A boy floats a candle lit paper lantern on the river in front of the Atomic Bomb Dome during 70th anniversary activities, commemorating the atomic bombing of Hiroshima, Japan, at the Hiroshima Peace Memorial Park on Aug. 6, 2015. Chris McGrath/Getty Images
The events of the mid-20th century shook the world and shattered the optimism that came with the end of the “war to end all wars” and the economic boom of the 1920s.