Stanislav Petrov, a lieutenant-colonel in the military intelligence section of the Soviet Union's secret service, reluctantly eased himself into the commander's seat in the underground early warning bunker south of Moscow. It should have been his night off but another officer had gone sick and he had been summoned at the last minute. Before him were screens showing photographs of underground missile silos in the Midwest prairies of America, relayed from spy satellites in the sky. He and his men watched and listened on headphones for any sign of movement - anything unusual that might suggest the U.S. was launching...