What were the atomic bombs?
Answer
Weapons dropped on Hiroshima and Nagasaki
Explanation
The atomic bombs were nuclear weapons that the United States developed during World War II and dropped on the Japanese cities of Hiroshima on August 6, 1945 and Nagasaki on August 9, 1945, hastening Japan's surrender and ending the war. The weapons were the result of the Manhattan Project, a secret program authorized by President Franklin D. Roosevelt in 1942 after Albert Einstein and other scientists warned him that Nazi Germany might develop atomic weapons. The project was led by Brigadier General Leslie Groves of the United States Army Corps of Engineers, with physicist J. Robert Oppenheimer directing the scientific laboratory at Los Alamos, New Mexico.
Other major sites included Oak Ridge, Tennessee for uranium enrichment and Hanford, Washington for plutonium production. At its peak, the project employed roughly 130,000 workers and cost about 2 billion dollars in 1940s money. The first test bomb, code-named Trinity, was detonated at the Alamogordo bombing range in New Mexico on July 16, 1945, releasing energy equal to roughly 21,000 tons of TNT.
Two operational bombs followed. The first bomb, named Little Boy, used uranium-235 and a gun-type design. It was dropped from the B-29 bomber Enola Gay, piloted by Colonel Paul Tibbets, on Hiroshima at 8:15 a.m. local time on August 6, 1945, exploding about 1,900 feet above the Shima Surgical Clinic with a yield of about 15 kilotons. The explosion and resulting firestorm destroyed roughly five square miles of the city and killed an estimated 80,000 people instantly, with the death toll rising to 140,000 by year's end from burns, injuries, and radiation sickness.
The second bomb, named Fat Man, used plutonium-239 and an implosion design. It was dropped from the B-29 Bockscar, piloted by Major Charles Sweeney, on Nagasaki at 11:02 a.m. on August 9, 1945, exploding with a yield of about 21 kilotons. About 40,000 died instantly and 70,000 by the end of 1945. Emperor Hirohito announced Japan's surrender on August 15.
The atomic bombs are the only nuclear weapons ever used in war, and their use began the nuclear age, the postwar arms race, and continuing debates about nuclear ethics, deterrence, and disarmament.
Why this matters for your test
USCIS uses this question to confirm applicants know the events that ended World War II and started the nuclear age. Knowing about Hiroshima and Nagasaki helps explain American Cold War policy and the international effort to prevent nuclear proliferation today.
Source: USCIS 128 Civics Questions (2025)
