Atomic Bombs on Japan

Setting the scene

The United States dropped atomic bombs on Hiroshima on August 6, 1945, and Nagasaki on August 9, 1945, the only use of nuclear weapons in war. The bombs were developed by the Manhattan Project, a secret $2 billion program employing 130,000 people. President Truman, who learned of the bomb after Roosevelt's death, authorized its use to force Japan's surrender and avoid a costly invasion, which planners estimated could cost 250,000-500,000 American lives.

What happened

The Hiroshima bomb, 'Little Boy' (uranium), exploded at 8:15 a.m. at 1,900 feet, with a yield of 15 kilotons, destroying 5 square miles and killing 70,000-80,000 instantly, with total deaths reaching 140,000 by year's end. The Nagasaki bomb, 'Fat Man' (plutonium), exploded at 11:02 a.m. on August 9, killing 40,000 instantly and 70,000 total. Both cities were chosen as relatively undamaged targets to demonstrate the bomb's power. Japan surrendered on August 15, after the Soviet invasion of Manchuria on August 9.

Why it still matters

The atomic bombings remain the most controversial decision in American history. Defenders argue they ended the war quickly, saving lives on both sides, and were justified by Japanese atrocities and refusal to surrender. Critics argue Japan was already defeated and would have surrendered without invasion, making the bombings unnecessary and immoral, particularly the second bomb on Nagasaki. The bombings began the nuclear age and Cold War arms race. They demonstrated humanity's capacity for self-destruction and created the taboo against nuclear use that has held since 1945. The bombings are commemorated annually in Japan as a call for nuclear abolition.

Background

Japan surrendered, ending World War II.