November 25, 1942
Groves selects Los Alamos, NM as the site for a scientific research laboratory, codenamed “Project Y.” J. Robert Oppenheimer is chosen as laboratory director.
December 2, 1942
Fermi’s team at the University of Chicago produces the first sustained nuclear fission chain-reaction with the Chicago Pile-1 (CP-1.)
January 16, 1943
Groves selects Hanford, WA as a site for plutonium production.
February 18, 1943
Y-12 plant construction begins at Oak Ridge.
April 1943
Los Alamos provides its scientists introductory lectures on nuclear physics and bomb design.
June 1943 K-25
gaseous diffusion plant construction begins in Oak Ridge.
August 19, 1943
Roosevelt and Churchill sign the Quebec Agreement.
September 8, 1943
Italy surrenders to Allied forces.
November 1943
Plutonium production begins in the X-10 graphite reactor in Oak Ridge.
February 1944
The Y-12 plant sends 200 grams of uranium-235 to Los Alamos.
June 6, 1944
Allied forces launch the Normandy invasion.
July 17, 1944
Major reorganization to maximize plutonium implosion research occurs at Los Alamos after the plutonium gun-type bomb is abandoned.
July 1944
Scientists at the Chicago Metallurgical Laboratory issue the “Prospectus on Nucleonics,” concerning the international control of atomic energy.
September 1944
Roosevelt and Churchill sign the Hyde Park aide-memoire pledging to continue bilateral research on atomic technology.
September 27, 1944
100-B reactor goes critical, producing plutonium at Hanford shortly after the chain reaction halted due to xenon-135 “poisoning,” which required design modifications.
December 8, 1944
Joseph Rotblat, Polish physicist, resigns from the Manhattan Project upon learning about the abortive German bomb program and that an American atomic bomb will not be used against the Nazis.
February 2, 1945
Los Alamos receives its first plutonium from Hanford.
March 12, 1945
K-25 gaseous diffusion plant begins production in Oak Ridge.
April 12, 1945
Franklin D. Roosevelt dies. Harry S Truman becomes President.
April 25, 1945
Groves and Stimson brief Truman on the Manhattan Project.
April 27, 1945
The Target Committee discusses potential targets in Japan.
May 7, 1945
Nazi Germany surrenders to the Allies.
June 6, 1945
Stimson informs President Truman that the Interim Committee recommends keeping the atomic bomb a secret and using it as soon as possible without warning.
June 1945
The Franck Report, urging demonstration of the bomb before military use, begins circulating among scientists.
June 14, 1945
Groves submits the target selections to General Marshall.
June 21, 1945
The Interim Committee, supporting its Scientific Panel, rejects the Franck Report recommendations.
June 26, 1945
The United Nations charter is signed by delegates of fifty nations.
July 16, 1945
Trinity test, a plutonium implosion bomb and the first nuclear explosion, is successfully conducted in Alamogordo, New Mexico.
July 17,1945
Potsdam conference of Truman, Churchill, and Stalin begins.
July 21, 1945
Truman approves order for the use of atomic bombs.
July 24, 1945
Truman informs Stalin at Potsdam conference that the United States has developed a powerful new weapon.
July 26, 1945
The Potsdam Declaration asks Japan for unconditional surrender and warns of “prompt and utter destruction.”
July 29, 1945
Japan rejects the Potsdam Declaration.
August 6, 1945
The Little Boy uranium bomb is dropped on Hiroshima, Japan.
August 9, 1945
The Fat Man plutonium bomb is dropped on Nagasaki, Japan.
August 12, 1945
Smyth’s Atomic Energy for Military Purposes is released publicly.
August 14, 1945
Japan surrenders.
December 10, 1945
The Bulletin of the Atomic Scientists is first published.
January 24, 1946
The United Nations adopts its first resolution, which establishes the United Nations Atomic Energy Commission.
May 21, 1946
Louis Slotin receives a lethal dose of radiation conducting an experiment at Los Alamos. He dies on May 30.
July 1, 1946
U.S. nuclear weapon testing begins in the Bikini atoll.
