Between 1941 and 1943, an exceedingly peculiar series of transmissions reached radio sets in Germany. The broadcaster called himself Der Chef, or the chief, and his Berliner accent and prodigious knowledge of military affairs suggested he was a high-ranking German of the old guard, probably an army officer.

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A patriot and Hitler loyalist, Der Chef bemoaned the corruption enveloping Nazi headquarters while the war was being fought across Europe. He disclosed worrying news that injured German soldiers were receiving infusions of syphilis-tainted blood from captured Poles and Slavs, and gossiped about an Italian diplomat in Berlin who was bedding the wives of German officers. German civilians picking up the shortwave radio transmissions thought they were eavesdropping on the affairs of a secret military organ led by Der Chef.

“Had his listeners been able to take a peep at the surroundings in which his messages were, in fact, recorded,” the British journalist Sefton Delmer wrote years later, “our audience would, I am sure, have shrunk to zero.” Delmer knew of what he spoke: He had helped create Der Chef.

Although this was hardly the first instance of a wartime disinformation campaign, Delmer’s “Black Propaganda,” as he called it, shared plenty with today’s “fake news.” It was agitprop masquerading as inside dirt. To be sure, British intelligence agents played a role, but it was behind the scenes, unlike traditional government propaganda. By most accounts the broadcasts were insidiously effective: Hitler’s high command repeatedly attempted to block the signal.

It turns out that Delmer, the subject of a new documentary, Come Before Winter, developed a fake news factory aimed at disrupting the Nazis. He introduced several other radio stations, including one anchored by a young German named “Vicki,” who read a mixture of real news culled from intelligence sources and fake items, including a fabricated report about an outbreak of diphtheria among German children.

In November 1943, Delmer ended Der Chef’s reign of error by penning a script that had Nazi troops storming the studio and “shooting” him mid-broadcast, but many other ruses lived on. Beginning in May 1944, he produced a German-language newspaper called Nachrichten für die Truppe (News for the Troops), which was air-dropped to soldiers on the Western front.

After the war, Delmer rejoined Britain’s Daily Express, revealing his earlier role as a source of fake news in a 1962 memoir. “Delmer was proud of his work,” says Gary Blount, producer of Come Before Winter. “His broadcasts had not only been heard extensively, but had contributed to the war effort.”