Atomic Bomb - Chronology

1930-1941

1942-1944

1945-1946

Atomic Bomb Chronology: 1930-1941                                                                              top

1930. 3 [U.S.A.] Pluto discovered by C.W.Tombaugh. (see plutonium)
1930 [Germany] Discovery of radiation which penetrates a leadblock by Walter Bethe. (Received 1954 Nobel prize.)
1932. 1.18 [France] Proton emission from beryllium irradiated by alpha-ray, discovered by Frederick Joliot and Irene Curie.
1932. 2.27 [England] Neutron discovered by James Chadwick, verifying Rutherford's Baker Lecture. (Received 1935 Nobel prize.)
1932. 2 [U.S.A.] Cyclotron developed by Ernest Orlando Lawrence and M.S.Livingston of California University, 27.5 inch size developing one million electron volts. (Received 1939 Nobel prize)
1932. 4 [England] Conversion of element by John Douglas Cockcroftand Ernest Thomas Sinton Walton. Emergence of helium by irradiating highspeed proton to lithium, based on Gamow's tunnel effect. (Received 1951Nobel prize)
1932. 8. 2 [U.S.A.] Positron discovered by Carl David Anderson, detecting a cosmic-ray shower using a cloud chamber. (Received 1936 Nobel prize)
1932 [U.S.A.] Deuterium discovered by Harold Clayton Urey. (Received1934 Nobel prize)
1932.12 Albert Einstein seeks refuge in Belgium.
1933. 1.30 [Germany] Adolf Hitler becomes the Fuehrer of the Third Reich.
1933. 3.30 Leo Szilard escapes from Berlin to Vienna.
1933. 4. 7 [Germany] Promulgation of anti-Judish law by Nazi government.
1933.5 L. Szilard moves to England.
1933. 9. 9 A. Einstein moves to England.
1933. 9.12 [England] Idea of chain reaction via neutron by L.Szilard.He took a hint on the Times' report of Rutherford's lecture about atomic transition. The idea of atomic bomb was patented in 1934. The patent was transferred in secret to England's navy, 1936.2.
1933.10. 7 Albert Einstein moves to U.S.A.
1933.10 The 7th Solvay meeting. M. Curie, E. Rutherford, N. Bohr,L. Meitner, W. Heisenberg, W. Pauli, E. Fermi, J. Chadwick, G. Gamow, F.and I. Curie, P.M.S. Blackett, R.E. Peierls. In Brussels. On the structure of proton.
1933.10 G. Gamow escapes from Soviet Union, seeks refuge in U.S.A. after the Solvay meeting.
1933.12 [Italy] Weak interaction and beta-decay theory by Enrico Fermi. (Received 1938 Nobel prize.)
1933 Rudolf Ernst Peierls seeks refuge in England.
1933 [Germany] Project of rocket development; by v.Brown.
1934. 1.15 [France] Artificial radioactivity. F. and I. Curie detected radioactive phosphorus and positron by means of a Geiger counter after irradiating aluminum with alpha-rays from polonium. Blessed by M.Curie who was suffering from leucaemia caused by irradiation. (Recieved 1935Nobel prize)
1934. 5.10 [Italy] Transuranic elements assumed by E.Fermi based on experimental results of irradiation of proton from radon and beryllium to uranium
1934. 9 [Germany] Possibility of nuclear fission proposed by Ida Noddack, a feminine scientist, not attracting attention.
1934.10.22 [Italy] Radioactivity induced by slow neutrons discovered by E.Fermi.
1934 [United Kingdom] Hydrogen fusion reaction discovered by Marcus Oliphant and Paul Harteck, Cavendish Laboratory. Bombarding hydrogen2-deutreum, in the form of concentrated heavy water- with deuterium-accelerated nuclei.
1934 [U.S.S.R.] A small cyclotron was built by Abram I. Alikhanov and Igor Kurchatov. The first cyclotron operating outside U.S.A.
1935. 2 Hans Albrecht Bethe seeks refuge in U.S.A.
1935. 8 Edward Teller seeks refuge in U.S.A.
1935 Eugene Paul Wigner and Johann Ludwig von Neumann seek refuge in U.S.A.
1935 [Japan] Meson predicted by Hideki Yukawa. Pi meson is a hadron involved in alpha-decay and nuclear force. (Received 1949 Nobel prize.)
1936. 1.27 [Denmark] Liquid-drop model of atomic nucleus proposed by Niels Bohr.
1936 [England] Energy production by conversion of hydrogen to helium proposed in a lecture by Francis William Aston.
E=mc2. A glass of water is enough for a full speed cruise of the Queen Mary in Atlantic Ocean.
1937. 4.26 [Germany][SPAIN] Guernica. Indiscriminate bombing by German air force assisting Franco army. Protested by P. Picasso in famous painting.
1937 [U.S.A.] Cyclotron with 60 inches diameter and 220 tons magnet; Planed by E.Lawrence as a medical appliance, depending on private contribution.
1938. 3.13 [Germany] Austria annexed.
1938. 7.14 [Italy] Jews banned from public office.
1938. 7.17 L.Meitner with a help by N.Bohr escapes carrying an expired passport from Germany to Stockholm via Copenhagen.
1938. 8 Emilio Gino Segre seeks refuge in U.S.A.
1938. 9 [France] Radioactivity with a half life of 3.5 hr produced by neutron irradiation of uranium is from lanthanum, reported by Curie and Savitch.
1938 [U.S.A.] Uranium 235 and uranium238(ratio of 1:139 in natural uranium), analyzed by Alfred Nier by means of Dempster's mass spectrometer.
1938 [Germany] Isotope-separating device developed by Klaus Cladius and G.Dicker employing a gas thermal diffusion method.
1938.12.19 [Germany] Uranium nuclear fission: Barium is detected by Otto Hahn and Fritz Strassmann after irradiation by neutron of uranium at Kaiser Wilhelm Institute. They asked L.Meitner's comments by a letter. Beginning of the Barium Fantasy. (Received 1944 Nobel prize.)
1939. 1. 2 E.Fermi travels to U.S.A. Awarded Nobel prize and seeks refuge in U.S.A with a help of N. Bohr. Fermi's wife is a Jew.
1939. 1. 6 [Denmark] A theoretical explanation of nuclear fission of uranium written by L.Meitner and Otto Frisch employing a liquid drop model and theory of relativity. Next day N.Bohr brought a copy of the paper to U.S.A. Conversion of one fifth of the mass of a proton to energy is plausible.
1939. 1.13 [Denmark] Detection of uranium nuclear fission by a cloud chamber by Otto Frisch. Later nuclear fission of thorium was verified. Thorium nuclear fission is triggered with fast neutron.
1939. 1.14 [Denmark] Nuclear Fission named by Otto Frisch, an analogy of bacterial cell division called binary fission, suggested by William Arnold, an American Biologist.
1939. 1.16 [U.S.A.] N.Bohr travels to New York.
Bohr did not wish to make the nuclear fission story public, but John Feurer announced the news at a meeting at Princeton University.
1939. 1.17 [Denmark] Otto Frisch submits a paper of the theory and experiments on nuclear fission of uranium.
1939. 1.25 [U.S.A.] Verification of the uranium nuclear fission by means of an oscilloscope by Herbert Anderson, a student of Fermi. Emission of neutron by irradiating hydrogen with deuteron accelerated by means of cyclotron at Columbia University. Failure in previous experiment by Fermi in Rome was due to an obstruction by aluminum foils.
1939. 1.26 [France] Verification of uranium nuclear fission by J. and I. Curie. They failed to detect neutron emission.
1939. 1.26 [U.S.A.] The fifth Washington meeting sponsored by American Physics Society. N. Bohr, E. Fermi, Otto Stern, H.C. Urey, Gregory Bright, Issidor Isaac Rabi, G. Gamow, E. Teller, Merle Tuve. Lectures by N.Bohrand E.Fermi on the uranium nuclear fission called "splitters."
