Four years after arriving in Japan, only 15-year-old Mitsuo and his mother still live in Hiroshima. His eldest brother, Toshio, is in the Japanese merchant marines. His middle brother, Tamotsu, works in a government office in Tokyo.

It's a bright, clear day. Mitsuo leaves his house around 7:30 a.m. and walks to work. He gets there about 8 a.m. He and his friends gather outside, waiting for their supervisor to give today's pep talk.

Mitsuo's mother leaves for work. Every day, she takes the same streetcar. But today she realizes she has forgotten some papers. She runs back into the house to get them. Mitsuo's mother misses her usual streetcar, and has to wait for the next one.

It's nearly 8:15 a.m. American B-29 bombers appear overhead. The sirens wail, but Mitsuo and his coworkers ignore them, as usual. The planes are headed in the direction of Tokyo. Then, for the first time ever, Mitsuo sees the planes reappear over Hiroshima. They're in position now. Looking in the sky, Mitsuo sees an object. In the instant it takes for the bomb to drop, he feels no fear, only curiosity about this thing that glistens in the sun.

Mitsuo watches the object fall behind a mountain, Mount Hiji. The exact spot where the bomb explodes is called "ground zero." Mitsuo is about two miles away, with the mountain in between. At the moment of explosion, he sees a blinding flash of light. Then the shock wave hits. Mitsuo is blown several feet into the air and knocked briefly unconscious. He awakens to see a giant mushroom cloud rising into the air. Mitsuo is a witness to the first atomic bombing in history. And Mount Hiji, which shields him from the radiation, will help him live to tell about it.

Mitsuo's mother is outside when the bomb explodes. She is about three miles from ground zero. She is not injured except for a burn on her neck. In another 20 years, cancer will develop in that spot, and she'll die from it in 1969. Still, Mitsuo's mother is luckier than the people on the street car that she missed. They all die in the blast.

The bombing of Hiroshima marked the first time a nuclear weapon was used during war. The devastating effects Mitsuo and the citizens of Hiroshima suffered were unlike anything people had experienced up to that time. Try to remember an unexpected first-time experience that overwhelmed you. Think about your reactions. Did you experience disbelief? Was it frightening? What else do you remember?

Find out why Hiroshima was chosen to be the target of the first atomic bomb drop.