Atomic bombings of Hiroshima and Nagasaki
By August 1945, the Allies' Manhattan Project had produced two types of atomic bombs, and the 509th Composite Group of the United States Army Air Forces (USAAF) was equipped with the specialized Silverplate version of the Boeing B-29 Superfortress that could deliver them from Tinian in the Mariana Islands. Orders for atomic bombs to be used on four Japanese cities were issued on July 25. On August 6, one of the modified B-29s dropped a uranium gun-type bomb codenamed "Little Boy" on Hiroshima. Three days later, on August 9, a plutonium implosion-type bomb codenamed "Fat Man" was dropped by another B-29 on Nagasaki. The bombs immediately devastated their targets. Over the next two to four months, the acute effects of the atomic bombings killed 90,000–146,000 people in Hiroshima and 39,000–80,000 people in Nagasaki; roughly half of the deaths in each city occurred on the first day. Large numbers of people continued to die from the effects of burns, radiation sickness, and other injuries, compounded by illness and malnutrition, for many months afterward. In both cities, most of the dead were civilians, although Hiroshima had a sizable military garrison.
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.