1939. 1.28 [U.S.A.] Verification of uranium nuclear fission by Richard Roberts and Robert Meyer. Emission of neutron on irradiating lithium with deutron accelerated by a van de Graaff accelerator, was employed for irradiation of uranium. Demonstration to members in the Washington Conference. Delayed neutron was detected in later experiments, a discovery suggesting a possibility of reactor control.
1939. 1.30 [U.S.A.] Verification of uranium nuclear fission by Phillip Abelson. Luis Walter Alvarez transferred the news of nuclear fission of uranium to Abelson. They found tellurium-52 and zirconium-40 as the fission products. J.R.Oppenheimer, as noted by Alvarez, predicted neutron emission and possibility of developing atomic bomb.
1939. 2.7 [U.S.A.] Nuclear fission of 235uranium is caused by slow neutron, a theory proposed by N.Bohr and John Archibald Wheeler.
1939. 3.17 [U.S.A.] The first meeting on nuclear energy for military purposes. The first proposal by scientists (G.P. Pegram and E.Fermi) of the development of atomic bomb to Navy. E. Fermi talked on the controlled reaction by slow neutron, explosion by fast neutron and reaction in the supernova.
1939. 3 [France] More than one neutron emitted with nuclear fission of uranium observed by J. Curie, Hans Halban and Lew Kowarski.
1939. 3 [U.S.A.] About two neutrons emitted with nuclear fission of uranium verified independently by L.Szilard and Walter Zinn.
1939. 4.22 [France] Number of neutrons emitted with nuclear fission of 235uranium is 3.5 /fission. Later corrected to 2.6/fission.By F.J.Curie, H.Halban and L.Kowarski.
1939. 4.29 [Germany] A secret conference about a research program on the nuclear bomb in Berlin. A trade embargo on uranium and radium. Letter of Paul Harteck.
1939. 4 [U.S.A.] John Dunning's request to Alfred Nier to separate235uranium.
1939. 5 N. Bohr returns to Copenhagen in order to support refugee scientists.
1939. 7.3 [U.S.A.] Idea of nuclear reactor (pile) by E.Fermi and L.Szilard.Natural uranium as fuel and graphite as moderator of neutron energy.
1939. 8. 2 [U.S.A.] A letter of A.Einstein to President Roosevelt.L. Szilard, E. Teller and E. Wigner persuaded Einstein to warn President Roosevelt of German menace. The letter suggested the possibility of uranium bomb.
1939 Otto Frisch seeks refuge in England.
1939. 9. 1 World War II begins with the German invasion of Poland. Blitzkrieg by tanks.
1939. 9. 3 England and France go to war against Germany.
1939. 9.16 [Germany] A secret conference in Berlin on Bohr's paper about nuclear fission.
1939. 9.26 [Germany] The second Berlin meeting. Start of German nuclear bomb project: Kurt Diepner, Erich Bagge , W. Heisenberg and Paul Harteck.
1939.10.11 [U.S.A.] Einstein's letter to President Roosevelt, presented by Alexander Sachs.
1939.10.21 [U.S.A.] The 1st uranium advisory committee. Financial aid to development of nuclear reactor rather than to yet uncertain atomic bomb.[A. Lyman, J. Briggs, A. Sachs, L. Szilard, E. Teller and E. Wigner]
1939.10 [England] An idea by J. Chadwick for an atomic bomb utilizing natural uranium based on a paper by R.Peierls, mass needed for critical state: 30-40 tons.
1939.12.6 [Germany]Report by W.Heisenberg of the possibility of a uranium bomb to Germany Department of War.
1939.12 [U.S.A.] A discovery by Edwin Mattison McMillan of the existence of the radioactive substance that stays in uranium on nuclear fission experiment.
1939 [U.S.A.] A theory of energy production in stars by Hans Albrecht Bethe, the carbon cycle. (Received 1967 Nobel Prize.)
1940.2.1 [England] An idea by O.Frisch and E.Peierls of highly enriched uranium bomb presented in a 3 page memo describing the critical mass as 600 g. Presented via Mark Oliphant of Birmingham University to Henry T. Tizard.
1940.2.29 [U.S.A.] Separation of uranium235 by A.Nier. 1/1,000,000,000gon a nickel film was sent to John R.Dunning in a letter. Uranium chloride(IV)or uranium fluoride(IV) was used. Minnesota University.
1940.2 [U.S.A.] Uranium research budget of $6000 authorized: the purchase cost of graphite for E.Fermi and L.Szilard.
1940.3.2 [U.S.A.] Verification of uranium235 fission with slow neutron by J.Dunning (irradiation by a cyclotron of a sample separated by A.Nier. (Colombia University)
1940.4.9 [Germany] Invasion and occupation of Denmark.
1940.4.10 [England] George Paget Thomson committee. Small scale separation experiments utilizing uranium fluoride(VI) agreed.
1940.4.24 [England] The 2nd George Paget Thomson committee.
1940.4.28 [U.S.A.] The 2nd uranium advisory committee. Necessity of basic research admitted. George B. Pegram and E. Fermi sit in.
1940.5.10 [U.S.A.] President Roosevelt's appeal for cooperation of The American Scientists Federation. E. Teller decides to participate in nuclear weapon research.
1940.5.27 [U.S.A.] A new 93rd element is discovered through irradiation of uranium oxide using deutrons accelerated by a cyclotron. Called Neptuniumby E.McMillan. (Received 1951 Nobel Prize)
1940.5.27 [U.S.A.] The possibility of nuclear fission of transuranic elements proposed by Louis A. Turner.
1940.6 [France] H. Halban and L. Kowarski escape to England carrying180 L heavy water with all the data of J.Curie. An test of a chain reaction utilizing the heavy water carried out at the Cavendish Laboratory failed.
1940.6.14 [France] Paris falls to the German army.
1940.6 [U.S.A.] National Defense Research Committee(NDRC) swallows up uranium advisory committee. Project for enriching 235uranium and elimination of refugee scientists discussed.
1940.6 [England] A gas dispersion method experiment by Franz Simon, utilizing a copper partition for separating vapor and carbon dioxide.
1940.6 [England] Renaming of George Paget Thomson committee to MAUD committee.
1940.6 [Soviet Union] Uranium Committee established in Academy of Science by Igor Kurchatov. Interrupted due to German invasion in June,1941.
1940.10 [Japan] Army commander Suzuki's report of the possibility of developing an atomic bomb based on a survey of uranium deposit in Chinese and Burma.
1940.11 [U.S.A.] E. McMillan moves to radar research at MIT.
1940.11 [U.S.A.] Start of experiment on gas dispersion method for enriching uranium-235 by H.Urey and J.Dunning. Uranium fluoride(VI) vaporizes at 56 deg C.
1940.12.15 [U.S.A.] Nuclear fission of the new element 94239foreseen by E.Fermi and E. Segre. The possibility of a new element produced in a nuclear reactor.
1940.12.16 [U.S.A.] A new element 94239. A plan for production utilizing the 60-inchs cyclotron proposed by E. Lawrence, E. Segre, E.Fermi and G. Pegram.
1940.12.28 [England] A new idea of heavy water nuclear reactor by H.Halban. A method for separation of element 93, discovered by Pletcher was conveyed to U.S.A.
1940.12 [England] A plan for a factory for separation of uranium235by F.Simon. (MAUD committee, gas dispersion method.)
1940.12 [England] A possibility of nuclear fission of new element94 reported to MAUD committee.
1940.12 [Japan] A measurement of cross-section started by Yoshio Nishina. Blueprint of 60-inch cyclotron was a gift of E. Lawrence.
1940 [Soviet Union] Spontaneous fission of uranium discovered by George Flerov.
1941 [U.S.A.] P.Abelson moves to Navy Research Institute in order to develop a small size nuclear reactor for submarine.
1941.1.28 [U.S.A.]A new element 94238discovered by E.Segreand Glenn T. Seaborg. Uranium oxide was irradiated by deutrons accelerated with a cyclotron. (Received 1951 Nobel prize.)
