Bombing of Hiroshima and Nagasa

On August 6, 1945, during World War II (1939-45), an American B-29 bomber dropped the world’s first deployed atomic bomb over the Japanese city of Hiroshima. The explosion wiped out 90 percent of the city and immediately killed 80,000 people; tens of thousands more would later die of radiation exposure. Three days later, a second B-29 dropped another A-bomb on Nagasaki, killing an estimated 40,000 people. Japan's Emperor Hirohito announced his country's unconditional surrender in WWII in a radio address on August 15, citing the devastating power of "a new and most cruel bomb."

At the time of its bombing, Hiroshima was a city of both industrial and military significance. A number of military units were located nearby, the most important of which was the headquarters of Field Marshal Shunroku Hata's Second General Army, which commanded the defense of all of southern Japan, and was located in Hiroshima Castle. Hata's command consisted of some 400,000 men, most of whom were on Kyushu where an Allied invasion was correctly anticipated. Also present in Hiroshima were the headquarters of the 59th Army, the 5th Division and the 224th Division, a recently formed mobile unit. The city was defended by five batteries of 7-cm and 8-cm (2.8 and 3.1 inch) anti-aircraft guns of the 3rd Anti-Aircraft Division, including units from the 121st and 122nd Anti-Aircraft Regiments and the 22nd and 45th Separate Anti-Aircraft Battalions. In total, an estimated 40,000 Japanese military personnel were stationed in the city.

Hiroshima was a minor supply and logistics base for the Japanese military, but it also had large stockpiles of military supplies. The city was also a communications center, a key port for shipping and an assembly area for troops. It was a beehive of war industry, manufacturing parts for planes and boats, for bombs, rifles, and handguns; children were shown how to construct and hurl gasoline bombs and the wheelchair-bound and bedridden were assembling booby traps to be planted in the beaches of Kyushu. A new slogan appeared on the walls of Hiroshima: "FORGET SELF! ALL OUT FOR YOUR COUNTRY!" It was also the second largest city in Japan after Kyoto that was still undamaged by air raids, due to the fact that it lacked the aircraft manufacturing industry that was the XXI Bomber Command's priority target. On July 3, the Joint Chiefs of Staff placed it off limits to bombers, along with Kokura, Niigata and Kyoto.

The center of the city contained several reinforced concrete buildings and lighter structures. Outside the center, the area was congested by a dense collection of small timber-made workshops set among Japanese houses. A few larger industrial plants lay near the outskirts of the city. The houses were constructed of timber with tile roofs, and many of the industrial buildings were also built around timber frames. The city as a whole was highly susceptible to fire damage.

The population of Hiroshima had reached a peak of over 381,000 earlier in the war but prior to the atomic bombing, the population had steadily decreased because of a systematic evacuation ordered by the Japanese government. At the time of the attack, the population was approximately 340,000–350,000. Residents wondered why Hiroshima had been spared destruction by firebombing. Some speculated that the city was to be saved for U.S. occupation headquarters, others thought perhaps their relatives in Hawaii and California had petitioned the U.S. government to avoid bombing Hiroshima. More realistic city officials had ordered buildings torn down to create long, straight firebreaks, beginning in 1944. Firebreaks continued to be expanded and extended up to the morning of August 6, 1945.