The United States wanted to both minimize casualties among its troops and to establish its global supremacy following the Second World War, which is why they wanted to make Japan surrender as early as possible. This is why they needed to inflict enough damage that the Japanese government and citizens lost the will to fight. Starting in spring 1945, the United States began studying possible targets for the bomb, taking into account the size of the city, its military and industrial importance, and whether any key military command bases were there. Of the candidate cities, Hiroshima was the only one which was believed to have no Allied prisoner-of-war camps, so it was selected as the primary target.
Scientific research has been carried out to determine exactly where the atomic bomb that was dropped over Hiroshima exploded (ground zero). According to the most reliable report, the bomb exploded at a point roughly 600 meters above ground at what is now Otemachi Carpark No. 3 on the south side of Shima Hospital, located at 5-24 1-chome, Ote-machi. This is 160 meters southeast of the Atomic Bomb Dome (the then Industrial Promotion Hall). With this single explosion, almost every building in the city was destroyed, burned to the ground.
The Atomic Bomb Dome is about 160 meters northwest of ground zero, meaning it was exposed to the blast at quite close range. Everyone inside died instantly due to the tremendous blast and heat, and the huge amount of heat caused the building to burn to the ground. The roof, which took the impact of the blast almost vertically, was destroyed, but as the blast was vertical, the surrounding walls were not pushed over completely, but were miraculously spared from destruction.
There was a debate after the war about whether to leave the Atomic Bomb Dome or to demolish it. There were people then who wanted to demolish it because it reminded them of the tragedy of the bombing. It is generally understood, however, that the preservation movement got its impetus from the diary of Hiroko Kajiyama, who was exposed to the bomb at age 1 and died of leukemia at age 16. She wrote "Only that ravaged Industrial Promotion Hall will be there to tell the world forever how fearsome atomic bombs are." This led to the preservation movement getting its start. Using donations, construction work began in 1972 on preserving the structure, allowing the building to survive to this day.
The Hiroshima Peace Memorial Museum provides talks by survivors and others who help to pass on what it would have been like, allowing people to gain an understanding of what happened then. The Hiroshima National Peace Memorial Hall for the Atomic Bomb Victims also regularly holds readings by volunteers of records written by those affected or poems about the atomic bombing.