The race to build the bomb


From 1937 to 1945 scientists in five countries – Japan, Germany, the United States, Britain and the Soviet Union – were pursuing the quest to split the atom and build the bomb

Japan invades China. Ultranationalist military leaders justify plan to occupy China, Manchuria and Korea under pretext of Hakko Ichiu – ancient Shinto concept of “all the world under one roof”, ruled by Japan’s divine Emperor. Invasion sets Japan on course for World War Two

German scientists Otto Hahn and Fritz Strassman demonstrate nuclear fission – splitting the nucleus of a uranium atom and converting some of its mass to energy. Japanese atom bomb project begins under direction of physicist Yoshio Nishina. Japan purchases cyclotron – to enrich uranium – from University of California

Germany starts project to build atom bomb. Rival teams led by physicists Kurt Diebner and Werner Heisenberg explore uranium and plutonium devices

Scientists led by Albert Einstein write to U.S. President Franklin D. Roosevelt, warning of Nazi Germany’s A-bomb project. Letter recommends that U.S. develops its own atom bomb – Manhattan Project is born


Adolf Hitler invades Poland. Britain and France declare war on Germany. Britain begins GEN75 project to build atom bomb

Heisenberg’s protégé, Carl Friedrich Freiherr von Weizsäcke, proposes use of eka-rhenium as nuclear explosive. Eka rhenium – now called neptunium – decays into plutonium

Heisenberg’s team files patent for plutonium bomb in Germany

Dec 7:
Japan attacks Pearl Harbour, bringing U.S. into war

Soviet leader Joseph Stalin learns of U.S. and German A-bomb projects. Soviet atomic weapons programme begins under leadership of physicist Igor Kurchatov.

In U.S., Manhattan Project employs almost 129,000 people – including British and Canadian atom scientists – under leadership of Robert Oppenheimer


1945, Apr 1:
U.S. invades Okinawa – last stepping stone on road to Japan – 81-day battle claims more than 110,000 Japanese and 14,000 American lives. U.S. firebombing of Japanese cities forces Tokyo’s A-bomb project to be moved to Hungnam, in what is now North Korea

Apr 12:
Roosevelt dies, Harry S. Truman becomes U.S. president. Briefed on Manhattan Project, Truman sees bomb as way to end war quickly and save American lives

May 7:
Allied armies accept unconditional surrender of Nazi Germany – Pacific war continues

Jun 18:
Truman approves plan to invade and occupy Japan. Invasion will employ 2.7 million U.S. troops

Two atomic bombs – uranium-fuelled Little Boy and plutonium-fuelled Fat Man – are transported to Tinian in the U.S.-occupied Marianas

Jul 16, Trinity Test:
After $2 billion of research ($26.3bn in current value), prototype plutonium device is detonated in New Mexico desert. It yields four times more energy than scientists had thought possible. Oppenheimer quotes Hindu Bhagavad Gita: “I am become Death, the destroyer of worlds”

Jul 26, Potsdam Declaration:
U.S., Britain and China demand that Japan surrender or face “prompt and utter destruction”. Japan ignores declaration

Aug 6, 8:15am:
B-29 bomber Enola Gay, flying at 9,150 metres, drops atomic bomb on Hiroshima, killing almost everyone within 1,000m of ground zero

Aug 9, 11:02am:
U.S. drops plutonium bomb on Nagasaki, killing 40,000 people instantly

Aug 14:
Japan surrenders

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