Timeline
1938 – “March: Germany invades Austria.
November: The Nazis attack
Jews in Germany and Austria, destroying their homes and businesses.
1939 – January: Lise Meitner and Otto Frisch identify fission in uranium atoms.
August: Two scientists, Leo Szilard and Eugene Wigner, write to President Roosevelt, explaining
that powerful new weapon might be possible.
September: Germany invades Poland; Great Britain and France declare war on Germany.
October: President Roosevelt orders a committee to investigate the possibility of developing atomic weapons.
1940 – April: Germany invades Norway and Denmark.
May: Germany invades Netherlands and Belgium.
June: German troops enter Paris.
September: Japan joins the Axis Powers.
1941 – February: A group of scientists working at the University of California discover another element
that will fission: plutonium.
December: Japan attacks the United States at Pearl Harbor, Hawaii; The United States and Great
Britain declare war on Japan; Germany and Italy declare war on the United States.
1942 – June: President Roosevelt orders the army to build an atomic bomb.
September: General Leslie Groves purchases land in Tennessee to build a factory to produce fuel
for an atomic bomb.
October: Los Alamos, New Mexico, is selected as the site for the bomb-designing laboratory.
December: Enrico Fermi creates the first self-sustaining chain reaction in uranium at the laboratory in Chicago.
1943 – January: The Los Alamos Laboratory opens; J. Robert Oppenheimer becomes its director;
Groves buys a site in Hanford, Washington, for a fuel factory.
September: Italy surrenders to the Allies.
1944 – June: The Allies invade France.
August: Paris is liberated; Groves chooses a site in southern New Mexico for the implosion test.
September: Belgium is liberated.
1945 – March: Allied troops enter German concentration camps to find that the Nazis have been murdering
millions of European Jews; United States forces liberate the Philippines and the island of Iwo Jima.
April: President Roosevelt dies, making Vice President Harry Truman the new president; Truman
learns about the Manhattan Project; Hitler commits suicide.
May: Germany surrenders.
June: United States troops capture Okinawa.
July 16: The implosion bomb is successfully tested at Trinity.
July 26: The Potsdam Declaration is issued by the Allies, demanding Japan’s unconditional surrender.
July 28: Japan rejects the Potsdam Declaration.
August 6: Atomic bomb is dropped on Hiroshima, Japan.
August 8: The Soviet Union declares war on Japan.
August 9: Second atomic bomb is dropped on Nagasaki, Japan.
August 14: World War II ends.
September 2: Japan surrenders formally.
1946 – The Cold War begins.
1947 – January: The Manhattan Engineering District officially ends; The Atomic Energy Commission
is formed to oversee atomic energy and nuclear weapons.
1949 – The Soviet Union develops its own atomic weapon, marking the beginning of the nuclear arms race.
1952 – The United States successfully tests the hydrogen bomb.
1957 – The first United States nuclear power plant opens in Pennsylvania.
1970 – The United States and the Soviet Union agree to limit the number and kind of nuclear weapons
they make; The specific agreement is worked out in negotiations called the Strategic Arms
Limitation Talks.
1980 – 1990 – The United States and the Soviet Union agree to begin reducing their nuclear stockpiles,
according to the Strategic Arms Reduction Talks treaty.
1991 – The Cold War ends.”
Timeline taken from:Gonzales, Doreen. The Manhattan Project and the Atomic Bomb. Berkeley Heights, NJ: Enslow Publishers Inc., 2000. Print.
November: The Nazis attack
Jews in Germany and Austria, destroying their homes and businesses.
1939 – January: Lise Meitner and Otto Frisch identify fission in uranium atoms.
August: Two scientists, Leo Szilard and Eugene Wigner, write to President Roosevelt, explaining
that powerful new weapon might be possible.
September: Germany invades Poland; Great Britain and France declare war on Germany.
October: President Roosevelt orders a committee to investigate the possibility of developing atomic weapons.
1940 – April: Germany invades Norway and Denmark.
May: Germany invades Netherlands and Belgium.
June: German troops enter Paris.
September: Japan joins the Axis Powers.
1941 – February: A group of scientists working at the University of California discover another element
that will fission: plutonium.
December: Japan attacks the United States at Pearl Harbor, Hawaii; The United States and Great
Britain declare war on Japan; Germany and Italy declare war on the United States.
1942 – June: President Roosevelt orders the army to build an atomic bomb.
September: General Leslie Groves purchases land in Tennessee to build a factory to produce fuel
for an atomic bomb.
October: Los Alamos, New Mexico, is selected as the site for the bomb-designing laboratory.
December: Enrico Fermi creates the first self-sustaining chain reaction in uranium at the laboratory in Chicago.
1943 – January: The Los Alamos Laboratory opens; J. Robert Oppenheimer becomes its director;
Groves buys a site in Hanford, Washington, for a fuel factory.
September: Italy surrenders to the Allies.
1944 – June: The Allies invade France.
August: Paris is liberated; Groves chooses a site in southern New Mexico for the implosion test.
September: Belgium is liberated.
1945 – March: Allied troops enter German concentration camps to find that the Nazis have been murdering
millions of European Jews; United States forces liberate the Philippines and the island of Iwo Jima.
April: President Roosevelt dies, making Vice President Harry Truman the new president; Truman
learns about the Manhattan Project; Hitler commits suicide.
May: Germany surrenders.
June: United States troops capture Okinawa.
July 16: The implosion bomb is successfully tested at Trinity.
July 26: The Potsdam Declaration is issued by the Allies, demanding Japan’s unconditional surrender.
July 28: Japan rejects the Potsdam Declaration.
August 6: Atomic bomb is dropped on Hiroshima, Japan.
August 8: The Soviet Union declares war on Japan.
August 9: Second atomic bomb is dropped on Nagasaki, Japan.
August 14: World War II ends.
September 2: Japan surrenders formally.
1946 – The Cold War begins.
1947 – January: The Manhattan Engineering District officially ends; The Atomic Energy Commission
is formed to oversee atomic energy and nuclear weapons.
1949 – The Soviet Union develops its own atomic weapon, marking the beginning of the nuclear arms race.
1952 – The United States successfully tests the hydrogen bomb.
1957 – The first United States nuclear power plant opens in Pennsylvania.
1970 – The United States and the Soviet Union agree to limit the number and kind of nuclear weapons
they make; The specific agreement is worked out in negotiations called the Strategic Arms
Limitation Talks.
1980 – 1990 – The United States and the Soviet Union agree to begin reducing their nuclear stockpiles,
according to the Strategic Arms Reduction Talks treaty.
1991 – The Cold War ends.”
Timeline taken from:Gonzales, Doreen. The Manhattan Project and the Atomic Bomb. Berkeley Heights, NJ: Enslow Publishers Inc., 2000. Print.