium may be turned into a new and important source of energy in the immediate future. Certain aspects of the situation which has arisen seem to call for watchfulness and, if necessary, quick action on the part of the administration. I believe therefore that it is my duty to bring to your attention the following facts and recommendations:

In the course of the last four months it has been made probable — through the work of Joliot in France as well as Fermi and Szilard in America — that it may become possible to set up a nuclear chain reaction in a large mass of uranium, by which vast amounts of power and large quantities of new radium like elements would be generated. Now it appears almost certain that this could be achieved in the immediate future.

This new phenomenon would also lead to the construction of bombs, and it is conceivable — though much less certain — that extremely powerful bombs of a new type may thus be constructed. A single bomb of this type, carried by boat and exploded in a port, might very well destroy the whole port together with some of the surrounding territory. However, such bombs might very well prove to be too heavy for transportation by air.

The United States has only very poor [illegible] of uranium in moderate quantities. There is some good ore in Canada and the former Czechoslovakia, while the most important source of Uranium is Belgian Congo.

In view of this situation you may think it desirable to have some permanent contact maintained between the Administration and the group of physicists working on chain reactions in America. One possible way of achieving this might be for you to entrust with this task a person who has your confidence and who could perhaps serve in an unofficial capacity. His task might comprise the following:

a) To approach Government Departments, keep them informed of the further development, and out forward recommendations for Government action, giving particular attention to the problem of uranium ore for the United States;

b) To speed up the experimental work, which is at present being carried on within the limits of the budgets of University laboratories, by providing funds, if such funds be required, through his contacts with private persons who are willing to make a contribution for this cause, and perhaps also by obtaining the co-operation of industrial laboratories which have the necessary equipment.

I understand that Germany has actually stopped the sale of uranium from the Czechoslovakian mines, which she has taken over. That she should have taken such early action might perhaps be understood on the ground that the son of the German Under-Secretary of State, Von Weishlicker [sic], is attached to the Kaiser Wilheim Institute in Berlin where some of the American work on uranium is now being repeated.

Yours very truly,

(Albert Einstein)


Here is another letter of Albert Einstein to President FDR:

March 25, 1945


The Honorable Franklin Delano Roosevelt

The President of the United States

The White House

Washington, D.C.


I am writing you to introduce Dr. L. Szilard who proposes to submit to you certain considerations and recommendations. Unusual circumstances which I shall describe further below induce me to take this action in spite of the fact that I do not know the substance of the considerations and recommendations which Dr. Szilard proposes to submit to you.

In the summer of 1939 Dr. Szilard put before me his views concerning the potential importance of uranium for national defense. He was greatly disturbed by the potentialities involved and anxious that the United States Government be advised of them as soon as possible. Dr. Szilard, who is one of the discoverers of the neutron emission of uranium on which all present work on uranium is based, described to me a specific system which he thought would make it possible to set up a chain reaction in un-separated uranium in the immediate future. Having known him for over twenty years both from his scientific work and personally, I have much confidence in his judgment as well as my own that I took the liberty to approach you in connection with this subject. You responded to my letter dated August 2, 1939 by the appointment of a committee under the chairmanship of Dr. Briggs and thus started the Government’s activity in this field.

The terms of secrecy under which Dr. Szilard is working at present do not permit him to give me information about his work; however, I understand that he now is greatly concerned about the lack of adequate contact between scientists who are doing this work and those members of your Cabinet who are responsible for formulating policy. In the circumstances I consider it my duty to give Dr. Szilard this introduction and I wish to express the hope that you will be able to give his presentation of the case your personal attention.

Very truly yours,

Albert Einstein


Further developments were done in 30 secret sites across the United States, Canada and the United Kingdom as well as simultaneous conferences were done regarding the Manhattan Project. Some of these were The Quebec Agreement (August 19, 1943), The Anglo-American Declaration of Trust (June 13, 1944) and the Roosevelt-Churchill “Tube-Alloys Deal (September 19, 1944).

On April 12, 1945, President Franklin Delano Roosevelt died at 3:35pm in Little White House at Warm Springs, Georgia. FDR never saw the results of the secret project he had started in 1939. He was succeeded by his Vice-President, Harry S. Truman on the same day.


The Truman Administration

When Truman became president on April 12, 1945, upon the death of President Roosevelt, he had no knowledge of the actual bomb project itself and his first information about what was really being done came from Secretary of War Henry L. Stimson on April 25th.

