THE DEADLY RACE

How the road to peace led to an arms contest between the USA and USSR, with prototypes, proliferation and the world’s biggest bomb

Within days of the Nagasaki bombing, some of the scientists who'd worked on the Manhattan Project released a statement. In it, they warned of the "grave danger that lies ahead", predicting that other countries might now be "spurred on to create atomic bombs of their own in self-defense [leading to] an armaments race".

The arms race they were predicting, however, had already started. As soon as Soviet leader Joseph Stalin had seen evidence of the destruction at Hiroshima, he'd issued orders for the USSR to develop an atomic weapon. Despite the immense secrecy around the Manhattan Project, the Soviets were better positioned to do this than the Americans imagined. For over a year, they'd not only known of the laboratory at Las Alamos, but they'd also had two spies working there as scientists.

America's nuclear monopoly ended on 29 August 1949 when the USSR tested its first atomic bomb at Semipalatinsk in Kazakhstan. Shocked, but determined to stay ahead of their Cold War rivals, the US now looked to develop a weapon even more powerful than an atomic bomb. Edward Teller, a physicist at Los Alamos, championed the idea of hydrogen fusion. Harness the same energy the Sun uses, he argued, and you could produce a weapon with catastrophic power. In January 1950, President Harry Truman announced that the US would build what was now being called a hydrogen (or H) bomb.