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Los Alamos Laboratory -

The Los Alamos Laboratory, codenamed Project Y, was a secret research unit established in late 1942 by the Manhattan Project for the purpose of designing and testing the first atomic bombs. Los Alamos, sited near Santa Fe in New Mexico, is today one of the largest science and technology institutions in the world.

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The Manhattan Project -

The Manhattan Project was the code name of a top secret undertaking during the Second World War that produced the first nuclear weapons. Pictured is the main gate entrance to Los Alamos, which was always heavily guarded. Image: United States Army

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Robert Oppenheimer (1904–1967) -

The wartime director of the Los Alamos Laboratory was nuclear physicist Robert Oppenheimer. He's often credited as being the "father of the atomic bomb."

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"Little Boy" -

The Manhattan Project was responsible for designing the atomic bomb of the type nicknamed "Little Boy" that was dropped by a US Army Air Force B-29 bomber on August 6, 1945 over Hiroshima, Japan. This was a gun-type fission bomb.

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"Fat Man" -

Three days later, on August 9, Nagasaki was bombed using an atomic bomb of the type nicknamed "Fat Man." This was a more sophisticated plutonium-based implosion-type device.

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Hiroshima after the bomb -

The Hiroshima bomb exploded with an energy of approximately 15 kilotons of TNT. At the moment of detonation, a fireball was generated that raised temperatures to 4,000 °C (7,232 °F ), turning the city into an inferno. Total casualties numbered 135,000, with 66,000 dead and 69,000 injured. The effects of radioactive fallout was to claim more lives over subsequent years.

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Nagasaki bombed -

Approximately 39,000 died at Nagasaki, with a further 25,000 injured. Pictured is the dense column of smoke, capped by a mushroom cloud, rising more than 18,288 m (60,000 ft) into the air over the stricken city after the explosion.

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Trinity -

The attacks on Hiroshima and Nagasaki were made possible after a test explosion conducted by the Los Alamos Laboratory, a project code named Trinity. The nuclear device used in the experiment was called the "Gadget" (pictured).

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World's first nuclear detonation -

Gadget was detonated at the Jornada del Muerto, New Mexico test site on July 16, 1945, to become the first-ever atomic bomb explosion. The successful test cleared the way for use of a nuclear device against Japan at the end of the Second World War.

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Oak Ridge, Tennessee -

Oak Ridge in Tennessee had been established in 1942 as a production site for the Manhattan Project. Secrecy was such that is was only after news of the use of the first atomic bomb against Japan was broadcast that Manhattan Project directors revealed to some of the people at Oak Ridge what they had been working on. Pictured are calutron operators at their panels in 1944. The calutrons were used to refine uranium ore into fissile material. Gladys Owens, the woman seated in the foreground, did not realize what she had been doing until seeing this photograph in a public tour of the facility 50 years later.

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Leslie Groves (1896–1970) -

Lieutenant General Leslie Richard directed the Manhattan Project and was responsible for selecting targets and test areas. Groves also oversaw the construction of the Pentagon.

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Secrecy and spies -

This is the sign that greeted employees to Oak Ridge. It reads: "WHAT YOU SEE HERE, WHAT YOU DO HERE, WHAT YOU HEAR HERE, WHEN YOU LEAVE HERE, LET IT STAY HERE." But despite the warning, one man was busily passing on nuclear secrets to the Soviet Union. Image: James E. Westcott

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Klaus Fuchs (1911–1988) -

German theoretical physicist Klaus Fuchs worked extensively on the Manhattan Project, after which he relocated to England and joined the the British atomic bomb project. In 1950, he was arrested and later admitted to spying for the USSR. Fuchs was sentenced to 14 years in prison, of which he served nine. After his release, he left for East Germany, where he died in 1988.

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Operation Crossroads -

In the immediate postwar years, the Manhattan Project conducted weapons testing at Bikini Atoll in the Marshall Islands, in the Pacific Ocean. Pictured is the iconic "Baker" explosion of July 25, 1946.

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Bikini Atoll -

Nuclear testing at Bikini Atoll consisted of the detonation of 23 nuclear weapons by the United States between 1946 and 1958. Image: NASA

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"First Lightening" -

Meanwhile, the Russians were busily catching up. This image is believed to show the aftermath of "First Lightening," the first soviet atomic bomb test on August 29, 1949, when the RDS-1 nuclear device was detonated at the Semipalatinsk test site in Kazakhstan.

