Atomic bombings of Hiroshima and Nagasaki

Hiroshima is the capital of Hiroshima Prefecture, and the largest city in the Chūgoku region of western Honshu, the largest island of Japan.... It became best known as the first city in history to be destroyed by a nuclear weapon when the United States Army Air Forces dropped an atomic bomb on it at 8:15 A.M. on August 6, 1945, near the end of World War II. Hiroshima gained city status on April 1, 1889. On April 1, 1980, Hiroshima became a designated city. The city's current mayor since April 2011 is Kazumi Matsui. Hiroshima was founded on the river delta coastline of the Seto Inland Sea in 1589 by the powerful warlord Mōri Terumoto, who made it his capital after leaving Koriyama Castle in Aki Province. Hiroshima Castle was quickly built, and Terumoto moved in in 1593. Terumoto was on the losing side at the Battle of Sekigahara. The winner, Tokugawa Ieyasu, deprived Mori Terumoto of most of his fiefs including Hiroshima and gave Aki province to Masanori Fukushima, a daimyo who had supported Tokugawa. The castle passed to Asano Nagaakira in 1619, and Asano was appointed the daimyo of this area.
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World War II, or the Second World War , was a global conflict that was underway by 1939 and ended in 1945. It involved most of the world's... nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis. It was the most widespread war in history, with more than 100 million military personnel mobilised. In a state of "total war", the major participants placed their entire economic, industrial, and scientific capabilities at the service of the war effort, erasing the distinction between civilian and military resources. Marked by significant events involving the mass death of civilians, including the Holocaust and the only use of nuclear weapons in warfare, it is the deadliest conflict in human history, resulting in 50 million to over 70 million fatalities. Although Japan was already at war with China in 1937, the world war is generally said to have begun on 1 September 1939, with the invasion of Poland by Germany, and subsequent declarations of war on Germany by France and most of the countries of the British Empire and Commonwealth. Germany set out to establish a large empire in Europe.
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The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that... produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army Corps of Engineers. The Army component of the project was designated the Manhattan District; "Manhattan" gradually superseded the official codename, "Development of Substitute Materials", for the entire project. Along the way, the Manhattan Project absorbed its earlier British counterpart, Tube Alloys. The Manhattan Project began modestly in 1939, but grew to employ more than 130,000 people and cost nearly US$2 billion . Over 90% of the cost was for building factories and producing the fissionable materials, with less than 10% for development and production of the weapons. Research and production took place at more than 30 sites, some secret, across the United States, the United Kingdom and Canada. Two types of atomic bomb were developed during the war.
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