1941.2.23 [U.S.A.] New element 94 chemically separated as a solution by E. Segre, G. Seaborg and Arthur Wall.
1941.3.6 [U.S.A.] New element 94239 by irradiation of 1.2kg uranium oxide with neutrons emitted from beryllium irradiated by deutron.1 microgram of element was obtained. E. Segre and G. Seaborg.
1941.3.17 [U.S.A.] E. Lawrence proposes promotion of "uranium plan" based on conviction of the enriching method of uranium-235 utilizing cyclotron.
1941.3.28 [U.S.A.] Verification of nuclear fission of new element 94239by E.Segre,G.Seaborg and Joseph Kennedy. Irradiation of new element 94by paraffin-decelerated neutron emitted from beryllium irradiated by deutron. About 1.5 times of that by uranium irradiation.
1941.3 [U.S.A.] Improved measurement of cross section of uranium235by M.Tuve (the result was transmitted to England).
1941.3 [England] Critical mass of uranium235 calculated by R.Peierls.
1941. 3 [U.S.A.] Lend-Lease Act. President Roosevelt proposed to help Britain and other countries defend themselves against Germany.
1941.4 [Japan] Army approves atomic bomb research.
1941. 5 [United Kingdom] Klaus Fuchs, a German emigre theoretical physicist, a student of R. Peierls, started research of atomic bomb. A stalwart communist and Soviet espionage agent.
1941. 6.22 [Germany] Invasion by Hitler into Soviet Union.
1941. 7. 3 [U.S.S.R.] Formation of State Defence Committee (GKO)
[Stalin,Molotov,Voroshilov,Malenkov and Beria]
1941.5.18 [U.S.A.] Cross section of new element 94239 assessed by E.Segre and G.Seaborg. Nuclear fission caused by slow neutron is 1.7times of that in uranium235.
1941.5 [Japan] A lecture by Tokutaro Hagiwara of explosive uranium235.
1941.6.23 [England] George Paget Thomson and MAUD committee reports convincing evidence of developing uranium235bomb.
1941.7.7 [England] The conclusion of MAUD committee transmitted to U.S.A.
1941.7.11 [U.S.A.] A memorandum regarding a nuclear fission of the94th element by E.Lawrence. (Possibility of plutonium bomb)
1941.7.24 [U.S.A.] The cross section of new element 94239:The nuclear fission caused by slow neutron is 3.4 times of that of uranium238.
1941.8 [England] Encouragement by M.Oliphant to nuclear power project in U.S.A.
1941.9 [U.S.A.] Triggering by atomic bomb of hydrogen bomb studied by E. Fermi and E. Teller.
1941.9 [U.S.A.] Construction of a graphite pile started by E. Fermiand L. Szilard.
1941.10.9 [U.S.A.] MAUD report brought to President Roosevelt by Vannevar Bush. Atomic bomb development project started with transferring the focus from nuclear reactor to atomic bomb.
1941.10 Discussion by N. Bohr and W. Heisenberg of a heavy water type pile in Copenhagen.
1941.11.6 [U.S.A.] The 3rd NSA report of Compton committee. (Uranium bomb possible within 3-4 years. Fifty to one hundred million dollars for uranium enriching plant.)
1941.11.27 [U.S.A.] Submission of the 3rd NAS report to President Roosevelt.
1941.11 [U.S.A.] Separation of uranium235 by J.Dunning and U.Booth. (A gas dispersion method using uranium fluoride(VI).)
1941.12.1 [U.S.A.] Data of nuclear fission of new element 94239given to A.Compton by E.Lawrence.
1941.12.2 [U.S.A.] Separation of 100 micrograms uranium235by E.Lawrence.
1941.12.6 [U.S.A.] Submission of plutonium bomb project by A.Compton.
1941.12.6 A counterattack to Germany corps by Soviet Union in Moscow.
1941.12.8 [Japan] A surprise attack on Pearl Harbor. (In U.S.A. date was 12.7)
1941.12.9 [U.S.A.] A plutonium bomb project started by A. Compton and V. Bush without report to President Roosevelt.
1941.12.16 [U.S.A.] V. Bush required participation of Engineering Brigade in atomic bomb project.
1941.12.18 [U.S.A.]OSRD creates the S-1 committee, a special committee created by V.Bush. [Connant, Briggs, Pegram, Compton, Lawrence, Urey, Samuel Allison, G.Bright, Edward Condon and Henry DeWolf Smyth]
1941.12.20 [U.S.A.] Budget for developing atomic bomb of $651,000 (half year portion) authorized.
1941.12 [U.S.A.] Calutron built by E.O. Lawrence: A 184-inch cyclotron to separate U235. By the summer of 1942 most of the design problems had been solved. The new machine was named Calutron after the University of California.

Atomic Bomb Chronology: 1942-1944                                                                            top

1942.1.24 [U.S.A.] Concentration of the atomic power research (Pile Plan) to the Chicago's Metallurgical Laboratory. [A. Compton, E. Lawrence,L. Szilard and others]
1942. 9 [U.S.S.R.] Soviet Atomic Bomb Project started. Led by Igor Vasilievich Kurchatov(40 years old).
1942.3 [U.S.A.] Naming of new elements by G.Seaborg: Neptunium for93 and Plutonium for 94. (Named for planets Uranus, Neptune and Pluto)
1942.3 [Soviet Union] Beria, the director of secret police, reports western situation of the nuclear development to Stalin, based on spy's information.
1942.4.18 [U.S.A.] The first bombing of Tokyo by several B-25 bombers taking off an aircraft carrier "Hornet" in the Pacific Ocean.
1942.4.23 [U.S.A.] Chemistry Conference at Chicago Metallurgical Laboratory[G.Seaborg,E.Wigner,J.Wheeler and others] on plutonium-separation technology including precipitation method.
1942.4 [U.S.A.] An experimental facility for ultra-micro chemical analysis established at Chicago Metallurgical Laboratory.
1942.4 [Soviet Union] A letter from G. Flerov to Stalin estimating western development of nuclear fission technology from the fact that papers relating to nuclear fission were gone from scientific journals.
1942.5.14 [U.S.A.] J. Conant's report of the atomic bomb development research presented to V. Bush, director of the Carnegie Institution of Washington.
1942.5.15 [U.S.A.] Delayed neutrons are below 1% of prompt neutrons. K (criticality factor) of prompt neutron is 1 or less and K including delay neutron is 1 or more.
1942.5.18 [U.S.A.] G. Bright resigned the person in charge of nuclear fission study using fast neutron claiming insufficient secrecy. He required a new research institute.
1942.5.26 [U.S.A.] Magnets for cyclotron of 184 inches that develops Calutron completed. Gross weight was 4000 t.
1942.5 [U.S.A.] The designing of Chicago Pile number 1 (CP-1) starts.[E.Fermi, H.Anderson]
1942.6.5 Japanese corps defeated at Midway naval battle.
1942.6.11 [U.S.A.] R. Oppenheimer named as successor of G.Bright: Arrived at Chicago to research nuclear fission caused by fast neutrons.
1942.6.13 [U.S.A.] 'Nuclear fission bomb' report to the president submitted by V. Bush and J. Conant. Scientists are convinced of feasibility of plutonium plan.
1942.6.17 [U.S.A.] The production of plutonium started. 45-inch cyclotrons of St. Louis University and Washington University were used. 136 kg uranium nitro-oxide(VI) was irradiated continuously for one month.
1942.6.17 [U.S.A.] President Franklin Roosevelt authorized the atomic bomb development plan.
1942.6.25 [U.S.A.] The 1st S-1 committee meets. Participants: Conant,Briggs, Compton, Lawrence, Urey, Murphrey, Major General Wilhelm D. Styer,Colonel George C.Marshall, Colonel Kenneth D. Nichols. Centrifuge separation method and gas dispersion method were unfinished. Electric power required was estimated as 108,000 KW.