Stimson himself was virtual head of the project and had been during the years of its development as a military weapon. Stimson had conferred frequently with President Roosevelt during this period but his last meeting with FDR had been on March 15th.

Copy of the April 24, 1945 letter of Secretary Stimson to President Truman regarding the Manhattan Project (declassified on April 12, 1974)

April 24, 1945

Dear Mr. President:

I think it is very important that I should have a talk with you as soon as possible on a highly secret matter.

I mentioned it to you shortly after you took office but have not urged it since on account of the pressure you have been under. It, however, has such a bearing on our present foreign relations and has such an important effect upon all my thinking in this field that I think you ought to know about it without much further delay

Faithfully yours,

Henry L. Stimson


After this revelation of Secretary of War Henry L. Stimson, Truman set-up a secret committee composed of Military Generals, Cabinet Secretaries and Scientists to further discuss the development of the Atomic Bomb and other information regarding the Pacific War. The meetings lasted from April to July 1945 until the fateful day of dropping the Atomic Bomb on August 7 and 9 of 1945.

The Trinity Nuclear Test was the code name of the detonation of the first nuclear device. The Oppenheimer Group was able to produce 4 bombs including the Little Boy and Fat Man. This test was conducted by the United States Army on July 16, 1945, in the Jornada del Muerto desert about 35 miles southeast of Socorro, New Mexico, at the new White Sands Proving Ground, which incorporated the Alamogordo Bombing and Gunnery Range. Details of this activity were sent through a report by Leslie R. Groves to Henry Stimson on July 18, 1945. This is a 14-page file declassified in 1974.

Here is the link of the full 14-page report:


The Groves Project

After the Trinity Nuclear Test, the United States Government began the assembly of the Nuclear Atom Bomb in the US Air Base in Tinian Islands in the Pacific. The materials were delivered by the USS Indianapolis, a Portland-Class Cruiser of the US Navy. The delivery of these materials lasted for 3 days. On July 30, 1945, the USS Indianapolis was set to go back to the US Naval Base in America but a tragedy happened. The ship was torpedoed on its way home, 300 were killed immediately by the explosion and 900 were killed by shark infestation.

There were reports that the Japanese torpedoed the ship but there were also reports that the sinking of the ship was ordered by the US Government. According to reports, “The Groves Project was so secret in nature that the US Government ordered to sink the USS Indianapolis after its delivery of Nuclear materials in Tinian Islands.” The rest of the world did not know yet of this powerful weapon and that the United States cannot risk the possibility of leakage of this project which will be very detrimental to US national security. (The Groves Project is the final plan for launching the Atomic Bomb)

Here is the Final Memorandum of the Groves Project before the launching of the Nuclear Bomb:

(Letter of John Stone to General Arnold dated July 24, 1945)

24 July 1945


Subject: Groves Project

1. The following plan and schedule for initial attacks using special bombs have been worked out:

a. The first atom bomb (gun type) will be ready to drop between August 1 and 10 and plans are to drop it the first day of good weather following readiness.

b. The following targets have been selected: Hiroshima, Kokura, Niigata and Nagasaki.

(1) Hiroshima (population 350,000) is an “Army” city; a major POE; has large QM and supply depots; has considerable industry and several small shipyards.

(2) Nagasaki (population 210,000) is a major shipping and industrial center of Kyushu.

(3) Kokura (population 178,000) has one of the largest army arsenals and ordnance works; has the largest railroad shops on Kyushu; and has large munitions storage to the south.

(4) Niigata (population 150,000) is an important industrial city, building machine tools, diesel engines, etc., and is key port for shipping to the mainland.

c. All four cities are believed to contain large numbers of key Japanese industrialists and political figures who have sought refuge from major destroyed cities.

d. The attack is planned to be visual to insure accuracy and will await favorable weather. The four targets give a very high probability of one being open even if the weather varies from that forecast, as they are considerably separated.

e. The bomb will be carried in a master airplane to be accompanied by two other project B-29’s with observers and special instruments.

f. The three B-29’s will take off from North Field, Tinian, and fly via Iwo Jima. The use of fighter escort will be determined by General Spaatz upon consideration of all operational factors.

g. The master plane will attack the selected target from 30,000 feet plus altitude and will immediately upon release of the bomb make a steep diving turn away from the target to achieve maximum slant range distance as quickly as possible. Recording planes and fighters if employed will be kept several miles from the target. The participating planes are believed to be safe from the effects of the bomb.

h. The bomb will be detonated by radar proximity fuse about 2000 feet above the ground.

i. Emergency arrangements have been provided at Iwo Jima for handling the bomb if required.

