Following the attack on Pearl Harbor on December 7, 1941 Americans were on edge.
There were unsubstantiated reports days later that aircraft were approaching New York City and some panicked in fear of an invasion. Though no such event occurred, it was enough to cause a temporary tumble in the stock market.
Those nerves were shared on the west coast where mistakenly identified things like fishing nets and whales were thought to be warships from Japan.
These tensions were not only fueled by what had happened at Pearl Harbor in Hawaii. A real Japanese submarine surfaced outside Santa Barbara and launched artillery shells at an oil field there. Though it caused little damage and no deaths, it did represent Japan's willingness to risk an attack on mainland United States.
The attack that seemed to serve no real purpose perhaps achieved exactly what it was meant to. Californians were anxious about a full-scale attack. The following day, February 24, 1942, naval intelligence warned navy units near the coast of California to be on alert and ready for an attack from Japan.
The paranoia came to a head in the early hours of February 25. At around 2:00 AM, radar men believed they spotted an enemy vessel over 100 miles west of Los Angeles.
Radars picked up an unidentified target 120 miles west of Los Angeles. Antiaircraft batteries were alerted at 2:15 am and were put on Green Alert—ready to fire—a few minutes later. (William Goss)
Sirens wailed as an ordered blackout darkened the city. Spotlights began searching the night sky as soldiers stood ready behind anti-aircraft guns. After another nervous hour passed, events culminated as the first shots were fired.
A report of a UFO led to the guns being unleashed into the night sky. Over 1,400 rounds were launched into the darkness toward the possibly imagined Japanese aerial attack.
...even though the mysterious object tracked in from sea seems to have vanished. At 2:43 am, planes were reported near Long Beach, and a few minutes later a coast artillery colonel spotted ‘about 25 planes at 12,000 feet’ over Los Angeles. At 3:06 am a balloon carrying a red flare was seen over Santa Monica and four batteries of anti-aircraft artillery opened fire, whereupon ‘the air over Los Angeles erupted like a volcano. (William Goss)
Newspaper headlines told of the air battle over Los Angeles with varied reports on what happened as civilians reported seeing Japanese war planes flying overhead in formation.
Navy Secretary Frank Knox said "As far as I know, the whole raid was a false alarm and could be contributed to jittery nerves," while Secretary of War Henry Stimson believed some attack was attempted, likely to damage civilian morale.
The only casualties were civilian deaths as two had heart attacks during the chaotic event and three others died in panicked car accidents.
What the military fired upon in those night skies, if anything at all, remains a mystery.