The Manhattan Project and the Atomic Age (1939-1947)
The Manhattan Project was the secret US government research program that produced the first nuclear weapons during World War II. Led by Major General Leslie Groves and physicist J. Robert Oppenheimer, the project employed over 130,000 people at its peak and cost nearly 2 billion dollars. It built massive industrial complexes at Oak Ridge (Tennessee) and Hanford (Washington) to produce enriched uranium and plutonium, while the Los Alamos Laboratory in New Mexico designed and assembled the bombs. The project culminated in the Trinity test (July 16, 1945) -- the first nuclear explosion -- followed by the atomic bombings of Hiroshima (August 6) and Nagasaki (August 9) that helped end World War II. After the war, the Manhattan Project was succeeded by the civilian Atomic Energy Commission, as the world entered a new era defined by the promise and peril of atomic energy.
Events
The Einstein-Szilard Letter
Physicists Leo Szilard and Eugene Wigner draft a letter warning President Roosevelt that Nazi Germany may be developing nuclear weapons. They persuade Albert Einstein to sign it, lending the warning immense credibility. The letter urges the US to secure uranium supplies and accelerate nuclear chain reaction research.
Location: New York, New York, USA
Roosevelt Approves Uranium Research
Alexander Sachs delivers the Einstein-Szilard letter to President Roosevelt, who responds by creating the Advisory Committee on Uranium, chaired by Lyman Briggs. The initial funding is modest -- 6,000 dollars from the Navy -- but it marks the beginning of official US government interest in nuclear weapons.
Location: Washington, DC, USA
British MAUD Committee Findings
The British MAUD Committee concludes that an atomic bomb is feasible and recommends a crash program. Australian physicist Mark Oliphant travels to the US in August 1941 and discovers that the US Uranium Committee had locked the findings in a safe without acting on them. His intervention galvanizes the American scientific community.
Location: London, United Kingdom
FDR Accelerates the Program
Meeting with Vannevar Bush, President Roosevelt approves the acceleration of atomic bomb research. He establishes a Top Policy Group including himself, Vice President Wallace, Bush, Conant, Secretary of War Stimson, and Army Chief of Staff Marshall. The Army is chosen to run the project.
Location: Washington, DC, USA
The Manhattan Project Established
The Army Corps of Engineers formally establishes the Manhattan District, with Colonel James C. Marshall as its first commander. In September, Colonel Leslie Groves takes over and is promoted to Brigadier General. Groves immediately selects Oak Ridge, Tennessee, as the site for uranium enrichment facilities and begins acquiring fissile materials.
Location: Washington, DC, USA
Oppenheimer Appointed at Los Alamos
General Groves appoints physicist J. Robert Oppenheimer as director of the new secret weapons laboratory. Oppenheimer selects the remote Los Alamos mesa in New Mexico as the site. He assembles an extraordinary team of scientists including Hans Bethe, Edward Teller, Enrico Fermi, Richard Feynman, and Niels Bohr.
Location: Los Alamos, New Mexico, USA
Chicago Pile-1: First Nuclear Chain Reaction
Under the stands of Stagg Field at the University of Chicago, a team led by Enrico Fermi achieves the first artificial, self-sustaining nuclear chain reaction. The reactor -- Chicago Pile-1 -- is built from uranium and graphite bricks. Fermi controls the reaction for 28 minutes. The coded message "The Italian navigator has entered the new world" announces the success.
Location: Chicago, Illinois, USA
The Secret Cities: Oak Ridge and Hanford
Two massive secret industrial complexes rise from nothing. Oak Ridge's Clinton Engineer Works houses electromagnetic separation (Calutron) and gaseous diffusion plants to enrich uranium. Hanford Engineer Works in Washington builds three water-cooled nuclear reactors to produce plutonium. Together they employ over 100,000 workers, few of whom know what they are building.
Location: Oak Ridge, Tennessee / Hanford, Washington, USA
The Plutonium Problem
Scientists discover that plutonium produced in Hanford's reactors contains too much plutonium-240 for a simple gun-type weapon -- it would predetonate. The entire plutonium bomb program must pivot to an implosion design, which uses shaped explosive charges to compress a plutonium sphere. This demands solving extraordinarily complex problems in explosives engineering.
Location: Los Alamos, New Mexico, USA
The Trinity Test
At 5:29 AM, the first nuclear device in history -- codenamed "Gadget" -- is detonated atop a 100-foot steel tower at the Trinity site in the Jornada del Muerto desert. The explosion yields approximately 20 kilotons of TNT, creating a mushroom cloud 40,000 feet high. Oppenheimer later quotes the Bhagavad Gita: "Now I am become Death, the destroyer of worlds." The light is seen 200 miles away. The success is reported to President Truman at the Potsdam Conference.
Location: Alamogordo, New Mexico, USA
Hiroshima - "Little Boy"
The B-29 Superfortress Enola Gay, piloted by Colonel Paul Tibbets, drops "Little Boy" -- a 15-kiloton uranium gun-type bomb -- on Hiroshima at 8:15 AM. Approximately 70,000 people are killed instantly, with total deaths reaching 140,000 by the end of 1945. The city is devastated by the blast and subsequent firestorm. President Truman announces the first use of an atomic weapon, warning Japan to surrender or face "a rain of ruin from the air."
Location: Hiroshima, Japan
Nagasaki - "Fat Man"
Three days after Hiroshima, the US drops "Fat Man" -- a 21-kiloton plutonium implosion bomb -- on Nagasaki. The primary target Kokura is obscured by clouds, so the bomb is diverted to secondary target Nagasaki. About 40,000 people are killed instantly, with total deaths reaching 70,000 by year's end. Emperor Hirohito intervenes to force Japan's surrender on August 15. World War II ends.
Location: Nagasaki, Japan
Aftermath: The Atomic Energy Commission
The Manhattan Project is formally disbanded and its functions transferred to the newly created civilian Atomic Energy Commission (AEC). The AEC assumes control of nuclear weapons research, production, and oversight. The project's legacy includes the network of national laboratories, the foundation of the nuclear navy, and the dawn of the nuclear age.
Location: Washington, DC, USA