This article provides an overview of the perils of U.S. and Soviet nuclear war planning during the Cold War. In particular, the article discusses instances of false alarms, when one side or the other picked up indications of an imminent attack by the other side and had to take measures to determine whether the indicators were accurate. None of these incidents posed a large danger of an accidental nuclear war, but they illustrate the inherent risks of the war preparations that both the United States and the Soviet Union took for their immense nuclear arsenals.