The first atom bomb destroyed Hiroshima on 6 August 1945. Just three days later, a second atom bomb flattened the city of Nagasaki, even though Japan had long been ready to capitulate. Conventional wisdom holds that these two atomic explosions - the only use of nuclear bombs in the history of war - brought the Second World War to an end. Yet an increasing number of historians are critical of this interpretation. International experts say it is a myth and say it glorifies an war crime that killed more than 100 thousand civilians. Historian Tsuyoshi Hasegawa argues that the Soviet Union’s unexpected declaration of war on Japan is what really pushed Tokyo to surrender. He says that Japan had been hoping that Moscow would step in to broker a diplomatic end to the conflict. Research in Russian archives has discovered that the United States knew that, so why did it drop the bombs at all? Especially the second one?