The early morning Armed Forces Vietnam Network radio show was called Dawn Busters, and began with a greeting that boomed forth into the dawn. Each day, host Adrian Cronauer would start his show with the salutation—“Goooooood morning, Vietnam!”—with the “good” stretching out for second after second after second.

It was this call, immortalized in the 1987 Robin Williams film, Good Morning Vietnam, that got hundreds of thousands of members of the United States military out of bed, and gave them the morale they needed to take part in a war many would never have chosen. For about a year, from 1965 through 1966, Cronauer’s real-life show was broadcast out of Saigon—though it bore only some resemblance to the screenplay he eventually wrote.

Rather than being anti-war, Cronauer was a lifelong conservative who saw his role on the radio in Vietnam as a way to keep members of the military entertained as they served their country. In general, these attempts paid off: Even years later, as he told the Fayetteville Observer, “I will be at a veterans’ reunion or something, and a man will walk up to me and shake my hand and very quietly say, ‘Thank you for helping me get through ‘Nam.’ And that’s pretty rewarding.”

Though the film paints a picture of Cronauer as a radio luminary in the Vietnam War, there were multiple American Forces Radio and Television Service stations across the country, all doing similar work. Cronauer’s station, in Saigon, was the country’s headquarters. At the height of the war, these DJs broadcast to as many as 500,000 members of the military and were tasked with keeping spirits aloft. Cronauer described himself as being there “for the morale factor.” Their objective as DJs, he told Doug Bradley and Craig Werner, authors of We Gotta Get Out of This Place: The Soundtrack of the Vietnam War, was to be an antidote to homesickness. “The way to do that was to sound as much as possible like a stateside radio station. So that’s what I tried to do.”

Working for the AFVN was sometimes dangerous work—station staff at Huế, for instance, were captured and spent five years as prisoners of war—but a critical resource for scared, lonely troops, who averaged just 19 years in age, many thousands of miles from home. Most had never left the United States before being drafted. “Our mission as AFVN broadcasters was to entertain, to inform, and to soothe,” said AFVN DJ Les Howard, who was on air from from January to December 1970. “Music, especially familiar stateside songs, was a good way to do that. I believe that, in my own way, I was able to ease the stress of GIs in Vietnam.”

Along with books and cards, radio was one of the most important and popular diversions for bored troops. AFVN got good signal across much of the country, while shared transistor radios helped men to tune in wherever they were. It wasn’t necessarily the preferred choice for news, writes James Westheider in Fighting in Vietnam: The Experiences of the U.S. Soldier—broadcasts were seldom critical of the war or the American government, and were thought to give biased coverage. (The BBC was thought to be the most objective source, but was hard to reach.) But American soldiers listened for the music.

Initially, AFVN, and Cronauer, played a bland selection of “easy listening” American charts—Frank Sinatra, Tony Bennett, 1950s pop. More ribald choices, like The Beatles’ “Why Don’t We Do It In the Road,” would earn a station a slap on the wrist—some veterans bemoaned the snoozy tunes and country music favored by military stations, while many wrote home for tapes of The Doors and Jimi Hendrix. But as the war progressed, the stations grew more radical, moving into the rebellious music that dominated American airwaves back home. By the end of the war, and especially in the evening, veteran George Gersaba Jr. told Bradley and Werner, the music went completely off-track. “Late night on AFVN was reserved for progressive rock played by stoned-sounding DJs, just like the FM stations back in the world. Those low-voiced disc jockeys played everything from Roger Daltry to Procol Harum.”

Cronouar, for his part, never grew more radical in either his politics or his on-air selections. After a year on AFVN, he returned to the United States, where he trained as a lawyer. The film, he would later say, was based only somewhat on his own time serving in the war: “It was never intended to be an accurate point-by-point biography,” he said. “It was intended as a piece of entertainment. [Robin Williams] was playing a character named Adrian Cronauer, who shared a lot of my experiences.”

Cronauer died on July 18 in Troutville, Va. He was 79.