As strange, serious and scary as the erroneous emergency notification Saturday about a missile attack against Hawaii may have been, it was far from the first such false alarm the country has faced.

Every decade since the dawn of the nuclear age has seen its share of close calls, experts said. During the Cold War, the government routinely dealt with hundreds of anomalies that could have led to a nuclear launch.

But it is rare for a false alert about an impending missile attack to actually reach the public, said Garrett M. Graff, who has written about the extensive preparations made to allow the government to continue in the event of a nuclear or terrorist attack.

Mr. Graff, the author of “Raven Rock: The Story of the U.S. Government’s Secret Plan to Save Itself — While the Rest of Us Die,” said in a phone interview that the alert on Saturday, coming at a time of heightened tensions with North Korea, was “pretty unprecedented.”