1942.6.27 [U.S.A.] Conference at Chicago's Metallurgical Laboratory.[Compton, Allison, Fermi, Seaborg, Szilard, Teller, Wigner, Walter Zinn].Start of feasible nuclear warfare study encouraged by A.Compton.
1942.7.9 [U.S.A.] S-1 committee approves construction of heavy water factory at Canada Trail. Order given to Consolidated Co.
1942.7.27 [U.S.A.] Plutonium arrives at Chicago from St. Louis.
1942.7 [U.S.A.] The Berkley summer study. A. Compton had asked theoretical physicist J. Robert Oppenheimer of the University of California-Berkleyto study the feasibility of a nuclear weapon. Oppenheimer convened a summer study at UC-Berkley. [Oppenheimer, H.Bethe, E.Teller, John Van Vleck, FelixBloch, Richard Tolman, Emil Konopinski, Robert Serber, L.Alvarez, J.Lawson,Robert Thornton, Robert Becker] Feasibility concluded. The chief uncertainties lay in the experimental values for neutron cross-sections, numbers of neutrons that would be produced in fission and cause other atoms to fission in a rapid chain reaction. The scientists suggested that such a reaction could be initiated by assembling a critical mass--an amount of nuclear explosive adequate to sustain it--either by firing two subcritical masses of plutonium or uranium 235 together or by imploding (crushing) a hollow sphere made of these materials with a blanket of high explosives (Tolman). Teller saw another possibility: by surrounding a fission bomb with deuterium and tritium, a much more powerful "superbomb" might be constructed. This concept was based on studies made by Bethe before the war of energy production in stars. When the detonation wave from the fission bomb moved through the mixture of deuterium and tritium nuclei, they would fuse together to produce much more energy than fission, just as elements fused in the sun produce light and heat. The summer conferences, the results of which were later summarized by Serber in "The Los Alamos Primer" (LA-1),provided the theoretical basis for the design of the atomic bomb, which was to become the principal task at Los Alamos during the war, and the idea of the H-bomb, which was to haunt the Laboratory in the postwar era. Seldom has a physics summer school been as portentous for the future of mankind. By Robert Seidel.
1942.8.11 [U.S.A.] Manhattan Engineering District (MED) created by Colonel James C. Marshall.
1942.8.20 [U.S.A.] Plutonium separated as a solid by Burris Cunningham and Louis B.Werner.
1942.9.14 [U.S.A.] Purchase of the uranium ore advised by S-1 committee.
1942.9.17 [U.S.A.] Colonel Leslie R. Groves (46 years old) is appointed to the commander of MED and the director Manhattan Project.
1942.9.18 [U.S.A.] Uranium ore purchased: 1250 tons stored in open-air on Staten Island since 1940.
1942.9.19 [U.S.A.] The highest priority of supply given to Manhattan Project by War Production Board.
1942.9.21 [U.S.A.] L. Groves and J. Marshall visit the Navy Research Institute.
1942.9.23 [U.S.A.] L. Groves promoted to Brigadier General.
1942.9 [U.S.A.] Trouble at Chicago: Repellence by L.Szilard, E.Fermi, J.Wheeler and others to Stone & Webster Co.
1942.9 [U.S.A.] Clinton, Tennessee (Site X): 5200 acres site purchased for factory of separation of Uranium235. Oak Ridge is the name of residence area. For full-scale production of enriched uranium and for the pilot-scale production of plutonium.
1942.9 Anglo-French atomic power accord.
1942.10.5 [U.S.A.] L. Groves visits Chicago's Metallurgical Laboratory.
1942.10.18 [U.S.A.] L. Groves, V. Bush and J.R. Oppenheimer talk at Berkeley:
1942.11.5 [U.S.A.] Construction of production plant with the electromagnetic separation method ordered by L. Groves to Stone and Webster Co. [Electric supply by General Electric; magnets by Allice Chalners; container by Westinghouse.]
1942.11.10 [U.S.A.] L. Groves generally entrusts the "PlutoniumProject" to DuPont Corp. (Carpenter, president of DuPont, proposed another plutonium production factory site than Clinton.)
1942.11.12 [U.S.A.] Construction of uranium-235 production plant decided by Military Policy Committee. Without construction of small scale testing pilot plants.
1942.11.14 [U.S.A.] Pilot plant omission approved by MED Review Committee. Plutonium plan is entrusted to DuPont, not to Stone & Webster.
1942.11.16 [U.S.A.] Looking for a suitable site for a new laboratory to design nuclear weapons: [Groves, Oppenheimer, McMillan and Major John Dudley.] Los Alamos was recommended by Oppenheimer rather than Jemes Springs the place Dudley, an officer entrusted with search, had selected.
1942.11.16 [U.S.A.] The construction of Chicago Pile number 1 (CP-1):[E.Fermi,W.Zinn,Herbert.Anderson]
1942.12.2 [U.S.A.] Self-sustaining chain reaction in Chicago Pile number 1 ( Critical State) [Fermi, Zinn, Anderson] Output 50W, 4.5minutes operation. 350 t pure graphite, 35 t metallic uranium. Eugene Wignerhanded Fermi a bottle of Bertolli Chianti and passed around paper cupsto the crew. Arthur Compton called the head of the NDRC, James Conant, and told him cryptically, " the Italian navigator has just landed in the New World," the secret phrase agreed to, signaling success. On12.12 output rose to 200W.
1942.12.4 [U.S.A.] L.Szilard opposed by L.Groves for a security clearance because he is a foreign citizen. Finally Szilard, because of his earlier brilliant works, was treated like E. Fermi and E. Wigner.
1942.12.23 [U.S.A.] Feasibility of plutonium plan reported by A.Comptonto L.Groves. The first atomic bomb was scheduled to be completed by 1945.Later, it would be possible to produce one per month.
1942.12.28 [U.S.A.] DuPont Corp. takes charge of the plutonium plan. he reward other than the necessary expense was 1 dollar.
1942.12 [U.S.A.] Construction of a plant with gas dispersion method(K25) entrusted to Kellex Co. by L.Groves. An independent power supply was also constructed not relying on TVA.
1943.1.4 [U.S.A.] Uranium enrichment by liquid thermal dispersion method is reported by R.Gunn and P.Abelson. Navy was not told of the critical state of Chicago Pile.
1943.1.15 [U.S.A.] Pile design at Clinton commenced. Water cooling was suggested by E.P. Wigner.
1943.1 [U.S.A.] L.Groves entrusts the operation of the production plant with the gas dispersion method to Union Carbide Co.
1943.1 [Soviet Union] Development of nuclear weapons is decided.
1943.2.1 [U.S.A.] Plutonium plant site at Hanford(Site W) outside of Richland ,Wash. Cost: $5,100,000.
1943.2.2 [Soviet Union] German army corps surrenders in Stalingrad, USSR.
1943.2.18 [U.S.A.]. Construction of uranium235 separation factory (Queen Mary) at Clinton starts.
1943.2.27 [England] Explosion of German heavy water factory in Norway by Norwegian resistance. German nuclear research was greatly hindered.
1943.3.6 [Japan] Navy gives up atomic bomb development. Priority shifted to the radar research.
1943.3.15 [U.S.A.] J.Robert Oppenheimer (38 years old) arrives at LosAlamos as the director.
1943.3.17 [U.S.A.] Design specification of Calutron decided
1943. 3.22 [U.S.S.R.] Kurchatov made attention to Plutonium. Study of back numbers of Physical Review. Asking to set Soviet intelligence to find out British and the American progress.
1943. 3 [U.S.A.] A American officer named George Racey Jordan in charge of expediting deliveries through the Gore Field, Air Port for Lend-Lease to Soviet Union, suspected Soviet's transport of US confidential contained in many black suitcases. His report to Washington was ignored. Transport of nuclear materials was later revealed.
1943.3 [U.S.A.] XA magnet for Calutron completed: The radius of gyration: 3-4 feet. Magnetic field: 3410 oersted.
1943.4.1 [U.S.A.] N-A barrier for the gas dispersion method entrusted by L.Groves to Widell Hershey Co.
