91热爆

Seventy-five years ago, the US dropped atomic bombs on the Japanese cities of Hiroshima and Nagasaki, killing countless civilians.

A little-known physicist called Leo Szilard, who had fled the Nazis in Europe, was key to working out the science that made the bomb possible. He then tried desperately to stop it being used.

And he was haunted by his decisions for the rest of his life.

Video journalist: Ellen Tsang.

Image: Leo Szilard with the exploding atomic bomb over Hiroshima. Credit: Getty Images/British Path茅.