On June 3, 1944, at 4:39 p.m. Eastern War Time, just as the thoroughbreds thundered into the final turn of the Belmont Stakes, CBS interrupted sportscaster Ted Husing’s breathless call. A news flash: The Associated Press was reporting that the highly anticipated invasion of France had begun. Noting the scanty and unconfirmed information, the CBS announcer told the audience to stay tuned, and the network returned to the horse race.

Less than three minutes later the Associated Press killed the erroneous story. CBS again broke into the sportscast and retracted the report.

It was too late. NBC and the Mutual Broadcasting System followed CBS, reporting that D-Day had begun. In an instant, the “news” swept the nation. Shocked radio listeners telephoned friends. “The potency of the words stirred millions into electric activity,” reported the Brooklyn Daily Eagle. In New York City, Major League Baseball’s Giants and Pirates paused their game when the invasion was announced. “There were only 9,000 people at the Polo Grounds,” remembered one spectator, “but the roar that went up could have been from 90,000. We all leaped to our feet, yelled, pounded the backs of total strangers, and had mental images of the war’s ending soon. When the yelling subsided, the announcer said: ‘We ask that you all rise for a minute of silent prayer.’ ”

The New York Times reported that millions of people had heard the report on as many as 500 stations nationwide. It would later be revealed that a pre-planned news flash had escaped when Joan Ellis, a young typist in the AP’s London bureau, accidently pressed the wrong button on her teletype transmitter. At 6:30 p.m. on June 3, less than two hours after the initial report, NBC’s Harold Fleming described the sequence of events on a radio program called The People’s War:

Once again, good evening, and first as usual, folks, I want to bring you the late war bulletins from the NBC studios here in New York. Less than two hours ago, the Associated Press flashed word that allied troops had landed in France. But, almost immediately, AP followed with the announcement “kill flash, false report.” It seems that an inexperienced London operator was the cause of the erroneous report. The AP explains that the flash was sent in error by a new operator who was practicing without authorization.

Though far more Americans heard the false D-Day report than tuned in to Orson Welles’ War of the Worlds broadcast, the erroneous news flash, and the public’s reaction to it, is now largely forgotten. Actual coverage of D-Day, starting three days later, wiped it from historical memory. This June marks the 70th anniversary of D-Day, a remarkably historic broadcasting event, and the networks will no doubt commemorate their invasion coverage. Audio from the battle, recorded live using sophisticated new technologies, has been preserved and digitized. New generations of listeners can thrill to the voices of George Hicks, John MacVane, and Charles Collingwood, whose battlefield reports crackled across the ocean seven decades ago.

But we also should take a moment to remember the day that Allied Forces did not invade France. There’s some fascinating history here, and an important lesson about journalism that’s still relevant today.

In the 1940s, American broadcast journalism was hindered by a strange quirk: the network rule that all broadcasting on the national airwaves had to be live. Recorded programs had been strictly forbidden on stations affiliated with NBC and CBS since the late 1920s, when so-called transcription services threatened to kill commercial network radio in its infancy. The radio industry originally cut a deal with AT&T to exclusively rent telephone lines (and air live programming) in order to keep the telephone company out of commercial broadcasting. But when advertisers balked at the high toll charges, record companies sprang up to cut out the middlemen. In 1930, for example, Chevrolet built its own network to air the Chevrolet Chronicles, contracting with 170 stations and mailing them recordings. As historian Alex Russo notes, furious NBC and CBS executives countered by tightening their ban on the airing of recorded material by network affiliates.

Before World War II, the ban on prerecorded material was broken only in exceptional circumstances, such as the 1937 Hindenburg disaster. When war broke out, the ban frustrated American newscasters. “Time after time, [Fred] Bate, [Edward R.] Murrow, [Larry] LeSueur, and I went up to the BBC roof with our microphones,” remembered NBC’s John MacVane. “A few moments before the circuit opened to New York, it might sound as though the doors of hell were being blown off their hinges, but invariably, as soon as New York said, ‘Go ahead, London,’ a lull ensued for as long as we were broadcasting. … Nothing would be picked up.”

Meanwhile, battlefield recordings riveted English, Russian, and even German citizens. Perhaps the greatest battlefield team of all was the small group from the Canadian Broadcasting Corp. In 1943, CBC engineers constructed a small mobile recording studio in a van to capture the sounds of war. Recordings made during the invasion of Italy caused a sensation when picked up by American citizens living near the Canadian border. “The poor, government-financed CBC had bested the wealthy U.S. networks,” explained the CBC’s Peter Stursberg, calling it a “remarkable feat in itself, but not a very difficult one since the Americans had a rule. … There could be no recordings of news programs.” The rule, CBS’s William L. Shirer recalled, was “ridiculous.”

Because the CBC and BBC had canned recordings ready to go for D-Day, and because no competition existed on their airwaves, these governmental broadcasters were protected from the pressures facing their American counterparts. CBS, NBC, and Mutual executives, by contrast, hoped to scoop each other as the invasion neared. The war had already transformed news into the most profitable broadcasting genre, and being first to air with the invasion bulletin would be an unprecedented coup. No wonder CBS jumped when Ellis’ teletype transmitter buzzed into action.

The real D-Day did more to end the ban on recordings than any other news event. The only plausible way to cover the invasion was by capturing audio, so embedded reporters were outfitted with innovative recording devices. Once Americans heard sound from Normandy, the networks rarely handicapped breaking news coverage for purely anticompetitive reasons.

Today, the radio era can seem as distant as Gettysburg. Seventy years is a long time, but in March of this year Richard C. Hottelet, who covered D-Day for CBS News, spoke to a class at the University of Maryland. And the CBC recently celebrated the achievements of Peter Stursberg, their outstanding war correspondent, on the occasion of his 100th birthday.