The United States dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki in August 1945, during the final stage of the Second World War.The two bombings, which killed at least 129,000 people, remain the only use of nuclear weapons for warfare in history.merican President Harry S. Truman called for Japan's surrender 16 hours later, warning them to expect a rain of ruin from the air, the like of which has never been seen on this earth.. Three days later, on August 9, the U.S. dropped a plutonium implosion-type bomb (Fat Man) on the city of Nagasaki.