Today we begin a series of special reports to mark the 70th anniversary of the end of World War Two. In this week in 1945 the US dropped atomic bombs on Hiroshima and Nagasaki. Not many people know about the practice runs before the atomic attacks, when American air crews dropped stand-ins for the real thing. Survivors and a team of researchers are working to tell people about these lethal rehearsals and the damage they caused.

Tomomi Hashimoto begins our series, "The War, 70 Years On," with this special report on the so-called "pumpkin bombs."

American writer John Hersey's description of the aftermath of the atomic bombing of Hiroshima was a sensation when it came out in 1946. His grandson, Cannon Hersey has been digging into the archives to learn more. He is also turning his talents to the story of Hiroshima, and taking up where his grandfather left off.