September 1983: the Soviet early-warning system “Oko”, cutting-edge, extremely trusted, reports an American nuclear missile inbound. Then five more. Everyone in the bunker looks at lieutenant colonel Stanislav Petrov; superiors order the response. And he says no. He reasoned a real US first strike wouldn’t be six missiles, and bet the world on it being a sensor error. It was: sunlight reflecting off clouds. He was quietly pushed aside rather than decorated, you can’t punish the man who saved the world, but you can’t reward him for disobeying either. He died modest and mostly unknown. One word, no, and here we all are.