Which country dropped atomic bombs on Japan in 1945?

The United States dropped atomic bombs on Japan in 1945. The first bomb, called Little Boy, was dropped on Hiroshima on 6 August; the second, Fat Man, was dropped on Nagasaki three days later, on 9 August.

The attacks occurred during the final weeks of World War II. The bombs had been developed through the Manhattan Project, a vast American-led research and engineering effort involving scientists and facilities in the United States, Britain, and Canada. The U.S. Army Air Forces used specially modified B-29 bombers based on Tinian, an island in the Mariana Islands.

Hiroshima was struck by the Enola Gay, piloted by Paul Tibbets. Nagasaki was attacked by Bockscar, piloted by Charles Sweeney. The bombings caused enormous destruction and killed tens of thousands immediately, with many more dying later from burns, injuries, radiation sickness, and other effects. The total death toll remains an area of historical study, partly because wartime records were incomplete.

Japan announced its surrender on 15 August 1945, after the bombings and the Soviet declaration of war against Japan. The formal surrender was signed on 2 September. The United Kingdom supported the operation through wartime agreements, but the bombs were built and deployed by the United States.