August 1, 1946
President Truman signs the Atomic Energy Act establishing the Atomic Energy Commission (AEC) which assumes responsibility for all property in the custody and control of the MED.
January 1, 1947
AEC replaces MED.
August 15, 1947
The Manhattan Engineering District is abolished.
August 29, 1949
USSR conducts its first nuclear test nicknamed Joe-1 at Semipalatinsk test site.
Biographies
[Manhattan Project abbreviated as MP; World War II abbreviated as WWII]
Philip Abelson (1913–2004): American physicist. As a graduate student of Ernest Lawrence at Berkeley in the 1930s, Abelson worked on isolating uranium-235 and created neptunium with Edwin McMillan in 1940. During the MP, Abelson developed the thermal diffusion isotope separation process, which was the method utilized at the S-50 plant at Oak Ridge.
Dean Acheson (1893–1971): American statesman and lawyer. Acheson was known for shaping American foreign policy for the Cold War. He served in the U.S. State Department during the Roosevelt and Truman administrations and was Secretary of State from 1949 to 1952. He played key roles in defining the Truman Doctrine and the Marshall Plan after WWII.
Harold Agnew (1921–2013): American chemist. As a member of Enrico Fermi’s research team at the University of Chicago in 1942, Agnew witnessed the first sustained nuclear chain reaction, Chicago Pile-1. He worked in the Experimental Physics Division at Los Alamos from 1943 to 1945. After the Trinity test, Agnew went to Tinian Island in the Pacific as part of the group responsible for the final bomb assembly. He flew as a scientific observer on the Hiroshima bombing mission. After the war, Agnew went on to serve as director of the Los Alamos National Laboratory from 1970 to 1979.
Luis Alvarez (1911–1988): American physicist. At Los Alamos, Alvarez designed the detonators for the Trinity test bomb and Nagasaki bomb. In addition, he worked on radar and aviation issues during the war and flew as a scientific observer on the Hiroshima mission. Alvarez went on to win the Nobel Prize for Physics in 1968.
Frederick L. Ashworth (1912–2005): United States Navy officer. Ashworth served as the weaponeer on board the Enola Gay when the Fat Man plutonium bomb was dropped on Nagasaki on August 9, 1945. He was later promoted to the rank of Vice Admiral.
Robert Bacher (1905–2004): American physicist. Bacher was a faculty member at Cornell University before he joined the MP in 1943. He was appointed head of the Experimental Physics Division at Los Alamos and later served as head of the Bomb Physics Division.
Kenneth Bainbridge (1904–1996): American physicist. A professor at Harvard, Bainbridge was recruited to work on radar at MIT in 1940. He went to Los Alamos in May 1943 and served as a group leader in the Ordnance Division. Bainbridge was responsible for directing the first test explosion of the atomic bomb, known as the Trinity test, on July 16, 1945.
Hans Bethe (1906–2005): German-born physicist. Bethe fled Nazi Germany in 1933 and accepted a post at Cor
nell University in 1935. He worked at the MIT Radiation Laboratory on radar before joining the MP at Los Alamos in 1943. As head of the Theoretical Physics Division, Bethe was in charge of calculating how the atomic bomb might behave. He was known for his post-war advocacy for arms control and work to publicize the dangers of nuclear weapons. Bethe won the Nobel Prize for Physics in 1967.
Patrick M. S. Blackett (1897–1974): English physicist. Blackett served on the British Maud Committee, a group that was the first to conclude a fission bomb could be made. Though he was involved in early theoretical calculations, he eventually voiced opposition to the development of an atomic bomb. Blackett received the Nobel Prize for Physics in 1948. After WWII he authored several books detailing the consequences of atomic weapons.
Niels Bohr (1885–1962): Danish physicist. Winner of the Nobel Prize for Physics in 1922, Bohr escaped to Sweden during the Nazi occupation of Denmark and later traveled to the U.S. He served as a consultant for the scientists at Los Alamos. Both during and after the MP, Bohr advocated for peaceful applications of atomic energy and openness between nations with regard to nuclear weapons.
