War of the Worlds has become a legend of radio history. In 1938, "Mercury Theater on the Air" was a popular radio drama hour on the CBS network. Americans tuned in by the millions from coast to coast to hear adaptations of famous plays and literary works. On the night before Halloween 1938, the show ran a new broadcast an adaptation of H.G. Wells 1898 novel The War of the Worlds starring Orson Welles. What happened that evening would have a major effect on generations to come.
The Show
"Mercury Theater on the Air" was an unsponsored show, so it was aired without commercials. The original novel, which depicts a Martian invasion of Earth, was updated into a live newscast format. An introduction at the top of the hour explained that the adaptation was set in 1939, then a year into the future, but many listeners tuned in late and missed that introduction.
Following the introduction, the show played musical programming. Frequent news flashes broke in with reports of weather anomalies and explosions on Mars. As the show continued, the news reports became more frequent, and soon reported Martian landings across the United States. Added realism was provided via an address by the unnamed Secretary of the Interior, who happened to sound like then-President Franklin D. Roosevelt.
As the show built to a climax, the Martians were said to have begun attacking with heat rays and poison gas. The military was said to have been called in, but was unsuccessful in stopping the attacks. The Martians slowly moved en masse to New York City, leaving a trail of carnage in their wake.
In the dramatic finale, a lone reporter broadcasts from the roof of the CBS building in New York City, narrating the final moments of destruction until he, too, succumbs. A ham radio operator breaks the silence, inquiring whether there is anyone else still on air.
After the show, Orson Welles as Professor Pierson wrapped up the aftermath with a monologue, explaining that the Martians fell victim to Earthly bacteria and died. He then broke character to add a disclaimer that the show was merely fiction.
The Panic
Despite the disclaimers at the beginning and end, many Americans were not in on the hoax. The nation was consumed with the global tension that would soon lead to World War II, and was accustomed to getting news broadcasts on the radio. Many who tuned in legitimately believed that the news flashes were real.
A widespread panic erupted. Over a million people are estimated to have joined in what can only be termed mass hysteria. Police departments across the country were inundated by calls from citizens who were certain they could smell poison gas or see unexplained flashes of light. In the town of Concrete, Washington -- at the same moment that the radio program reached the segment in which the Martians invaded towns cross-country -- a transformer blew, plunging the town into darkness. Some of the worst hysteria is said to have come from that town.
The Phobia
The War of the Worlds had such a massive impact because it tapped into basic fears that are shared by many. Doomsday scenarios and alien invasions are extremely scary to many people. At a time when information was much more limited than it is today, and the nation was caught up in anxiety over the conflict that would become World War II, it is easy to see how a panic could have caught hold.
Not all fear leads to phobias, of course, and it appears that most of those who heard the radio broadcast of The War of the Worlds were able to quickly regain equilibrium. Nonetheless, the broadcast inspired fear and terror in a generation of Americans, and has become synonymous with fictional events that can lead thousands to develop phobias.
Numerous remakes and similar programs have aired since, including the 1994 TV movie that caused a similar panic, Without Warning. Discuss War of the Worlds and its spinoffs in the About.com Forum on Phobias in the Movies, and be sure to sign up for my newsletter to stay informed on the latest developments in phobias.
Source:American Psychiatric Association. (1994). Diagnostic and statistical manual of mental disorders (4th Ed.). Washington, DC: Author.

