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The Soviet Union denies it, but in the fall, President Harry Truman tells the American public that the Soviets tested their first nuclear device, officially starting the arms race. "We do not advise Americans that doomsday is near and that they can expect atomic bombs to start falling on their heads a month or year from now," the Bulletin explains. "But we think they have reason to be deeply alarmed and to be prepared for grave decisions." Read the full statement.