1943.4 [U.S.A.] Los Alamos starts: [J.R. Oppenheimer, John Manley,H. Bethe, E. Teller, E. Kopinowsky, Felix Bloch, Stanley Frankel, Eldred Nelson, Robert Serber, Robert Wilson, Richard Feynmann, John Williams and many others]. Average age, 26 years old. Finally 3000 people. Edward Condon left soon after opening hating militaristic regulation.
1943.4 [U.S.A.] Implosion Method for firing A-bomb proposed by Seth Neddermeyer. Blowing a sphere of uranium-235 or plutonium would assemble these materials so rapidly that they explode.
1943.5.25 U.S.A.- England talks at the White House on Churchill's request for information of atomic bomb.
1943.6 [U.S.A.] William Parsons, Commander (43 years old) arrived at Los Alamos. A technology officer dealing with radar, he later engaged in dropping of Little Boy.
1943.7.2 [Japan] Yoshio Nishina reports the feasibility of A-bomb to army. Employing thermal diffusion method.
1943.7 [U.S.A.] Number of secondary neutrons from fission of plutonium assessed as 2.9 by Robert Wilson with material obtained by 184-nch cyclotron at Los Alamos.
1943.7.17 [U.S.A.] Starting of test shot of gun-type ignition. [W.Parsons]
1943.7.22 England - U.S.A. talk of about A-bomb at Downing Street 10.[Churchill, Sir John Anderson, Lord Cherwell, Henry H.Stimson, V. Bush, Harvey H. Bandy]. Bush promised Churchill to convey his concern for Soviet Union's threat.
1943.7.24 Indiscriminate bombing of Hamburg: the first carpet bombings with 7.28 bombs per second. A huge fire storm developed.
1943.7.25 [Italy] Mussolini is arrested and executed.
1943.8.19 Quebec Conference. [Winston Churchill, Franklin Roosevelt].Without mentioning about an international agreement regarding to atomic bomb development or Anglo-French atomic power accord.
1943.8.29 [Germany] Disarmament of Denmark corps.
1943.9 [U.S.A.] John von Neumann arrives at Los Alamos to support S.Neddermeyer's implosion group with a mathematics division.
943.9.29 Niels Bohr escapes to Sweden by a motor boat. Protection of Denmark- residing Jews was appealed to Swedish government.
1943.10.6 [England] N. Bohr seeks refuge in England on the flight of a Mosquito bomber. Due to altitude anoxia he fainted. His son Aage Bohr arrived at London after one week . R. Tolmann, as a visitor to England, transmits an invitation by L. Groves to the Manhattan Project.
1943.10 [U.S.A.]. Calutron constructed. Due to shortage of copper for coil of electromagnet, silver owned by Department of Treasury was used. To the request of 5 - 10 tons, Department of Treasury replied that they weigh silver by troy ounce. 395,000,000 Troy ounce, worth $300,000,000dollars. A race-truck on the 2nd floor; vacuum pump room on the 1st floor; operation personnel 4800 people.
1943.10 [U.S.A.] Start of construction of Hanford pile (100-B) for production of plutonium.
1943.10 [U.S.A.] Critical state produced by the implosion method.[J.V. Neumann, E. Teller] Critical state produced by compression of explosive substance less than critical mass because of less escape of neutrons.
1943.11.4 [U.S.A.] The critical state of Clinton Pile (Oak Ridge, X-10):800 KW; air cooling with blower; A graphite atomic pile; 7.5KW: 1944 Feb.,1800KW 1944. June, 3800KW: Owed greatly to G.Seaborg.
1943.11.16 [England] Bombing of German heavy water factory in Norway by B-17 bombers. Heavy water factory exploded previously was repaired April. Germany decided to move the factory to Germany.
1943.11.20 [U.S.A.] Start of separating plutonium at Clinton, processing with a remote control plant of 5 tons of uranium bombarded by neutrons.
1943.11.29 [U.S.A.] Start of remodeling B-29 bomber for A-bomb. [Norman Ramsey. External size of bomb decided. Thin Man (for Roosevelt) and Fat Man (for Churchill)]. (N.F.Ramsey received Nobel Prize in 1989.)
1943.12. 3 British Mission: English scientists join Manhattan Project(Quebec accord) [Wallace Ackers, Otto Frisch, R. Peierls, William J. Penny,George Placzek, P.B. Moon, James L. Tuck, Egon Bretcher, Klaus Fuchs, James Chadwick, Geoffrey Taylor, Niels and Aage Bohr]
1943.12.14 [U.S.A.] U. S. Army Special Corps (ALSOS) landed in Italy: [Commander Boris T. Pash] Confirmation of improbable German development of A-bomb. This was not passed on to the Manhattan Project scientists.
1943.12.22 [U. S. A.] Impossibility of production of N-A barrier for gaseous diffusion method found in study by F. Simon and R. Peierls.
1943.12.31 [U. S. A.] Possibility of pile as a weapon considered by R. Oppenheimer, N. Bohr and others.
1943.12 British Mission: English scientists join Manhattan Project(Quebec accord) [Wallace Ackers, Otto Frisch, R. Peierls, William J. Penny,George Placzek, P.B. Moon, James L. Tuck, Egon Bretcher, Klaus Fuchs, James Chadwick, Geoffrey Taylor, Niels and Aage Bohr.]
1943.12 [U. S. A.] Nuclear fission of uranium235caused by neutrons in cosmic rays discovered by E.Segre. Possibility of slowing down of core reaction speed implied. Change to Little Boy from Thin Man. The full length from 17 feet to 6 feet.
1944.1 [U. S. A.] A new type barrier for gaseous diffusion method(J barrier) employed.
1944.1 [U. S. A.] George B. Kistiakowsky arrives at Los Alamos for the chemical explosive division supporting Neddermeyer's implosion device.
1944.1 [U. S. A.] Start of navy liquid thermal diffusion plant construction:300 columns. [P.Abelson]
1944.2.1 [U. S. A.] Separation of plutonium at Clinton plant finished. A pilot test. 190 mg.
1944.2.20 [England] Sink of German heavy water, blasting of boat transporting from Norway to Germany. End of German development of nuclear weapons.
1944. 2 [U.S.A.] Klaus Fuchs met with Harry Gold, a Soviet intelligence agent.
1944.2 [Japan] A report by Yoshio Nishina indicating difficulty of production of uranium fluoride. The method considered was that had been given up by P. Abelson.
1944.3.1 [U. S. A.] The first plutonium 239 from Clinton arrives at Los Alamos.
1944.3.3 [U. S. A.] Start of test dropping of atomic bombs by B-29.Dropping of mock bomb of Thin Man bomb failed due to hitting against bomb-bay door.
1944.3.27 Belgium government sells the pre-emption of all the uranium resource in Congo to U.S.A. and England. [Sir John Anderson, Ambassador John G. Winant] for $375,000,000 dollars.
1944. 3 [U.S.A.] Fuchs leaked data (including draft of his own paper) of gaseous diffusion to Soviet agent.
1944.3 [U. S. A.] The first transportation of enriched uranium 235from Clinton to Los Alamos. 10% enrichment.
1944.3 [U. S. A.] Kenneth T. Bainbridge is assigned to the responsible person of the first A-bomb test, Trinity. Trinity named by J. Oppenheimer.
1944.3 [U. S. A.] Peppermint operation: Portable Geiger counters, X-ray films and so on for inspecting radioactivity were prepared for Normandy invasion by Allied forces.
1944.3 [U. S. A.] Prediction of fireball associating with A-bomb explosion by H.Bethe and Robert Christy. Emergence of a fireball and impulse wave of air heated by soft X-rays given out in chain raction.
1944.4.28 [U. S. A.] Liquid thermal diffusion method for enriching uranium235 is recommended by J.Oppenheimer to L.Groves.
1944.4 [U. S. A.] Explosive Lens for ignition of A-bomb: An idea developed by James L. Tuck. Production of spherical impulse wave by combinatorial ignition of explosives with various burning velocity.
