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. 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 ... Explore the complete history of nuclear bomb — from scientific discovery and World War II to global arms race, treaties, and present-day nuclear powers. On August 6, 1945, during World War II (1939-45), an American B-29 bomber dropped the world’s first deployed atomic bomb over the Japanese city of Hiroshima. The explosion immediately killed an...
