The atomic bombings of Hiroshima and Nagasaki were nuclear attacks during World War II against the Empire of Japan by the United States of America under US President Harry S. Truman. On August 6, 1945, the nuclear weapon "Little Boy" was dropped on the city of Hiroshima, followed on August 9, 1945 by the detonation of the "Fat Man" nuclear bomb over Nagasaki. These are the only uses of nuclear weapons in warfare.



Several factors make it difficult to estimate casualty numbers due to the bombings. The population prior to the bombings is only roughly known, because of formal and informal evacuations, and unknown numbers of forced laborers. Some victims were burned beyond recognition or their bodies disposed in mass cremations.Records of military personnel were destroyed, and entire families perished, leaving nobody to report the casualties. According to most estimates, the bombing of Hiroshima killed approximately 70,000 people due to immediate effects of the blast. Estimates of total deaths by the end of 1945 range from 90,000 to 140,000, due to burns, radiation, and subsequent disease, aggravated by lack of medical resources.Some estimates state up to 200,000 may have died by 1950, due to cancer and other long-term effects.The numbers for Nagasaki are consistently lower, because the valley terrain reduced the impact of the bomb, with immediate deaths estimates ranging from 40,000 to 75,000.In both cities, the overwhelming majority of the deaths were civilians.The role of the bombings in Japan's surrender, as well as the effects and justification of them, has been subject to much debate.



On August 15, 1945 Japan announced its surrender to the Allied Powers, signing the Instrument of Surrender on September 2 which officially ended World War II. Furthermore, the experience of bombing led post-war Japan to adopt Three Non-Nuclear Principles, which forbids Japan from nuclear armament.