In February 1942, the United States was still adjusting to World War II. Pearl Harbor was only two months past, and Americans entertained fears of an imminent Axis attack on the mainland. Such fears weren’t entirely unjustified: German U-Boats in the Atlantic began a sustained campaign of terror against Allied merchant vessels, often within sight of American and Canadian coastal towns. A few months later, the FBI arrested a team of Nazi saboteurs on Long Island; they proved to be more bumbling amateurs than a serious threat, but their exorbitant plans to destroy American military and transportation infrastructure seemed to justify fears of internal subversion.

On the opposite coast, it proved even easier for traditional racism against Japanese-Americans to take hold. While Japanese submarines weren’t as pervasive as their German counterparts, they did sink a good many American ships in the Pacific in the first months of the war. And occasionally they ranged further; on February 23, 1942 the I-17 bombarded a fuel depot at Ellwood, California, just west of Santa Barbara. That Japan, even at the height of its conquests, lacked the resources to transport an invasion force across the Pacific did not occur to Californians, who began to eye their Asian neighbors with suspicion and hatred. After Pearl Harbor, anything seemed possible.

The next evening, February 24, authorities issued a military alert for Los Angeles, indicating a possible attack was imminent. It’s unclear what triggered this alert: over the past few weeks, Naval and Coast Guard ships had reported “Japanese vessels” outside the cities which often turned out to be debris or animals misidentified by panicked sailors. Most likely, the Ellwood incident merely inflamed extant fears and paranoia, stoked unsubtly by both state and national authorities. Troops were called out, searchlights readied, antiaircraft batteries manned, and the City of Angels settled into an uneasy vigil.

Around 2:00 am on February 25, a radar station picked up an unidentified bogey 120 miles south of the city. After ordering a blackout on the city, antiaircraft troops in Santa Monica received authorization to fire at will on any objects spotted overhead. The Army Air Force remained skeptical, deciding to ground its aircraft until they received confirmation of an attack. But as time passed, reports began to filter in claiming that enemy aircraft were approaching the city. One spotter on Long Beach claimed to see “25 planes” passing overhead; another report claimed to spot a balloon with a red flare drifting ominously towards the city.

Soon after 3:00 am, after the “balloon” was sighted over Santa Monica, the city’s defenses “erupted like a volcano.” Shells smashed into buildings; civilians in the streets ducked for cover or hunkered in basements. Several car accidents occurred, and a few witnesses suffered heart attacks amidst the chaos. The sky was lit up with blaring searchlights and exploding shells, providing a spectacle for souls brave enough to watch through their windows, and a thick haze of smoke soon settled over the city. At least 1,400 rounds were fired in an hour, before the firing ceased.

Initial reports were “hopelessly at variance,” a later Army report claimed. The initial sightings of planes and balloons were compounded by the media coverage, which fanned flames of speculation; a heavily retouched photograph of the searchlights evidently aiming at an object splashed across newspapers nationwide. The Los Angeles Times ran a feature claiming that 50 enemy aircraft had been spotted over the city. Another woman saw neat formations of aircraft, improbably lit in the dead of night, over the city. A few reports claimed to have seen bombs falling (most likely anti-aircraft shells), that two aircraft had been shot down, even that Japanese paratroopers had landed in the city, though none could be found. As for the balloon, it might well have been a zeppelin out of which Japanese bombers flew.

The government did nothing to dispel these rumors. Although Secretary of the Navy Frank Knox declared the incident a “false alarm,” Secretary of War Henry Stimson pronounced the “Battle of Los Angeles” an attack by Japanese planes based in Mexico, or based on a submarine aircraft carrier – ludicrous claims that, in the moment of panic, seemed plausible enough. This wasn’t enough for Congressman Leland Ford, who blamed the attack on the Roosevelt Administration wanting to “lay a political foundation to take away Southern California’s war industries.”

The Battle of Los Angeles caused significant material damage, and the deaths of at least five civilians. But its real victims were Japanese-Americans. President Franklin Roosevelt had already signed Executive Order 9066, authorizing the internment of Japanese-Americans in camps, on February 9th. The LA panic, along with the Ellwood raid, were cited as justification to carry out these policies posthaste. Within a matter of weeks, the wholesale evacuation of Japanese-Americans from California and other Western states was under way, ensuring that the farce had a tragic ending.

A military study in 1983 determined that the Battle resulted from wartime mass hysteria. The “balloon with a red flare” was determined to have drifted from a meteorological station further down the coast. There was no evidence of self-propelled aircraft, enemy or otherwise, over Los Angeles that night; “cold detachment disclosed no planes of any type in the sky,” one soldier wrote. This didn’t stop conspiracy theories, including latter-day claims that UFOs paid the war-scared city a visit. Nor did it stop Steven Spielberg from making 1941, which was in part inspired by this incident.