Atom bomb: On 6 and 9

On 6 and 9 August 1945, the United States detonated two atomic bombs over the Japanese cities of Hiroshima and Nagasaki, respectively, during World War II. The aerial bombings killed 150,000 to 246,000 people, most of whom were civilians, and remain the only uses of nuclear weapons in an armed conflict. Japan announced its surrender to the Allies on 15 August, six days after the bombing of Nagasaki and the Soviet Union's declaration of war against Japan and invasion of Manchuria. The ... At their core, nuclear weapons are devices designed to release an enormous amount of energy through nuclear reactions, either by splitting atoms (fission) or combining them (fusion). This article takes readers through the fascinating and sobering history of the development of the nuclear bomb, beginning with the early discoveries in nuclear physics, through the intense efforts of the Manhattan Project, and finally to the bomb’s devastating use in Hiroshima and Nagasaki. A nuclear weapon is a device designed to release energy in an explosive manner as a result of nuclear fission, nuclear fusion, or a combination of the two. Fission weapons are commonly referred to as atomic bombs, and fusion weapons are referred to as thermonuclear bombs or, more commonly, hydrogen bombs.