1944.4 [U. S. A.] IBM computer arrival at Los Alamos. [J. Neumann, Stanislaw Ulam] For the hydrodynamics of implosion, and interference of impulse waves.
1944.5.16 Churchill - N.Bohr talk: Bohr's suggestion on international cooperation of A-bomb development, treatment of Soviet Union. His apocalyptic viewpoint was not understood.
1944.5 [U. S. A.] R. Peierls moved to theory division by J.Oppenheimer.
1944.5 [U. S. A.] Calutron completion: A new plant for uranium235high enrichment: radius, 2 feet.
1944.5 [U. S. A.] Alamogordo Bombing Range chosen for Trinity by J.Oppenheimer and K.Bainbridge.
1944.6.6 D-day: Normandy invasion by allied forces. D.Eisenhower commanding.1500 tanks, 12,000 airplanes, 156,000 soldiers, 1200 battleships.
1944.6.12 [U. S. A.] A liquid thermal diffusion plant at Clinton approved.
1944.6.13 [Germany] V-1 rocket bombs London: 8070 rockets were launched by 1944.9.4. 29% of them flew to London.
1944.6 [U. S. A.] G. Kistiakowsky as director of explosive section. S.Neddermeyer withdrew as an adviser.
1944.6 [U. S. A.] Highly enriched uranium 235 from Clinton arrived at Los Alamos.
1944.7.11 [U. S. A.] Absence of feasibility of Plutonium bomb, concluded.[Midsummer Crisis] Too much plutonium240 was detected in Clinton sample by E.Segre. J.Oppenheimer was persuaded not to resign by RobertF. Backer.
1944.7.17 [U. S. A.] The highest priority is given to "IMPLOSION"by J.Oppenheimer. The abandonment of THIN MAN. Implosion at 10 km/sec is required in Plutonium bomb. Feasibility was considered of an implosive type uranium bomb in order to obtain multiple bombs.
1944.8.1 [U. S. A.] Tinian Is. occupation: 6 runways for B-29 bombers were made for attacking Japan.
1944. 8. 5 [U.S.A.] David Greenglass, a communist, joined Los Alamos for supporting development of implosion lens.
1944.8.7 [U. S. A.] Time table of A-bomb production presented by L.Groves. Several bombs may be made until March-June ,1945 if implosion method is effective. Otherwise, one bomb is produced by August, 1945.
1844. 8.14 [U.S.A.] Klaus Fuchs joined Los Alamos. Chadwick informed Fuchs that his service was requested.
1944.8.25 [U. S. A.] Advance into Paris by U. S. Army. Special unit(ALSOS) advanced into Paris next to tanks. [B.Pash, Samuel A. Goutsmit].They questioned F.J. Curie at the Radium Research Institute and confirmed the absence of German A-bomb development.
1944.8.26 Roosevelt - N.Bohr talk. Suggestion by Bohr on international cooperation of A-bomb development , treatment of Soviet Union. His apocalyptic viewpoint was not understood.
1944.8 [U. S. A.] Colonel Paul W. Tibbets (29 years old) made commander of the 509th Composite Group. He was a test pilot of B-29 bomber.
1944.8 [U. S. A.] General Curtis LeMay made commander of the 20thbomber corp. A strategy of taking off Chinese base for bombing Japan considered.
1944.9.8 [Germany] V-2 rocket bombing of London: 4320 rockets were launched till March 27, 1945. 1050 of them dropped on England.
1944.9.13 [U. S. A.] Start of charging of metal uranium at Hanford Pile: 250 t uranium, 100,000 rods of graphite,11m×8.5mH)
1944.9.18 Hyde Park Accord reached. [F. D. Roosevelt and W. Churchill]A secret accord deciding atomic bombing of Japan.
1944.9.19 [U. S. A.] A note of post-war strategy: Sent by V.Bush andJ.B.Connant to Henry L.Stimson, the secretary of war. Danger of making A-bomb secret. Participation of Soviet Union to any accord is essential.
1944.9.19 [U. S. A.] Seizure by ALSOS of German uranium ore (68 tons). [B.Pash] 30 tons were found in Toulouse, October ,1944.
1944.9.26 [U. S. A.] The critical state achieved in Hanford Pile. Operation with 9MW. Rising of cooling water temperature from 10 to 60 deg C. It was due to absorption by xenon135, a fission product, of neutrons. Cross section of xenon135 of neutron-absorption is 150 times of cadmium. Critical state in the 2nd Pile in December 1944. Critical state in the 3rd Pile in 1945.
1944. 9 [U.S.A.] Robert Christy proposed a bombing core not a shell of plutonium but a nearly solid subcritical ball (in the form of two fitted hemispheres). The imploding detonation wave would simply squeeze the solid mass to criticality.
1944.9 [U. S. A.] Start of Calutron operation: 100 g daily production of 10% enriched uranium.
1944.10.25 [Japan] Kamikaze commando at Layte naval battle.
1944.10.30 [U. S. A.] Start of operation of Navy liquid thermal diffusion plant at Philadelphia navy arsenal.
1944.10 [U.S.S.R.] Production of plutonium(several micrograms) by Boris Kurchatov [a brother of Igor Kurchatov]
1944.11.24 [U. S. A.] Bombing Japan by B-29 bombers from Northern Mariana base with a large formation of 100 bombers. The high altitude bombing failed due to a high speed air current. The discovery of jet stream.
1944.11.28 [U. S. A.] Taking out of irradiated slugs from Hanford Pile:8.3 tons.
1944.11 [U.S.S.R.] Metallic uranium refined.
1944.11 [U. S. A.] Start of operation of Calutron: 90 g daily production of 80% enriched uranium.
1944.11 [U. S. A.] Start of implosion experiment with shaped explosives. Implosive process was examined by X-ray camera taking hi-speed successive pictures.
1944.12.26 [U. S. A.] Separation of irradiated slugs from Hanford Pile.
1944 [U. S. A.] A balloon bomb from Japan cuts the power supply to Hanford Pile.

Atomic Bomb Chronology: 1945-1946                                                                             top

 

1945.1.2 [U.S.A.] David Greenglass's contact with Julius Rosenberg, a Soviet intelligence agent, handing a sketch of implosion lens and a list of asset candidates.
1945.1.16 [U. S. A.] Start of plutonium separation at Hanford.
1945.1.20 [U. S. A.] Start of operation in the gaseous diffusion plant using a supply of poorly enriched uranium to Calutron. Development of teflon as a sealant.
1945.1.20 [U. S. A.] Low altitude incendiary bombing of Japan proposed by C.LeMay, Commander of B-29 bombers corps.
1945.1 [U. S. A.] Verification of critical mass of uranium235by Otto Frisch. Named Dragon experiment by R. Feynman. Accident in February of neutron irradiation. A victim died.
1945.1 [U. S. A.] An ignition device for implosion completed by Luis W. Alvarez.
1945.2.4 Yalta talk. F. Roosevelt, W. Churchill and Y. Stalin. Demanded unconditional surrender of Japan: A secret agreement of attacking of Japan by Soviet Union.
1945.2.5 [U. S. A.] Transport of plutonium239 from Hanford to Los Alamos as nitric acid solution.
1945.2.7 [U. S. A.] Implosion lens completed by G. Kistiakowsky.
1945.2 [U. S. A.] Schedule of Trinity test decided. Implosion will be employed only in plutonium bomb.
1945.2 [U. S. A.] Start of operation in Liquid Thermal Diffusion plant, supplying poorly enriched uranium to Calutron. After June, uranium was processed in the order of liquid thermal diffusion plant, gaseous diffusion plant and Calutron. Improvement of enrichment with gaseous diffusion plant.
1945.2 [U. S. A.] Tinian recommended as the Dispatch base for A-bomb B-29 by commander Frederick L. Ashworth.
1945.2.16 [U.S.A.] Klaus Fuchs handed Soviet intelligence agent data of implosion system. He refused to receive 1500 dollars reward.