Vannevar Bush (1890–1974): American engineer and science administrator. In 1940 the National Defense Research Committee was established and President Roosevelt appointed Bush as its president. A year later the Office of Scientific Research and Development was created, absorbing the NDRC, with Bush as director. He was at the center of efforts to have the U.S. government develop an atomic bomb, which led to the formation of the Manhattan Project in June 1942. Bush served on the Military Policy Committee, was actively involved in recruiting scientists, and advised Secretary of War Henry Stimson and others on the future international implications of the atomic bomb.
Sir James Chadwick (1891–1974): Cambridge physicist. Chadwick discovered the neutron in 1932, for which he received the Nobel Prize for Physics in 1935. Following the Frisch-Peierls memorandum in 1940, he supervised the experimental work on the properties of uranium in England and was the author of the Maud Report (1941). After the Quebec Agreement was signed, he led the British scientific mission to Los Alamos, and later transferred to Washington where he worked with General Groves. In August 1945 he predicted that the American nuclear monopoly would not last more than a few years and was instrumental in setting up Britain’s independent atomic weapons program.
Winston Churchill (1874–1965): Prime Minister of Great Britain from 1940 to 1945 and 1951 to 1955. In 1940, after the Maud Committee determined the feasibility of an atomic bomb, the British government launched the Tube Alloys project to research nuclear weapons development. The British work spurred Americans to invest in the MP. In 1943, Churchill and Franklin Roosevelt negotiated the Quebec Agreement, in which Britain and the U.S. agreed to share resources and information. As a result, some 90 scientists, known as the British Scientific Mission, worked at various MP sites, with two dozen of them at Los Alamos.
Arthur H. Compton (1892–1962): American physicist. A professor at the University of Chicago, Compton earned the Nobel Prize for Physics in 1927. In 1941 he headed a National Academy of Sciences committee that examined the potential use of atomic energy for military purposes, work that was already going on at Chicago. From 1942 to 1945, Compton was director of the Metallurgical Laboratory, an important university outpost of Manhattan Project research and development where the first controlled chain reaction took place. The Met Lab supported the development, construction, and operation of the reactors at Hanford and the enrichment activities at Oak Ridge.
James B. Conant (1893–1978): American chemist and government official. Conant served as president of Harvard from 1933–1953. He worked closely with Vannevar Bush to spur the U.S. government to develop an atomic bomb, serving as Chairman of the National Defense Research Committee to mobilize science for the war effort. He was Bush’s alternate on the Military Policy Committee and served as one of General Groves’s advisers on scientific matters. He witnessed the Trinity test and was on the Interim Committee that made recommendations on using the atomic bombs against Japan.
Albert Einstein (1879–1955): German-born physicist who personifies twentieth-century science. In 1905 he published the concept that energy and mass are equivalent, famously expressed E=mc2. His work sought to explain the “relativity” of natural forces. Einstein immigrated to the U.S. in 1933, and in 1939 signed a letter to President Franklin Roosevelt warning of German nuclear weapons research. He played no role in the Manhattan Project and after World War II worked to control nuclear proliferation.
Dwight D. Eisenhower (1890–1969): President of the United States from 1953 to 1961. A top general during World War II, Eisenhower had no involvement with the Manhattan Project. However, as President, he initiated the Atoms for Peace program in 1953, which encouraged international focus on peaceful uses of atomic energy and distributed nuclear materials and technology to countries with less advanced research programs. He also oversaw an enormous buildup of U.S. nuclear weapons, from 1,500 in 1953 to over 20,000 in 1961.
Thomas Farrell (1891–1967): United States Army officer. In early 1945, Farrell was named Deputy Commanding General for the Manhattan Engineer District, serving as second-in-command to General Leslie Groves. He was first stationed at Los Alamos, where he supervised the Trinity test. Subsequently, Farrell coordinated preparations on Tinian Island for the Hiroshima and Nagasaki bombing missions. In September 1945, he led two teams of scientists and officers to Hiroshima and Nagasaki to examine the damage caused by the atomic bombs.
