On 6 August 1945, the first of the only two atomic bombs ever used in warfare exploded 1,900 feet above Hiroshima. The sudden drop in air pressure squeezed people’s eyeballs out of their sockets. Ground temperature reached 4,000°C, over twice the temperature at which iron melts. Tens of thousands of human beings were ‘burned, decapitated, disemboweled, crushed and irradiated’. The detonation of the ‘gadget’ – as the scientists who built the bomb called it – above one of the city’s main hospitals killed all the patients, nurses and doctors there. Three days later a plutonium bomb, almost twice as powerful as the one dropped on Hiroshima, exploded 1,640 feet above Nagasaki, leaving a vast white scar and killing 39,000 people, far fewer than the 78,000 dead at Hiroshima. The blast streaked through the sewers of the Shiroyama National Elementary School, killing 1,400 of its 1,500 pupils. Nagasaki’s entire medical system ‘ceased to exist’. Eight and a half thousand schoolchildren were killed. All the geisha houses and brothels were wiped out, but 94 per cent of the city’s industrial workers survived.

In both cities, as Paul Ham shows in his comprehensive and horrifying account, people continued to die for years afterwards from radiation sickness, while others were permanently disfigured by ghastly burns. After reports of these lasting effects began to leak out – American censors obscured them for at least a