Smokey Atomic Bomb
The Race to Build the Bomb

Atom Bomb Timeline
On December 6, 1941 the United States Government committed $2 billion dollars to the Manhattan Project to build a secret bomb. At that time, only a few scientists around the globe believed it was theoretically possible. In four short years it became a reality and was a significant factor in bringing an end to World War II.

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Harold UreyHarold C. Urey discovers deuterium (heavy hydrogen) which is present (0.014%) in all natural hydrogen compounds including water. Later contributes to U235 isotope separation.


James ChadwickJames Chadwick proves the existence of neutrons. Not being repelled by similarly-charged particles, the neutron made an ideal "bullet" for bombarding other nuclei.

January 30, 1933

Adolf HitlerAdolf Hitler becomes chancellor of Germany. Due to anti-semitism, many prominent scientists flee central Europe. They felt Hilter's Germany would create the bomb first.

September 12, 1933

Leo SzilardHungarian physicist Leo Szilard realizes that, "if we could find an element which is split by neutrons, and which would emit two neutrons when it absorbs one, such an element could sustain a nuclear chain reaction."


Enrico FermiEnrico Fermi of Italy irradiates uranium with neutrons. He believes he has produced the first transuranic element, but unknowingly achieves the world's first nuclear fission.

June 28 and July 4, 1934

Leo SzilardLeo Szilard files a patent application for the atomic bomb. The patent described the concept of using neutron induced chain reactions to create explosions.

December 19, 1938

Otto HahnOtto Hahn, Fritz Strassman and Lise Meitner produce Uranium nuclear fission at Germany's Kaiser Wilhelm Institute.

August 2, 1939

Albert EinsteinAlbert Einstein's first letter to President Franklin Roosevelt. The letter, originally drafted by Leo Szilard states "that the element uranium may be turned into a new and important source of energy in the immediate future."

September 1, 1939

WWII BeginsWith "Operation Weiss", Germany invades Poland and World War II begins. American papers call it a Blitzkrieg or "lightening war" because of the speed and efficiency of the attack.


E.O. LawrenceThe University of California begins building a giant cyclotron under the direction of Ernest O. Lawrence.

December 6, 1941

RooseveltThe day before the bombing of Pearl Harbor, President Roosevelt authorizes the Manhattan Engineering District with $2 billion to build the atom bomb.

September 23, 1942

Col. Groves & OppenheimerColonel Leslie Groves is promoted to Brigadier-General and put in charge of the Manhattan Project. He recruits J. Robert Oppenheimer as Scientific Director.

December 2, 1942

Enrico FermiAt the University of Chicago, in a squash court under Stagg Field, Enrico Fermi and his team produce the world's first controlled and self-sustained nuclear fission reaction.

November 29, 1943

Winston ChurchillThe US Military begin remodeling the B-29 bomber for the delivery of the A-bomb. Bomb's sizes are decided: "Thin Man" representing Roosevelt and "Fat Boy" for Churchill.

July 17, 1944

Port ChicagoImportant military port in the San Francisco Bay goes up in a horrific explosion killing 323 men, disintegrating two ships and an entire train. Calculations and declassified documents lead to a possible US test firing of a nuclear weapon.

April 12, 1945

Franklin RooseveltFranklin Roosevelt dies, and Harry S. Truman becomes the 33rd President of the United States. April 25th, Truman is briefed about the Manhattan Project and the development of the bomb.

May 7, 1945

Nazi's SurrenderSoon after Adolf Hitler killed himself, German General Alfred Johl signed the unconditional surrender of all German forces on all fronts, ending tWorld War II for Europe.

June 14, 1945

OppenheimerThe Franck Committee Report - with its request that the bomb be demonstrated to Japan before being used on civilians - is taken to Fermi, Lawrence and Oppenheimer.

July 16, 1945

TrinityTrinity Test at Alamogordo, New Mexico: exploding with a 18,000 Ton TNT equivalence.

August 6 & 9, 1945

Little BoyLittle Boy explodes over Hiroshima killing over 100,000 people. Three days later, Fat Man explodes over Nagasaki killing 75,000. Japan surrenders soon after.

  More about Urey   More about Chadwick   More on the Nuremberg Laws   More on Leo Szilard   More on Enrico Fermi   More on Atomic Bomb Patent   More on Hahn and Fission   The letters to FDR from Einstein   More on the start of WWII   More on E.O. Lawrence   More on FDR's Role   More on General Groves   The Chicago Pile       The Last Wave from Port Chicago   More on Harry S. Truman   The unconditional surrender of Germany - Real Audio   Franck Committee Report   Quicktime Movie of Test   Truman's August 9th speech re Hiroshima