Hiroshima anniversary

The Atomic Bomb Dome is silhouetted at sunset in Hiroshima, western Japan,  Monday, Aug. 5, 2013. Hiroshima marks the 68th anniversary of the world's first atomic bombing Tuesday.

Shizuo Kambayashi/AP

The Atomic Bomb Dome is silhouetted at sunset in Hiroshima, western Japan, on Monday, eve of the 68th anniversary of the world’s first use of nuclear weapons in war