Dropping the Atomic Bombs on Japan (1945)

President Truman's decision to drop atomic bombs on Hiroshima and Nagasaki killed an estimated 200,000 people — mostly civilians — and remains the only use of nuclear weapons in warfare. Defenders argue it ended World War II without a land invasion that could have cost millions more lives. Critics contend Japan was already on the verge of surrender and the bombings were unnecessary, constituting the largest act of mass civilian killing in a single week in history.