2. Two tested type bombs are expected to be available in August, one about the 6th and another on the 24th. General Groves expects to have more information on future availabilities in a few days which will be furnished you when received.

3. The above has been discussed with Generals Spaatz and Eaker who concur.

John Stone

Colonel, USC


The Memorandum sent to General Carl Spaatz to bomb Japan (just waiting for confirmation from President Truman):

25 July 1945

TO: General Carl Spaatz

Commanding General

United States Army Strategic Air Forces

1. The 509 Composite Group, 20th Air Force will deliver its first special bomb as soon as weather will permit visual bombing after about 3 August 1945 on one of the targets: Hiroshima, Kokura, Niigata and Nagasaki. To carry military and civilian scientific personnel from the War Department to observe and record the effects of the explosion of the bomb, additional aircraft will accompany the airplane carrying the bomb. The observing planes will stay several miles distant from the point of impact of the bomb.

2. Additional bombs will be delivered on the above targets as soon as made ready by the project staff. Further instructions will be issued concerning targets other than those listed above.

3. Discussion of any and all information concerning the use of the weapon against Japan is reserved to the Secretary of War and the President of the United States. No communiques on the subject or releases of information will be issued by Commanders in the field without specific prior authority. Any news stories will be sent to the War Department for specific clearance.

4. The foregoing directive is issued to you by direction and with the approval of the Secretary of War and of the Chief of Staff, USA. It is desired that you personally deliver one copy of this directive to General MacArthur and one copy to Admiral Nimitz for their information.


General, G.S.C.

Acting Chief of Staff


Secretary of War Henry L. Stimson feeling the urgency of launching the Atomic Bombs as soon as possible to end the horrors of war brought by World War II wrote a letter to President Truman reiterating the position of the United States.

Here is a copy of the letter of Secretary Stimson to President Truman:

FROM: AGWAR Washington

TO: Tripartite Conference Babelsburg, Germany

NO: WAR 41011

30 July 1945

To the President from the Secretary of War.

The time schedule on Grove’s project is progressing so rapidly that it is now essential that statement for release by you be available not later than Wednesday, 1 August. I have revised draft of statement, which I previously presented to you in light of

(A) Your recent ultimatum,

(B) Dramatic results of test and

(C) Certain minor suggestions made by British of which Byrnes is aware.

While I am planning to start a copy by special courier tomorrow in the hope you can be reached, nevertheless in the event he does not reach you in time, I will appreciate having your authority to have White House release revised statement as soon as necessary.

Sorry circumstances seem to require this emergency action.

ACTION: Gen. Vaughar

VICTORY-IN-733                                                                                                  (31 July 1945)


President Truman on July 31, 1945 officially approved the launching of the Atomic Bomb to Japan.

Here is the handwritten note of President Truman at the back of the letter of Secretary Stimson:

Sec War

Reply to your 41011 suggestions approved. Release when ready but not sooner than August 2.



The first atomic bomb nicknamed “Little Boy” was dropped at the targeted city of Hiroshima on August 6, 1945. It was released by the Boeing B-29 Superfortress bomber named “Enola Gay” and piloted by Colonel Paul Tibbets.

The second atomic bomb nicknamed “Fat Man” was dropped at the targeted city of Nagasaki on August 9, 1945. The plane that was supposedly to be used was “The Great Artiste”, a Silverplate B-29 bomber. The plane that was used was Bockscar, also a Silverplate B-29 bomber, because the instrumentation was not yet removed from the Great Artiste. To avoid delays, the latter was used. It was piloted by Major Charles Sweeney.

Of the four possible cities to be bombed namely Hiroshima, Nagasaki, Kokura and Niigata; Hiroshima and Nagasaki were chosen as the bombing sites since weather on these places during that time were very fine that launching of Atomic Bombs were highly possible. The US cannot afford weather disturbances that could alter the radar target of the B-29 Bombers.

After the launch of the two Atomic Bombs, negotiations and invasions of the Allied forces in the Pacific began. There were several events happened after the bombings that led to VJ Day or Victory in Japan Day. Japan surrendered on September 2, 1945 and the rest, as they say, is history.



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