Operation Crossroads
There were only seven nuclear bombs in existence in July 1946. The two bombs used in the test were Fat Man plutonium implosion-type nuclear weapons of the kind dropped on Nagasaki. The "Able" bomb was stenciled with the name "Gilda" and decorated with an "Esquire" magazine photograph of Rita Hayworth, star of the 1946 movie, "Gilda". The "Baker" bomb was "Helen of Bikini." This femme-fatale theme for nuclear weapons, combining seduction and destruction, is epitomized by the use in all languages, starting in 1946, of "bikini" as the name for a woman's two-piece bathing suit.
Hiroshima Peace Memorial
Earlier, on 25 July, General Carl Spaatz, commander of the United States Strategic Air Forces in the Pacific, received orders to deliver a "special bomb" attack on selected cities in Japan. The first target city chosen was Hiroshima, which had an important port on southern Honshu and was headquarters of the Japanese Second General Army with 40,000 military personnel in the city. The bomb was assembled in secret and loaded on the "Enola Gay". It consisted of a uranium isotope 235 core shielded by hundreds of kilograms of lead. The bomb, code named "Little Boy", possessed a force equivalent to 15,000 tons of TNT. The plane dropped Little Boy over the city at 8:15:17 a.m. local time on 6 August 1945. Within 43 seconds of being dropped, it detonated over the city, missing its target by . Intended for the Aioi Bridge, the bomb instead exploded directly over the Shima Hospital, which was very near to the Genbaku Dome. Because the explosion was almost directly overhead, the building was able to retain its shape. The building's vertical columns were able to resist the nearly vertical downward force of the blast, and parts of the concrete and brick outer walls remained intact. The center of the blast occurred horizontally and vertically from the Dome. Everyone inside the building was killed instantly.