In 1947, a high-altitude balloon crash-landed in Roswell. The aliens never left.

In Roswell, New Mexico, exactly seven decades ago this month, the first little green men arrived.

But we’re getting ahead of ourselves.

Let’s start closer to the beginning. On June 14, 1947, a rancher named W.W. “Mac” Brazel and his son Vernon were driving across their ranchland some 80 miles northwest of Roswell when they encountered something they’d never seen before. It was, in Brazel’s words, “a large area of bright wreckage made up of rubber strips, tinfoil, and rather tough paper, and sticks.”

The metallic-looking, lightweight fabric was scattered, shredded across the gravel and sagebrush of the New Mexico desert. Brazel didn’t know what to do with the newfound items, or how they had landed on the property, so on July 4 he collected all of the mysterious wreckage he could find. On July 7, he drove it all to Roswell, delivering the goods to Sheriff George Wilcox.

Wilcox, too, was confounded.

Seeking answers, he contacted Colonel “Butch” Blanchard, commander of the Roswell Army Airfield’s 509th Composite Group, located just outside of town. Blanchard was stymied. Working his way up the chain of command, he decided to contact his superior, General Roger W. Ramey, commander of the 8th Air Force in Fort Worth, Texas.

Blanchard also sent Major Jesse Marcel, an intelligence officer from the base, to investigate more thoroughly. Accompanied by the sheriff and Brazel, Marcel returned to the site and collected all of the “wreckage.” As they tried to ascertain what the materials were, Marcel chose to make a public statement. On July 8, Marcel’s comments ran in the local afternoon newspaper, the Roswell Daily Record, alongside a headline stating “RAAF Captures Flying Saucer on Ranch in Roswell.”

The body of the story contained a dramatic, memorable sentence: “The intelligence office of the 509th Bombardment Group at Roswell Army Air Field announced at noon today, that the field has come into the possession of a Flying Saucer.”

“Apparently, it was better from the Air Force’s perspective that there was a crashed ‘alien’ spacecraft out there than to tell the truth,” says Roger Launius, the recently-retired curator of space history at the Smithsonian’s National Air and Space Museum in Washington, D.C.

“A flying saucer was easier to admit than Project Mogul,” Launius adds, a chuckle in his voice. “And with that, we were off to the races.”

It was after the close of World War II, a time when nuclear weapons cast a long shadow. Truth-telling was not a priority, and there were remarkably unusual events underscoring the situation at hand.

Everywhere you looked in 1947, the global, social and political chessboard was being re-divided. The Soviet Union began to claim eastern European nations for itself in a new post-war vacuum. Voice of America started broadcasting in Russian to the eastern bloc, peddling the principles of American democracy. The U.S. sent V2 rockets carrying payloads of corn seeds and fruit flies into outer space. The Bulletin of Atomic Scientists set the “Doomsday Clock” ticking, and the Marshall Plan was in the making to rebuild war-torn Europe. Small wonder that in the heat of summer that year, flying saucers became all the rage.

On June 21, Navy Seaman Harold Dahl claimed to have seen six unidentified flying objects in the sky near Maury Island in Washington state’s Puget Sound. The next morning, Dahl said he was sought out and debriefed by “men in black.”

Three days after the Dahl sighting, an amateur pilot named Kenneth Arnold said he had spotted a flying saucer in the sky by Mount Rainer, Washington.

“UFOs aren’t unusual,” Launius says. “They’re simply unidentified things you see in the sky. We’ve all probably seen them. And, if you look long enough, you’ll probably eventually figure out what it is you’re looking at. It’s not extraterrestrials.”

By the end of 1947, mass hysteria had seized the global mindset, with more than 300 alleged “flying saucer” sightings in the last six months of that year alone.

“Not that there was ever any credible evidence to support the sightings,” Launius adds.

By early July 1947, Brazel had heard tales of flying saucers in the Pacific Northwest. These sightings spurred him to show his discovery to the authorities, but just one day after the Air Force announced it had come into possession of a flying saucer, Roswell’s morning newspaper debunked the story.

A published statement from the War Department in Washington claimed the debris collected on Brazel’s ranch was the remains of a weather balloon, and the Roswell Dispatch’s morning headline, “Army Debunks Roswell Flying Disc as World Simmers with Excitement,” set the tale to rest on July 9.

“But we need to back it up, here,” says Launius. “What was really going on was something called Project Mogul.”