Enrico Fermi (1901–1954): Italian-born physicist. Fermi won the Nobel Prize for Physics in 1938 and used his trip to accept the prize in Sweden as an opportunity to immigrate to the U.S. in order to escape anti-Semitism in Fascist Italy. Initially a professor at Columbia, he moved to the University of Chicago at the beginning of the MP and along with Leo Szilard, co-designed the first nuclear reactor, Chicago Pile-1 (CP-1). Fermi’s team was the first to achieve a sustained chain reaction when CP-1 went critical on December 2, 1942. He was also present in the control room when the first reactor at Hanford, the B reactor, went critical in 1944. Fermi went to Los Alamos as an Associate Director and key consultant in August 1944.
Richard Feynman (1918–1988): American physicist. Feynman joined the MP following his doctoral work at Princeton University. At Los Alamos, he was a group leader in the Theoretical Physics Division and was present for the Trinity test. Feynman was known for playfully challenging excessive security at Los Alamos, cracking safes and sending coded messages to his hospitalized wife. He received the Nobel Prize for Physics in 1965.
Val Fitch (1923–2015): American physicist. Fitch was a member of the Special Engineer Detachment at Los Alamos and worked in the Experimental Physics Division. After the war, he joined the faculty at Princeton and won the Nobel Prize for Physics in 1980.
James Franck (1882–1964): German-born physicist. Franck won the Nobel Prize for Physics in 1925. He left Germany after Hitler’s regime began persecuting Jews in academic positions and immigrated to the U.S. in 1935, where he held professorships at Johns Hopkins and the University of Chicago. During the MP, Franck served as director of the chemistry division at the University of Chicago Metallurgical Laboratory. In May 1945, he headed a committee to explore a number of issues related to atomic energy policy. The committee issued a report in June 1945 advocating a public demonstration of the atomic bomb.
Otto Frisch (1904–1979): Austrian-born physicist. Frisch moved from Germany to Britain in 1933 when Hitler came to power. With his aunt, Lise Meitner, he explained the physics behind Otto Hahn’s observed splitting of a uranium nucleus, which Meitner and Frisch dubbed “fission.” In 1940, Frisch and Rudolf Peierls designed the first theoretical detonator for a fission bomb and pointed out that a relatively small critical mass of uranium-235 was necessary for a feasible bomb. The Frisch-Peierls memorandum became the basis for the British atomic bomb project. Frisch joined the MP at Los Alamos in 1943.
Klaus Fuchs (1911–198
8): German-born physicist and atomic spy for the Soviet Union. After emigrating from Germany to Britain, Fuchs went to Los Alamos in 1944 as part of the British Mission, a group of scientists sent to aid the American atomic bomb effort. At Los Alamos, he was responsible for a number of important theoretical calculations. However, in early 1950, Fuchs was convicted of sharing information about the atomic bomb effort with the Soviet Union during and after WWII. He was released from prison after serving nine years and lived the rest of his life in East Germany.
Crawford H. Greenewalt (1902–1993): American chemical engineer. During the MP, Greenewalt worked for the DuPont Company as a liaison with the scientists at the University of Chicago and technical director for the Hanford plutonium production plants. After the war, he served as president of DuPont from 1948 to 1967.
David Greenglass (1922–2014): Atomic spy for the Soviet Union. Greenglass joined the Army in 1943. He was first stationed at Oak Ridge and later sent to Los Alamos. In November 1944, after his brother-in-law Julius Rosenberg told Greenglass’s wife that the MP was an effort to develop an atomic bomb, Greenglass began to pass nuclear secrets to the Soviet Union. His espionage was uncovered in 1950 and he served ten years in prison. Greenglass also implicated Julius and Ethel Rosenberg, who were executed in 1953 for conspiracy to commit espionage.
Leslie R. Groves (1896–1970): United States Army officer. A graduate of West Point, Groves entered the Army Corps of Engineers in 1918 and was promoted several times before being named deputy to the Chief of Construction in 1940. For the next two years Groves basically oversaw all Army domestic construction projects, including the Pentagon. In September 1942, he was appointed to head the MP.
The Manhattan Project Page 51