On August 6, 1945, at 8:15 in the morning, the American B-29 bomber Enola Gay dropped an atomic bomb over the center of the city of Hiroshima, Japan. Hiroshima was the first target ever attacked with nuclear weapons in the history of the world.

The bomb exploded about 200 yards over the city, creating a 13 kiloton explosion, a fireball, a shock-wave, and a burst of radiation. On the day that the bomb was dropped, there were about 255,000 people living in Hiroshima.

The explosion completely incinerated everything within a one mile radius of the city center. The shock-wave and the fires ignited by the explosion damaged or completely destroyed about nine-tenths of the buildings in the city. Somewhere between 70,000 and 80,000 people—that is, about one third of the entire population of the city—died immediately. The heat of the explosion vaporized or burned alive many of those closest to ground zero. Others were killed by the force of the shock-wave or crushed under collapsing buildings. Many more died from acute radiation poisoning—that is, from the effects of having their internal organs burned away in the intense radiation from the blast. …