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"Castle Bravo" -

"Castle Bravo" was the first in a series of high-yield thermonuclear weapon design tests conducted by the United States at Bikini Atoll as part of Operation Castle. Detonated on March 1, 1954, the device created the most powerful artificial explosion in history up to then. Image: United States Department of Energy

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Operation Redwing -

The "Cherokee" explosion of the US-led Operation Redwing—a series of 17 nuclear test detonations from May to July 1956—rises above the clouds over Bikini Atoll in the Pacific Ocean on May 20, 1956.

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"Dakota" -

Rings of vapor from the initial blast circle the mushroom cloud of "Dakota" over Bikini Atoll on June 25, 1956—another one of the frightening Operation Redwing explosions.

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Priscilla -

This is the nuclear test code named "Priscilla," carried out on June 24, 1957. The extent of the nuclear testing at Bikini Atoll led to it being declared a wasteland in the late 1950s. Seventy years later, marine life is again thriving in the vicinity, much to the surprise of scientists.

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"Tsar Bomba" -

The "Tsar Bomba," detonated by the Russians on October 30, 1961, remains the most powerful nuclear weapon ever created and tested. The explosion took place over the remote Novaya Zemlya archipelago, in the Barents Sea. The blast was 50 megatons, or equal to 50 million tons of conventional explosives. Pictured is a similar device on display at the Russian Atomic Weapon Museum at Sarov, a closed town in Nizhny Novgorod Oblast.

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Andrei Sakharov (1921–1989) -

Soviet nuclear physicist Andrei Sakharov (pictured) designed the RDS-37, the Soviet Union's first two-stage hydrogen bomb, first tested on November 22, 1955. Sakharov later experienced a crisis of conscience, becoming a staunch advocate of civil liberties and civil reforms in the Soviet Union, for which he was relentlessly persecuted. His commitment to peace, disarmament, and human rights eventually earned him the Nobel Peace Prize in 1975.

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Igor Kurchatov (1903–1960) -

Igor Kurchatov was a Soviet nuclear physicist who was the director of the Soviet atomic bomb project. He oversaw the "First Lightening" test in 1949 and along with Georgy Flyorov (1913–1990) and Andrei Sakharov is regarded as the "father of the Soviet atomic bomb."

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Cuban Missile Crisis -

The Cuban Missile Crisis of October 1962—effectively a dangerous test of brinkmanship between the United States and the Soviet Union during the Cold War—has gone down in history as the moment when the two superpowers came closest to nuclear conflict.

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Operation Hurricane -

The United Kingdom's first nuclear test took place on October 3, 1952 in the Montebello Islands in Western Australia as part of Operation Hurricane. Great Britain subsequently became the third country to develop a nuclear arsenal. Image: Naval Historical Collection

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Gerboise Bleue -

On February 13, 1960, France conducted its first nuclear test, codenamed Gerboise Bleue ("Blue Jerboa") in southern Algeria. General Pierre Marie Gallois was instrumental in the endeavor, seen here at Paris Invalides on March 10, 1960 receiving the Legion of Honor from French President Charles de Gaulle.

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Mururoa -

France controversially continued to test its nuclear capability in the southern Pacific Ocean at Mururoa Atoll, also known as Aopuni. From 1966 until 1996, this was the country's testing ground for 193 bombs, which detonated first atmospheric then underground devices.

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China -

The first nuclear weapons test conducted by the People's Republic of China took place on October 16, 1964. The device was detonated in a remote part of central Asia, along the Lob Nor Lake in the Takala Makan Desert. With the test, China became the fifth nuclear power in the world and the first Asian nation to possess a nuclear capability.

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India -

A huge crater marks the site of the first Indian underground nuclear test, conducted on May 18, 1974 at Pokhran in the desert state of Rajasthan.

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Pakistan -

India's traditional rival Pakistan caught up with its neighbor on May 28, 1998, when it conducted five simultaneous underground nuclear tests at Ras Koh Hills (pictured) in the Chagai District of Balochistan province. A second test, Chagai-II, took place on May 30.

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North Korea -

North Korea is the only country in the world that still tests nuclear weapons. The first test was conducted in 2006. Since then, Pyongyang has carried out a further six tests, in 2009, 2013, twice in 2016, once in 2017, and in 2022. As tensions between North Korea and the US continue to rise, the country continues to develop its arsenal of nuclear-capable weapons. 

Sources: (US History) (Biography) (Comprehensive Nuclear Test Ban Treaty Organization) (Atomic Heritage Foundation) (Britannica) (The Guardian) (The New York Times) 

See also: The world's most powerful nuclear nations

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