On August 6, 1945, the United States used its massive, atomic weapon against Hiroshima, Japan.

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On August 6, 1945, the United States used its massive, atomic weapon against Hiroshima, Japan.

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Thousands gathered at a peace memorial park in Hiroshima on Tuesday, 6th August, 2013 to mark the 68th anniversary of the US atomic bombing of the Japanese city. (Getty Images/Buddhika Weerasinghe)

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A woman burns incenses and pray in front of a monument for atomic bomb victims at the Hiroshima Peace Memorial Park on the day of the 68th anniversary of the atomic bombing of Hiroshima on August 6, 2013 in Hiroshima, Japan. (Getty Images/Buddhika Weerasinghe)

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An American B-29 bomber named Enola Gay dropped an atomic bomb on August 6, 1945, in one of the final chapters of World War II. It killed an estimated 140,000 by December that year. Three days later, the port city of Nagasaki was also bombed. (Getty Images)

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