On the night of February 24-25, 1942, barely three months after Pearl Harbor and one day after a Japanese submarine shelled an oil refinery near Santa Barbara, air raid sirens wailed across Los Angeles. Anti-aircraft batteries opened fire, pumping 1,400 rounds of ammunition into the sky over the city for over an hour.
Searchlights swept the darkness. Newspapers reported swarms of enemy aircraft. Blackout regulations were enforced. Over a million people watched the spectacle from their homes and streets. Five civilians died—three from car accidents during the blackout and two from heart attacks triggered by the stress. Falling shell fragments damaged buildings and cars across the city.
The next day, investigations concluded there had been no enemy aircraft over Los Angeles. The targets were likely weather balloons, which had triggered the already-extreme wartime jitters. The incident, dubbed the "Battle of Los Angeles," remains a famous example of war hysteria. It has since become fodder for UFO conspiracy theorists, though the most likely explanation remains a combination of weather balloons, war nerves, and the chaos of a cascading false alarm.