Explanation

World War II or the Second World War, was a global war that started from 1939 

The Little Boy type of bomb, was dropped on the Japanese city of Hiroshima on 6 August 1945 during World War II

The Fat Man was dropped on Nagasaki, Japan, on August 9, 1945, at 11:01 AM

the 2nd World War End on 1945

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World War I was a global war originating in Europe that lasted from 28 July 1914 to 11 November 1918.