The 200,000 casualties caused by the bombings were caused by many reasons. The majority of the people killed were civilians.
"Within the first two to four months of the bombings, the acute effects killed 90,000–166,000 people in Hiroshima and 60,000–80,000 in Nagasaki,[1] with roughly half of the deaths in each city occurring on the first day. The Hiroshima prefectural health department estimates that, of the people who died on the day of the explosion, 60% died from flash or flame burns, 30% from falling debris and 10% from other causes. During the following months, large numbers died from the effect of burns, radiation sickness, and other injuries, compounded by illness. In a US estimate of the total immediate and short term cause of death, 15–20% died from radiation sickness, 20–30% from flash burns, and 50–60% from other injuries, compounded by illness.[5] In both cities, most of the dead were civilians..."
This excerpt, taken from Wikipedia, describes the devastation that the atomic bombs caused and it shows a demographic for each type of injury.
Informational video about the dropping of the "Little Boy" on Hiroshima and the planes that did it.
"I had finished breakfast and was getting ready to go to the newspaper when it happened. There was a flash from the indoor wires as if lightening had struck. I didn't hear any sound, how shall I say, the world around me turned bright white. And I was momentarily blinded as if a magnesium light had lit up in front of my eyes. Immediately after that, the blast came. I was bare from the waist up, and the blast was so intense, it felt like hundreds of needles were stabling me all at once. The blast grew large holes in the walls of the first and second floor. I could barely see the room because of all the dirt. I pulled my camera and the clothes issued by the military headquarters out from under the mound of the debris, and I got dressed. I thought I would go to either either the newspaper or to the headquarters. That was about 40 minutes after the blast..."
Yoshito Matsushige was a 32 year old cameraman for the Chugoku Newspaper at that time. He was at his home in Midori-cho, 2.7kilometers from the hypocenter when the A-bomb was dropped. He walked around the city right after the bombing and took five photographs which have become important historical documents.
Accounts of the American justification for dropping a second bomb in Nagasaki.
"I was in my office. I had just entered the room and said "Good morning." to colleagues and I was about to approach my desk when outside it suddenly turned bright red. I felt very hot on my cheeks. Being the chief of the room, I shouted to the young men and women in the room that they should
evacuate. As soon as I cried, I felt weightless as if I were an astronaut. I was then unconscious for 20 or 30 seconds. When I came to, I realized that everybody including myself was lying at
one side of the room. Nobody was standing. The desks and chairs had also blown off to one side. At the windows, there was no window glass and the window frames had been blown out as well. I
went to the windows to find out where the bombing had taken place. And I saw the mushroom cloud over the gas company. The sound and shock somehow suggested that the bomb had been dropped
right over the gas company. I still had no idea what had happened..."
An interview by a worker that describes the initial impact of the atomic bomb in Hiroshima.
