Timeline Description: While scientists began making key discoveries in X-rays and radioactivity beginning in the 1890s, it was not until the 1930s that science made crucial advances towards developing nuclear weapons. When World War II broke out in 1939, the United States devoted its energies to developing an atomic bomb. The weapons were put to devastating use in Japan, but after the war, the U.S. and the USSR launched the nuclear arms race out of mistrust. Major powers gradually reversed nuclear proliferation, but to this day some countries continue to develop and test immensely powerful weapons.
|March 1934||Enrico Fermi creates the world's first nuclear fission.
Building on studies of artificial radioactivity, Enrico Fermi creates the world's first nuclear fission by irradiating uranium with neutrons. He believes he has produced the first element beyond uranium, but it is not until 1938 that two separate teams prove he actually discovered nuclear fission, a key process in atomic weaponry.
|March 15, 1943||The Manhattan Project begins work in Los Alamos, New Mexico.
Concerned that the Germans may be developing an atomic weapon, the United States government funds a program known as the Manhattan Project, with J. Robert Oppenheimer as Scientific Director. The project's goal is to develop an atomic weapon before the Germans do. On March 15, 1943, Oppenheimer moves the work to a secret laboratory in Los Alamos, New Mexico, to begin serious development.
|July 16, 1945||The first plutonium bomb is tested.
On July 16, 1945, the Manhattan Project successfully tests the first plutonium bomb near Alamogordo, New Mexico. Its creators are stunned by its immense power, and although Germany has surrendered, U.S. President Harry S. Truman insists on using the bomb to convince Japan to surrender.
|August 1945||The first atomic bombs are dropped in Japan.
Hoping to force Japan to surrender, the U.S. drops an atomic bomb with the equivalent force of 12.5 kilotons of TNT on Hiroshima, Japan, on August 6, 1945. 70,000 citizens are killed instantly, and another 70,000 die of illnesses and injuries caused by the bomb. The U.S. then drops another bomb on Nagasaki, Japan, on August 9, though fewer people die instantly. Japan surrenders, thus ending World War II. However, Japanese citizens continue to succumb to the effects of the bombs, and by 1950, approximately 54% of the population has died.
|August 29, 1949||The USSR successfully tests an atomic weapon.
After the disasters at Hiroshima and Nagasaki, major powers declare publicly that they hope to place the atomic bomb under international control. However, mistrust between the United States and the USSR leads both countries to continue developing their nuclear programs, thus launching the nuclear arms race. On August 29, 1949, the USSR successfully tests its first atomic weapon, using their knowledge of the American bomb used at Nagasaki.
|October 3, 1952||The United Kingdom successfully tests an atomic weapon.
During World War II, the United Kingdom launches its own nuclear weapons program in cooperation with the United States. The UK successfully tests its first atomic weapon on October 3, 1952, making it the third country to join the nuclear age.
|November 1, 1952||The first hydrogen bomb is successfully tested.
Hoping to develop an even more powerful weapon than the USSR, the U.S. pursues thermonuclear weapons. The first hydrogen bomb, "Mike," is successfully tested at Enewetak Atoll in the Pacific Ocean on November 1, 1952. Its explosion is the equivalent of 10 million tons of TNT. The USSR quickly follows suit and develops its own hydrogen bomb.
|February 13, 1960||France successfully tests an atomic weapon.
While France receives little technological and scientific support from other countries to develop its own nuclear program, it successfully tests its first atomic weapon on February 13, 1960. France becomes the fourth country to join the nuclear age.
|October 30, 1961||The USSR creates the most powerful explosion with its latest test.
On October 30, 1961, the USSR creates the most powerful explosion with its test of a "monster bomb" at Novaya Zemlya. The bomb's explosion is equivalent to 50 megatons of TNT, with more destructive power than all the bombs and explosives deployed during World War II, including the three atomic weapons.
|October 16, 1962||The Cuban Missile Crisis begins.
When the U.S. discovers Soviet nuclear missiles in Cuba, a tense standoff, later known as the Cuban Missile Crisis, begins between the two superpowers. The U.S. blockades Cuba from October 16 to October 29, 1962, and the U.S. and the Soviet Union come to the brink of nuclear war.
|October 16, 1964||China successfully tests an atomic weapon.
The USSR reluctantly helps China with its nuclear weapons program, and on October 16, 1964, China successfully tests an atomic weapon. With this test, China becomes the fifth nuclear power in the world.
|July 1, 1968||The Nuclear Non-Proliferation Treaty is signed.
Fearing the continued proliferation of nuclear weapons, the United States and the Soviet Union agree to prohibit the spread of further nuclear weapons, while allowing the use of peaceful nuclear energy. Their agreement, the Nuclear Non-Proliferation Treaty, opens for signature on July 1, 1968. When it goes into effect in 1970, the United States, the United Kingdom, and the Soviet Union, along with 59 non-nuclear countries, have signed on.
|September 24, 1996||The Comprehensive Nuclear Test Ban Treaty opens for signatures.
On September 24, 1996, the Comprehensive Nuclear Test Ban Treaty opens for signatures at the United Nations. The US, the UK, China, Russia, and France all sign and agree to prohibit nuclear explosive testing, in the countries' continued attempt to decrease nuclear proliferation. This builds on the Partial Test Ban Treaty of 1963 and the 1968 Nuclear Non-Proliferation Treaty.
|May 1998||India and Pakistan test nuclear weapons.
India conducts three nuclear tests in May 1998, including one of a thermonuclear weapon. This is India's second round of testing, following its first round in 1974. Later in May, Pakistan tests six weapons, including uranium and plutonium bombs, in response to India's tests.
|October 9, 2006||North Korea successfully tests a nuclear weapon.
On October 9, 2006, North Korea becomes the eighth country to successfully test a nuclear weapon, after withdrawing from the Nuclear Non-Proliferation Treaty. Countries around the world condemn North Korea's nuclear proliferation, and the country eventually announces it will suspend development. However, North Korea continues to develop and test weapons.