1945.2.28 [U.S.A.] Leaders of Manhattan Project including Groves, Office of Scientific Research and Development section head and Harvard President James Bryant Conant, Hans Bethe, George Kitiakowsky and Richard Tolman met in Oppenheimer's office and decided tentatively to develop the lensed, solid-core Christy implosion design as a combat weapon.
1945.3.10 [U. S. A.] 100,000 victims killed in large air attack on Tokyo: 234 B-29 bombers with 1665 tons of incendiary bombs.
1945.3.15 [U.S.A. Germany] US air force attacked Metal-refining plant in Oranienburg (15 miles north of Berlin) to prevent German production of metallic uranium.
1945.3 [Germany] Start of experimental operation of B-8 nuclear reactor by W. Heisenberg, K. Diebner, Carl F. von Weizsaocker, Hans Bethe and others. A cylinder type reactor employing graphite as neutron reflector and heavy water as modulator. Did not achieve the critical state.
1945.4.12 [U. S. A.] Verification of critical mass of Plutonium 239 by O.Frisch in Dragon Experiment.
1945.4.12 [Japan] Riken Scientific Institute destroyed: End of Japanese A-bomb project.
1945.4.12 [U. S. A.] Sudden death of President Roosevelt. Replaced by Harry S. Truman, the vice president. H. Stimson first explained Manhattan Project to President Truman in the evening.
1945.4.17 [Germany] German uranium ore found by commander John Lansdale, Jr. of US army special unit (ALSOS). At a shed in Stuttgart. Supplied to Manhattan Project
1945.4.23 [Germany] Reactor at Heigerloch seized by U.S. army (ALSOS). Commanders B. Pash and Samuel A. Goudsmit. Goutsmit is Heisenberg's friend. Goutsmit's parents had been killed by Nazi in a gas chamber.
1945.4.24 [Germany] German atomic scientists arrested in Hebingen. [C. Weizsaecker, O. Hahn, Max von Laue]
1945.4.25 [U. S. A.] Truman and Stimson discuss details of Manhattan Project.
1945.4.26 [Germany] Metal uranium and heavy water found by ALSOS.
1945.4.27 [U. S. A.] The 1st Target Committee meets. [L.Groves, Thomas F.Farrell,J.Neumann and William G.Penny] Japan, July or August. Visual flying by a B-29 bomber with the range of 2500km or less.
1945.5.1 [Germany] Death of Adolf Hitler.
1945. 5. 2 [Germany] Berlin occupied.
1945,5.3 [U. S. A.] W. Heisenberg arrested by U. S. army ALSOS in Welfeld.
1945.5.8 [Germany] Germany surrenders to allied forces.
1945.5.9 [U. S. A.] Interim committee on nuclear power meets: Henry Stimson, Ralph Bard, Vannevar Bush, James Byrnes, William Clayton, Karl Compton, George Harrison: By invitation: Harvey Bundy. Predicts development of nuclear weapons by Soviet Union in 7 years.
1945.5.10 [U. S. A.] The second Target Committee meets in Los Alamos: L. Groves, General Farrel, Colonel Seeman, Captain Parsons, C. Lauritsen, Major Derry, Drs Ramsey, Dennison, Stearns, Tolman, Oppenheimer, von Neumann, Wilson, Penny, Bethe, Robert. The first choices of targets for nuclear weapons are: a. Kyoto, b. Hiroshima, c. Yokohama, d. Kokura Arsenal.
1945.5.25 [U. S. A.] Operation of Kyushu invasion decided by Douglas MacArthur (army), Chester Nimitz (navy) and Henry H. Arnold (army air corps). Named " Operation Olympiad," scheduled for November 1.
1945.5.28 [U. S. A.] Joseph C. Grew, undersecretary of the State Department, of predicts Japanese surrender to President Truman.
1945.5.28 [U. S. A.] L. Szilard expresses his opinion against use of A-bomb to Presidential advisor J. Byrnes. Rejected.
1945.5.28 [U. S. A.] The third Target Committee meets. Given report of test bombing carried out in Cuba by Colonel P. Tibbets.
1945.5.30 [U. S. A.] Stimson tells L. Groves to exclude Kyoto from list of A-bomb targets.
1945.5.31 [U. S. A.] Recommendation on the immediate use of nuclear weapons given by the Interim Committee: Byrnes, Stimson, G. C. Marshall, Groves, Harvey H. Bundy, J. Conant, Compton, Lawrence, Fermi, Oppenheimer. Inviting Soviet Union to Trinity proposed by Oppenheimer. Decided not to notify Japan before dropping A-bomb. Objections by Szilard discussed.
1945.5 [U.S.S.R] German 130 tons uranium oxide found in a tannery in Berlin right on the border of American-occupied territory was seized by Soviet army and shipped to Soviet Union.
1945.5 [U. S. A.] Joseph Rotblat resigns of from Los Alamos because of Germany's surrender. Later he founded Pugwash Conference.
1945.5 [Soviet Union] German uranium seized: over 100 tons in Belgium.
1945.6.2 [U.S.A.] Confidential data including information of Trinity, atomic bomb, explosive materials handed by Klaus Fuchs to a Soviet agent.
1945.6.3 [U.S.A.] David Greenglass handed to the same agent contacting with Klaus Fuchs the sketch of implosion lens and names of asset candidates. Received 500 dollars reward.
1945.6.6 [U. S. A.] Recommendation of A-bomb use by Interim Committee conveyed to President Truman by Stimson.
1945.6.10 [U. S. A.] The 509th Composite Group arrives at Tinian with 11 B-29 bombers.
1945.6.11 [U. S. A.] James Frank committee recommends notification before use of A-bomb: J. Frank, Leo Szilard, Eugene Rabinowitch. Seven scientists in Chicago recommended a show of force demonstration.
1945.6.18 [U. S. A.] Estimation of 63000 war dead or wounded in Operation Olympiad (Kyusyu invasion) by General G.C.Marshall.
1945.6 [U. S. A.] Assembly of the plutonium bomb for Trinity.
1945.7.2 [U.S.S.R.] Confidential data obtained by espionage agents from USA were shown to Igor Kurchatov.)
1945.7.3 [U. S. A.] Casting of a warhead for uranium235 bomb.
1945.7.12 [U. S. A.] Plutonium core arrives at Alamogordo.
1945.7.13 [U. S. A.] Explosive assembly arrival at Alamogordo.
1945.7.14 [U. S. A.] A preparatory implosive experiment for Trinity failed. The defect explosive was replaced by hand work.
1945.7.14 [U. S. A.] Gadget for Trinity completed by Norris E. Bradberry and others. Installed at top of 30m high tower.
1945.7.15 [U. S. A.] Preparatory implosion experiment declared indecisive by H. Bethe.
1945.7.16 [U. S. A.] TRINITY test. After 90 minute delay for bad weather, at 5:29:45. Explosive force of 18.6 kilotons of TNT.
1945.7.16 [U. S. A.] Shipping of Little Boy by cruiser Indianapolis, 4 hours after Trinity.
1945.7.17 [U. S. A.] Petition to President Truman against the use of nuclear weapons by L. Szilard and 70 scientists.
1945.7.20 [U. S. A.] Allied Commander D. Eisenhauer advises President Truman not to use A-bomb; it is unnecessary.
1945.7.21 [U. S. A.] Report from L. Groves of successful Trinity conveyed to President Truman staying in Potsdam: Later W. Churchill told H. Stimson that Truman's reaction was clearly observable.
1945.7.23 [U. S. A.] Telegraph by George L.Harrison to Potsdam informing that dropping A-bomb on Japan is possible after August 1.
1945.7.23 [U. S. A.] Completion of the 2nd plutonium core.
1945.7.24 [U. S. A.] H. Truman told Y. Stalin about A-bomb experiment. Stalin was already informed by spy of Trinity but never revealed it.
1945.7.25 [U. S. A.] Approval by President Truman staying at Potsdam of the order to bomb Japan with A-bomb. The order was written by L. Groves.
1945.7.26 [U. S. A.] Cruiser Indianapolis arrives at Tinian. Little Boy is unloaded.
