All of America’s elite special operations units are accustomed to operating under a veil of secrecy, but few units are more adept at secret keeping that the U.S. Army’s 1st Special Forces Operational Detachment-Delta, or Delta Force, as they’re often called. Since its very inception, Delta was intended to be a force like no other — utilizing a large officer corps and extensive and highly specialized training to produce an elite unit of war fighters that can operate at the very forefront of America’s defense apparatus. The men (and likely women) assigned to Delta are often called upon to serve as the literal instruments of America’s foreign policy, often in secret and without any form of direct support.

Perhaps it’s because of the high degree of secrecy employed by special operations units like Delta that they often come up in discussions about secret government projects, cover ups, and conspiracies. To be fair, sometimes there’s truth to be found in rumors about secret military operations on U.S. soil and beyond. The American government has a long and storied history of developing black projects that go on to serve as the backbone of its defense apparatus — from stealth aircraft to nuclear weapons — and it stands to reason that some programs are developed in cooperation with or supported by special operations troops.

Despite the long list of legends that either are true or are probably true, there are also other stories that find their way into the cultural lexicon, hanging on over the years despite their silly seeming premise. These stories often involve darker elements than scientific research or classified regime changes. Such is the case with reports of a secret base deep beneath the small town of Dulce, New Mexico — where, according to a passionate contingent of internet sleuths and UFO researchers, special operators found themselves in a firefight with aliens from another world.

Tale of the “D.U.M.B.” (Deep Underground Military Base) beneath Dulce, New Mexico may have started with a man named Philip Schneider. Schneider allegedly worked for the U.S. military in the 1970s as an engineer, helping to construct a massive network of underground installations connected by subterranean tunnels. According to the stories Schneider has told, he first became suspicious about the new tunnels they were building when he noted the presence of American special operations troops in the vicinity. Depending on the recording and source, those troops hailed from either specifically Delta Force or Army Special Forces (Schneider seems to go back and forth on this point).

It wasn’t long, according to his story, before his suspicions were confirmed — and he soon found himself standing face to face with a smelly, 7-foot tall, gray alien. He claimed that he immediately reached for his sidearm (which begs the question… why was an engineer carrying a sidearm?) and opened fire, killing the first alien and a second that appeared during the fray. A battle ensued that, per his recounting, claimed the lives of at least 60 humans and an unknown number of aliens. One special operator died loading Schneider onto an elevator and getting him to safety, but not before the engineer-turned-storyteller was hit by an alien energy weapon. As unbelievable as Schneider’s story may be, some find his evidence of this interaction rather believable — because he’s missing the fingers he claims were burned off.

What exactly is Delta Force? Here's everything you need to know

Read Next: What exactly is Delta Force? Here's everything you need to know

Schneider told his story at UFO conventions and in print, all the while claiming that the U.S. government was trying to silence him. As a result, his small contingent of fervent believers felt Schneider’s claims had been confirmed when he was found dead of an apparent suicide in January of 1996. Where some saw a tragic end to a troubled life, others saw clear signs of the very cover up Schneider had warned them about.

The story of Dulce Base extends far beyond that of Phil Schneider and a firefight between America’s best and a subterranean alien colony today. Stories about Dulce only get wilder from there, in fact, with many stories now based on the idea of a 7-layer structure housing not only human workers, but aliens of multiple races. Others have come forward claiming to have worked in the facility, offering up tales of horrible experiments being conducted on human abductees.

The truth is, the U.S. government did build a number of large underground or otherwise secret facilities during the Cold War, prompted primarily by concerns about nuclear war with the Soviet Union. Rumors about very real secret bunkers like the one built beneath The Greenbrier Resort for members of Congress swirled throughout the 1970s and 1980s.

These rumors along with an influx of movies and books about the secretive missions of Delta Force and other special operations units released during that era, created a perfect melting pot for tales about underground bases and secret alien firefights.

Of course, that’s assuming Phil Schneider was making it all up — and not everyone is convinced that he was.