The Battle of Los Angeles
An anti-aircraft barrage over Los Angeles on the night of February 24 to 25, 1942, fired at a rumored Japanese air raid. Five civilians died during the night.
Wikipedia describes the Battle of Los Angeles, also called the Great Los Angeles Air Raid, as a rumored Japanese attack and the barrage that followed. The Army Air Forces' wartime history, quoted by the California State Military Museum, says radar showed an unknown target about 120 miles west of the city early on the 25th, and that gun batteries went on alert at 0215, ready to fire within minutes. The air force kept its fighters on the ground.
Brian Dunning, on the Skeptoid podcast in 2009, says the guns fired 1,430 rounds over nearly an hour, dropping tons of shrapnel on the city, eight and a half by his count. He says many people saw nothing, while others described balloons or airplanes, and CBS Radio described a blimp. With the moon down and the city blacked out, the searchlights lit only smoke from the shell bursts. Smithsonian Magazine puts the count at over 1,400 rounds, says none hit an enemy plane because there were none, and calls a stray weather balloon the likeliest cause of the radar contact.
Smithsonian Magazine counts five casualties, from road accidents during the blackout and from shock-induced heart attacks, and Wikipedia records that five civilians died. The Los Angeles Times, reprinting its 1942 coverage in 2017, reported shells that failed to burst in the air exploding on the ground, wrecking a garage and a patio and bursting the tire of a car parked nearby.
"The Battle of Los Angeles, also known as the Great Los Angeles Air Raid, is the name given by contemporary sources to a rumored attack on the continental United States by Imperial Japan and the subsequent anti-aircraft artillery barrage which took place from late February 24, to early February 25, 1942, over Los Angeles, California.[1][2][3] Five civilians died during the barrage and four Japanese aircraft were erroneously reported shot down. The incident occurred less than three months after the U.S."
- California in World War II: The Battle of Los Angeles, California State Military Museum (quoting The Army Air Forces in World War II, 1948)
- The Battle of L.A. turns 75: When a panicked city fought a Japanese invasion that never happened, Los Angeles Times (2017, reprinting its 1942 coverage)
- The Great Los Angeles Air Raid Terrified Citizens—Even Though No Bombs Were Dropped, Smithsonian Magazine (2018)
- Skeptoid #171: The Battle of Los Angeles, Brian Dunning, Skeptoid podcast (2009)