1945.7.26 [U. S. A.] Shipping of uranium-235 warhead to Tinian: by C-54 transport plane.
1945.7.26 [U. S. A.] Shipping of plutonium core and the initiator to Tinian by C-54 transport plane.
1945.7.26 Potsdam Declaration announced, demanding unconditional surrender of Japan.
1945.7.30 [U. S. A.] Cruiser Indianapolis sunk by a torpedo attack from a Japanese submarine, only 4 days after unloading of A-bomb.
1945.7.31 [U. S. A.] Assembling Little Boy, waiting recovery of weather.
1945.8.2 [U. S. A.] Parts of Fat Man arrive at Tinian.
1945.8.4 [U. S. A.] Briefing to crew of B-29 bombers of the 509th corps. Presentation by William Parsons of documentary film of Trinity.
1945.8.5 [U. S. A.] Bombing date of August 6 decided by Curtis LeMay. Installation of Little Boy in a B-29 bomber named Enola Gay, after Captain Tibbets' mother.
1945.8.6 [U. S. A.] Bombing Hiroshima with Little Boy by Paul W. Tibbets, Robert Lewis, Thomas Ferebee, William S. Parsons, Morris Jeppson, and others, at 08:16: 45. Explosion equivalent to 12.5 kilotons of TNT from 60 kg uranium235. Bomb's gross weigh was 4 tons. 140,000 civilian citizens were killed. Hibakusya (survivors) more than 300,000.Physical ailnesses due to radiation exposure, short term and long term effects.
1945. 8. 7 [U.S.S.R.] Lavrenti Pavlovich Beria was appointed to the head of Soviet atomic bomb project by Stalin.
1945.8.7 [U. S. A.] Statement by President Truman of A-bomb attack from Cruiser Augusta in Atlantic Ocean on the way back from Potsdam.
1945.8.8 [Soviet Union] Declaration of war against Japan, just after the German surrender, as promised in Yalta talk.
1945.8.8 [U. S. A.] Fat Man assembled and installed in a B-29 bomber.
1945.8.9 [Soviet Union] Attacks Japan by invasion of Manchuria.
1945.8.9 [U. S. A.] Bombing Nagasaki with Fat Man by Charles W.Sweeney, Frederick L.Ashworth, and others. Target changed from Kokura to Nagasaki because of poor visibility. 20 seconds visibility over Nagasaki. Time 11:02:00. Explosion equivalent to 22 kilotons of TNT, using 8 kg plutonium 239. Bomb's gross weight 4.5 tons. 70,000 civilian citizens were killed.
1945.8.9 [Japan] Decision accepting Potsdam Declaration at midnight meeting of ministers before Tennou Hirohito.
1945.8.10 [Japan] Sending word of acceptance of Potsdam Declaration through Switzerland, requesting Tennou's position to be kept. J. Byrnes wished to reject it, nevertheless, H. Truman accepted.
1945.8.11 [U. S. A.] Interruption of transport to Tinian of the 2nd Plutonium core and initiator by the order of G.C. Marshall. The next plutonium bomb could possibly have been dropped on August 17 or 18.
1945.8.12 [Japan] Response of U.S.A. to Japanese request.
1945.8.15 [Japan] Unconditional Surrender by Japan. The end of the World War II.
1945.8.20 [U.S.S.R.] Special Commitee on the Atomic Bomb formed. [Georgi Malenkov, Boris Vannikov, Avrami Zavenyagin, Mikhail Peruvuhin, Peter Kapitza and Igor Kurchatov]
1945.9.5 [Canada] Igor Gouzenko, a Soviet espionage, escaped from Soviet Embassy carrying 109 reports, resulting in arrest of 22 Soviet agents.
1945.9.15 [U. S. A.] Manufacturing A-bomb reported: Presented to L.Groves by major Lauris Norstad. An estimation that 204 atomic bombs are required if a hypothetical enemy is Soviet Union. The start of cold war.
1945.9.28 [U. S. A.] Scientific Panel of the Interim Committee recommends against H-bomb development. [Compton, Lawrence, Germi, Oppenheimer.]
1945.10.16 [U. S. A.] Resignation of R. Oppenheimer from Los Alamos. Replaced by Norris E. Bradbury.
1945.11.2 [U. S. A.] " A Message to Los Alamos" speech by Oppenheimer, his resignation lecture foreseeing the atomic age.
1945.11.15 Truman-Attlee-King declaration, the New Quebec agreement. A doctrine that initiative relating with the knowledge of atomic energy is kept by U.S.A., G.B. and Canada. Atomic Energy Commission in United Nations proposed.
1945.11.23 [Czechoslovakia] Soviet Union concluded a secret agreement with Czechoslovakia granting it exclusive rights to all uranium mined within country. Jachymov ores is that from which Marie Curie first extracted polonium and radium.
1945.11.24 [Japan] Cyclotrons destroyed by U.S. Army: 2 in Tokyo, 3 in Osaka and Kyoto.
1945.12.22 [England] Repatriation of German scientists to West Germany by U.S.A.
1945.12.24 [Soviet Union] Start of developing A-bomb officially notified to U.S. ambassador
1945.12 [U.S.A.] ENIAC (A computer with 18,800 vacuum tubes, 140 kw, 30 tons) ran a first rough version of the thermonuclear calculations. Los Alamos prepared a half million punched cards of data.
1946.1.25 [U.S.S.R.] Atomic bomb project decided (imitating US-model).[Stalin, Beria, Morotov, Kurchatov]
1946.3.5 [U.S.A. United Kingdom] Winston Churchill's speech of Iron Curtain at a small Protestant men's college in Fulton, Missouri. Nothing less than a call to an all-out atomic race.
1946.3.17 [U. S. A.] International Control of nuclear power proposed: Dean Gooderham Acheson. Report by R. Oppenheimer.
1946. 4. 2 [U.S.S.R.] Atomic bomb laboratory site at Sarov, 400 km east to Moskow. Soviet Los Alamos.
1946.4 [U. S. A.] First conference on development of "Super" (h-bomb). Meeting of E. Teller, E. Konopinsky, J. Manley, P. Morrison, von Neumann, S. Ulam, N. Bradberry and K. Fuchs at Los Alamos. Robert Serber opposed the development. Propose a mixture of deuterium and tritium in a cylindrical container ignited by the fireball of atomic bomb.
1946.6.14 [U. S. A.] Nuclear Control Plan by Bernard M. Baruch presented in United Nations: International control of nuclear power. It was counterattacked by a plan by Soviet Union of prohibition of manufacturing atomic bombs.
1946.6 [U. S. A.] Stockpile of nuclear weapons: 9 Fat Man bombs. Rate-limiting step is plutonium production.
1946.7.1 [U.S.A.] The Crossroads Series tests. The purpose of the tests was to examine the effects of nuclear explosions on naval vessels, planes, and animals. A fleet of surplus and captured ships anchored in the Bikini Atoll lagoon in the Marshall Islands were used as targets. The weapons used were Mk 3A ("Model 1561") Fatman-type atomic bombs, essentially unmodified from the wartime designs. Test ABLE at 22:00 30 June 1946, height of burst 160 m. Dropped by B-29 "Dave's Dream", Fell 980 ft short and 1870 ft left of target. Test BAKER at 21:35 24 July 1946, Mk 3A fission bomb (23 Kt) sub-surface test, depth of burst 27.5 m. Wall of intensely radioactive spray contaminates target fleet.
1946.12.25 [Soviet Union] Start of operation of a nuclear reactor (F-1): 100w, using 400 tons of graphite and 50 tons of uranium seized in Germany.
1946 [U.S.A.] Edward Teller invented a spherical, layered design of nuclear thermal weapon, called "Alarm Clock" (it might wake up new generation of nuclear explosives).
1946 [U.S.S.R.] "Utilization of the nuclear energy of the light elements" by I.I.Gurevich, Y.Zeldovich, I.Pomeeranchuk, Y.Khariton.
 

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