Atomic bombing of Hiroshima

The United States’ atomic attack on Hiroshima, Japan, on August 6, 1945, killed tens of thousands immediately and left many more exposed to burns and radiation.

Little Boy: The uranium gun-type fission bomb detonated over Hiroshima on August 6, 1945. This was the weapon whose blast and radiation struck Hiroshima.
Manhattan Project: The United States-led wartime program that developed the first nuclear weapons. Its scientists and industrial teams built the bomb used against Hiroshima.
Hiroshima: A Japanese city on the Seto Inland Sea, largely destroyed by an atomic bomb in 1945. The city’s destruction and subsequent rebuilding define the bombing’s local legacy.
Operation Downfall: The Allied plan for a possible invasion of the Japanese home islands in 1945. It represented the invasion alternative cited in arguments defending the bombings.
Enola Gay: A Boeing B-29 Superfortress that carried the Hiroshima bomb from Tinian. Its crew released Little Boy over the city.
Trinity test: The first detonation of a nuclear weapon, conducted in New Mexico on July 16, 1945. The successful test preceded the Hiroshima mission by three weeks.
Atomic bombing of Nagasaki: The United States’ atomic attack on Nagasaki on August 9, 1945. The second bombing followed Hiroshima three days later and intensified pressure on Japan.
Strategic bombing: The use of air power to attack an enemy’s industrial, military, or civilian infrastructure. Hiroshima was an unprecedented nuclear instance of attacks on cities from the air.
Nuclear fission: The splitting of atomic nuclei, which releases energy and additional neutrons. Little Boy’s explosive energy came from a rapidly multiplying uranium fission chain reaction.
Harry S. Truman: The 33rd president of the United States, who authorized the use of atomic bombs against Japan. Truman approved the decision that led to the Hiroshima attack.

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