More than a million people have committed to storm Area 51 and “see them aliens”.

The huge action – which has prompted a threatening response from the US military – grew out of a Facebook event that has swiftly become one of the most popular ever.

Those joining the group are asked to indicate that they will help run into the base on 20 September and see what they find.

Titled “Storm Area 51, They Can’t Stop All of Us”, more than a million people have marked themselves as going and nearly a million more have indicated they are interested.

And while it is unlikely that anything at all will actually happen, it has re-focused attention on one of the most mysterious parts of the US Military.

What is Area 51?

Area 51 is a US Air Force facility – which is about everything that is officially known about what the base is doing now.

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Historically, it has been a testing ground for a variety of experimental aircraft and weaponry. In the past, reconnaissance planes such as the U-2 and F-117 have been developed and flown from there.

It is likely that it does much the same now, though anything giving any details on current operations is entirely secret.

That secretiveness has led to suggestions that Area 51 is actually focused on alien operations, either instead of or in addition to what has been more officially revealed.

Those conspiracy theories encompass a wide variety of possible uses: some say the base is storage for crashed UFOs, others suggest it might serve as a home for aliens that have made it to Earth. Others still suggest it is being used for technology that is secret though not necessarily alien, such as time travel or teleportation technology.

Where is Area 51?

The base sits in a remote part of Nevada. The nearest large city is Nevada, but it’s not very near – nothing much is, since it is located deep in the desert.

Around Area 51 are a series of alien-themed attractions. It’s one of those where the people supposedly participating in the event are told to meet, at the “Alien Center” that’s just one of the tourist attractions accessible from the nearby highway.

Why do people want to storm it?

As you’d expect from a top-secret government facility, nobody really knows what’s going on. And as you’d also expect, trying to find out is a difficult and dangerous endeavour.

If you don’t “storm” Area 51, but instead try and walk in, you won’t get very far.

The area is rigged up with a variety of motion sensors and CCTV cameras, which immediately trigger a response from very real armed guards. As numerous signs around the base make clear, those guards are allowed to use deadly force to repel people.

Flying over the base is impossible, too, since it and the area around it is completely off-limits to civilian and even military aircraft.

What has the military said about the plan?

In short, it stressed that those same deadly measures will be used against anyone trying to enter.

Air Force spokesperson Laura McAndrews said: “[Area 51] is an open training range for the US Air Force, and we would discourage anyone from trying to come into the area where we train American armed forces.

“The US Air Force always stands ready to protect America and its assets.”

Is it actually going to happen?

Most likely not. The event was created satirically, as can be seen in all of the discussion surrounding it, including the event’s description, which makes reference to a manga series.

“We will all meet up at the Area 51 Alien Center tourist attraction and coordinate our entry,” it reads. ”If we naruto run, we can move faster than their bullets. Lets see them aliens.”