When the atomic bomb was dropped, Nagasaki had a population of about 240,000. However, by the end of December 1945, 73,884 of its people had been killed, and 74,909 had been injured by the A-bomb. In addition, so-called “atomic bomb disease,” caused by the heat rays, blast and radiation, afflicted the survivors, many of whom developed various diseases with the passing of time. Some A-bomb victims are still suffering from these diseases.
The houses damaged by the atomic bomb totaled 18,409, approximately 36% of all houses in Nagasaki City.
(The above figures are based on estimates up to the end of December 1945, from a report released in July 1950 by the Committee for the Preservation of Atomic Bomb Artifacts.

When the atomic bomb exploded, a fireball approximately 280 m in diameter was created. Its surface temperature was as high as that of the sun.
Near the hypocenter, all the burnable things were ignited.
Exposed to the heat, victims’ skin burned, the injuries later turning into running sores. Some people’s bodies were burned to cinder. A-bomb burns were inconceivably worse than ordinary burns.

The A-bomb blast had tremendous force, which flattened or blew away buildings. Many people were crushed to death under the collapsed buildings. From broken windows, countless splinters of glass showered upon people. Moreover, fires started and spreaded due to the heat rays and blast.

The primary difference between atomic bombs and conventional bombs is that the atomic bombs emit radiation. Although A-bomb radiation is not visible or tangible, it enters the human body and destroys various cells, causing the malfunction of various organs and body parts, which result in disease. Many persons, even though not apparently injured, died of exposure to radiation. People were injured not only by the radiation released when the atomic bomb exploded, but also by the radioactive fallout, or "ashes of death" (radioactive particles that fall to earth following a nuclear explosion), and what is called “black rain” which contains such fallout.

In the area close to the hypocenter, buildings were destroyed by the blast and fires caused by the atomic bomb, killing or severely injuring many people. Notably, the Nagasaki Medical College, located about 500 meters from the hypocenter, was seriously damaged. The College was the most adequately equipped medical institute in Nagasaki City at that time. In response to the call for help, many rescue and relief teams came to Nagasaki from other parts of Nagasaki Prefecture, as well as from various parts of Kyushu. National schools (now primary schools) functioned as aid stations for the many injured persons who were brought there. Meanwhile, relief trains transported the injured to the Isahaya and Omura districts. Despite these efforts, however, fatalities increased
because there were so many injured that surviving doctors and nurses could not provide sufficient treatment, and because of the lack of medical supplies. Even under such circumstances, self-sacrificing relief activities continued.