Hiroshima was bombed on 6th August 1945 at 8.16 am. It is estimated that 80,000 people died then, with another 60,000 dying from injuries and radiation sickness in the following months for a death-toll of around 140,000, from a population of somewhere over 250,000. This doesn't count the tens of thousands who died later from cancer and other effects of exposure to radiation.
The testimony of a survivor brings home the meaning of the statistics:
The appearance of people was . . . well, they all had skin blackened by burns. . . . They had no hair because their hair was burned, and at a glance you couldn't tell whether you were looking at them from in front or in back. . . . They held their arms bent [forward] like this . . . and their skin - not only on their hands, but on their faces and bodies too - hung down. . . . If there had been only one or two such people . . . perhaps I would not have had such a strong impression. But wherever I walked I met these people. . . . Many of them died along the road - I can still picture them in my mind - like walking ghosts. (A survivor quoted in Robert Jay Lifton, Death in Life: Survivors of Hiroshima (New York: Random House, 1967) 27 - see this page on About.com
The destruction of Nagasaki followed on 9th August at 11.02am. (Nagasaki was the second-choice target. Kokura city, the intended target, was spared because of thick cloud cover when the US planes arrived there earlier that morning.) It is estimated that 75,000 people died in the attack, with another 25,000 dying from radiation sickness in the next few months. This gives a death-toll of around 100,000 from a population of approximately 240,000. Again, this doesn't count the people who died from cancers and other effects of exposure to radiation.
Fujie Urata Matsumoto, a survivor of the attack on Nagasaki, is quoted on the page on About.com:
The pumpkin field in front of the house was blown clean. Nothing was left of the whole thick crop, except that in place of the pumpkins there was a woman's head. I looked at the face to see if I knew her. It was a woman of about forty. She must have been from another part of town - I had never seen her around here. A gold tooth gleamed in the wide-open mouth. A handful of singed hair hung down from the left temple over her cheek, dangling in her mouth. Her eyelids were drawn up, showing black holes where the eyes had been burned out. . . . She had probably looked square into the flash and gotten her eyeballs burned.
(Fujie Urata Matsumoto as quoted in Takashi Nagai, We of Nagasaki: The Story of Survivors in an Atomic Wasteland (New York: Duell, Sloan and Pearce, 1964) 42.)
For more information see this Wikipedia article. There are more links on this page.
It is widely agreed by historians that the war could have been concluded without the destruction of Hiroshima or Nagasaki. There are a number of explanations of the bombings, including the desire of the US administration for an unconditional surrender and their fear that the USSR would enter the war and take territory in North-East Asia if negotiations between Japan and the US took long. Other motivations may have played a role: a desire to demonstrate the atomic bomb as a first strike in the cold war, or as a test of the effect of an atom bomb on a city.
As evidence for the last point, consider this analysis from the page previously referred to on About.com, quoting Dan Kurzman's Day of the Bomb:
There had been four cities chosen as possible targets: Hiroshima, Kokura, Nagasaki, and Niigata (Kyoto was the first choice until it was removed from the list by Secretary of War Henry L. Stimson). The cities were chosen because they had been otherwise relatively untouched during the war. The Target Committee wanted the first bomb to be "sufficiently spectacular for the importance of the weapon to be internationally recognized when publicity on it was released."
The Hiroshima city government and the Nagaski city government campaign against nuclear weapons. A Kyodo article covers the activities this month of two of the major anti-nuclear organisations in Japan, the Japan Congress Against A- and H-Bombs (Gensuikin) and the Japan Council against A & H Bombs (Gensuikyo).
The Japan Congress Against A- and H-Bombs (Gensuikin) hosted an annual international meeting, attended by guest speakers, including experts on nuclear issues on the Korean Peninsula, U.S. nuclear policies and the Japan-North Korea relationship.
''Unlike Iraq, North Korea is (geopolitically) surrounded by strong countries. It is the North Korean leaders themselves who feel threatened the most by other countries in the area,'' Lee Jong Wong, a professor at Rikkyo University (St. Paul's University) in Tokyo, told an audience of some 100 people.
''Nuclear development is a reasonable choice for North Korea to maintain its prestige domestically and people's support to the current regime,'' Lee said, adding that nuclear policies could also be an obstacle to the reconstruction of the North's state system. ''Comprehensive dialogues with other countries would be a way out.''
The Tokyo conference, as part of the World Congress Against A- and H-Bombs, will be followed by various events -- public debates and peace classes for children -- in Hiroshima from Wednesday to Friday and in Nagasaki on Aug. 7 and 9, Gensuikin officials said.
Another major antinuclear group, the Japan Council against A & H Bombs, known in Japanese as Gensuikyo, will start a series of rallies -- the World Conference against A & H Bombs -- Monday in Hiroshima, where a peace memorial ceremony will be held Friday.
Gensuikyo's events in Hiroshima will continue through Friday and then move to Nagasaki for rallies on Aug. 8 and 9.
Public pressure in Japan is the principal reason, in my opinion, why it has no nuclear weapons. Its right-wing government signed the Non-Proliferation Treaty, reluctantly, in 1970, but only ratified it six years later after the US agreed "not to interfere with Tokyo's pursuit of independent reprocessing capabilities in its civilian nuclear programme." (Selig Harrison, Korean Endgame, p. 233) This, together with Japan's highly-advanced space programme, is a carefully judged means of keeping inter-continental nuclear missiles within Japan's capabilities in a matter of months.
The nuclear powers in the region are the US, China, and Russia. China has offered the US a no-first use agreement on nuclear weapons repeatedly, and the US has repeatedly refused the offer, reserving the 'right' to use nuclear weapons first in a conflict if the other side uses chemical or biological weapons, or perhaps even in the case of large-scale conventional warfare. This stance is a primary reason for North Korea's attempts to develop nuclear weapons and missiles to carry them. South Korea has also worked on isotope-enrichment and missile technology, worried about its nuclear-capable neighbours and North Korea, but mostly interested in having a deterrent if Japan goes nuclear.
Tensions in the region rose in 2000-1 when President Clinton abandoned plans for a summit with Kim Jong-Il in Pyongyang, were exacerbated by the incoming Bush administration's attitude to negotiations with North Korea and have been in crisis since Bush's inclusion of North Korea in his 'axis of evil' in January 2001.
Plans for a nuclear-free North East Asia have been on the table since the end of the cold war and may well be achievable. The key is a US approach to negotiations which treats the North Korean government as a negotiating partner and works towards concessions on both sides. The current US attitude - that North Korea has sinned and must repent and atone - is leading towards disaster.