Atomic Bomb Timeline

German troops occupy Norway, seizing the world's only heavy-water production plant at Vemork.

Frisch and Rudolf Peierls submit a memorandum to the British government estimating the critical mass of uranium 235 needed for an atomic bomb and urging a bomb research project.

German scientists fail to observe neutron multiplication in the reactor i n Hamburg.

Using the Berkeley cyclotron, Philip Abelson and Edwin McMillan demonstrate that neutrons captured by uranium 238 lead to the creation of elements 93 and 94, neptunium and plutonium.

Based on experiments with a natural uranium reactor, the Germans reject graphite as a moderator.

Glenn Seaborg discovers new element (atomic number 94), which they call plutonium.

American physicists confirm that plutonium is fissionable, thus usable for a bomb.

British 'MAUD' Committee reports that a weapon could be made with 22 pounds of pure uranium 235.

President Roosevelt authorizes the Manhattan Engineering District. The secret U.S. project to build an atomic bomb, later to be called the Manhattan Project, is put under the direction of the Office of Scientific Research and Development.

Brigadier General Leslie Groves is put in charge of the Manhattan Project. He recruits J. Robert Oppenheimer as Scientific Director.

Construction of a uranium isotope separation plant begins at Oak Ridge, Tennessee.

Enrico Fermi at the University of Chicago produces the world's first controlled and sustained nuclear fission reaction.

Planning begins for construction of reactors at Hanford, Washington, to breed plutonium for a bomb.

Oppenheimer moves the bomb development to a secret laboratory located at Los Alamos, New Mexico.

Bohr presents his memorandum on intentional control of nuclear weapons to Roosevelt.

First batch of spent fuel obtained from Hanford reactors.

The ALSOS mission obtains documents implying that the German's rate of progress toward a bomb had diminished.

First plutonium reprocessing begins at Hanford.

First uranium 235 separated at Oak Ridge, Tennessee.

The Franck Report is sent to Secretary of War Stimson.

U.S. explodes the world's first atomic bomb, the Trinity test, at Alamogordo, New Mexico.

Little Boy, an uranium bomb, was dropped on Hiroshima, Japan. Between 80,000 - 140,000 people are killed.

Fat Man, a plutonium bomb, was dropped on Nagasaki, Japan. About 74,000 people are killed.

Bernard Baruch presents the Acheson-Lilienthal plan to internationalize the atomic energy. It is rejected by the U.S.S.R.

First subsurface detonation by U.S. is achieved at Bikini Atoll in the Pacific.

Demonstrations are held in Times Square, New York, against nuclear testing.

President Harry S. Truman signs the Atomic Energy Act. Its purpose is to control the development and production of nuclear weapons and to direct the research and development of peaceful uses of nuclear energy.

The Soviet Union achieves its first nuclear chain reaction in Moscow.

Atomic Energy Commission (AEC) takes over nuclear weapons program from the Army.

The United Kingdom authorizes the development of nuclear weapons.

Under the direction of William Penney, the UK begins design of its plutonium bomb.

The United Kingdom builds its first atomic reactor.

NATO established.

Soviet Union detonates its first atomic bomb, Joe 1, at Semipalatinsk in Kazakhstan. It is a copy of the Fat Man bomb and has a yield of 21 kilotons.

General Advisory Committee of the AEC recommends that the more powerful atomic bombs should be built rather than hydrogen bombs.

Germany, Italy, and Japan sign the Tripartite Pact creating the Axis Alliance.

Germany and the Axis Powers attack Russia with a huge force of over four million troops.

The Japanese attack the US Navy in Pearl Harbor. The next day the US enters World War II on the side of the Allies.

The US Navy defeats the Japanese navy at the Battle of Midway, first defeat in 350 years.

D-day and the Normandy invasion. Allied forces invade France and push back the Germans.

US President Franklin Roosevelt dies. He is succeeded by President Harry Truman.

Adolf Hitler commits suicide as he knows Germany has lost the war.

Germany surrenders to the allies.

Japan surrenders to US general Douglass MacArthur and the Allies.

Americans declared neutrality in the European war, due to skepticim of the Allied propaganda.

Japan and Russia sign a neutrality.

The US extends aid to the Soviet Union.

Germany and Italy declare war on the US.

As more than 40,000 Japanese troops come ashore north of Manila, American general Douglas MacArthur orders a retreat to Bataan.

U.S. War and Navy Departments announce that commanders of the forces in Hawaii at the time of the Pearl Harbor attack will be court-martialed for dereliction of duty.

In the first American raid on the Japanese mainland, 16 B-25 carrier-launched bombers led by Lt. Col. James Doolittle strike Tokyo, Kobe, Yokohama, Nagoya and Yokosuka.

A Japanese submarine shells the military depot at Fort Stevens, Oregon in the first attack on the U.S. mainland.

US wins at Battle of the Bismarck Sea and forces Japanese to add submarines.

US P-38 Lightning pilot intercepts the bomber carrying Japanese Admiral Isoroku Yamamoto and shot it down.

Japanese launch last and largest Banzai charge into American Lines.

Americans attack Japanese installations in Manila.

Americans attack Japanese in Manila.

American fire bombers come to Japanese Cities and hundreds of Napalm bombs were dropped over multiple days.

Japanese sign ceremonial surrender terms aboard the USS Missouri.

U.S. conducts atomic tests at Eniwetok Atoll.