The Air Force is giving land owners near Area 51 in Nevada an offer they can’t refuse: accept $5.2 million in exchange for the land, or the service will simply seize it.

Area 51 has long been the site of legends regarding government contact with extraterrestrials and other covert experiment. Similarly, the battle between property owners near the area and the Air Force has lasted just about as long. The fight has taken place for over 50 years, The Associated Press reports.

But the Air Force is now tired of waiting and has issued a deadline of Thursday for the owners to accept the offer or face seizure of 400 acres through eminent domain. Over time, the Air Force has gradually acquired the land surrounding the area, such that the 400-acre island is completely surrounded by 4,500-square-miles of government property. The only to access the island is through armed guards.

“The land has become an increasingly greater safety and security risk as demand for test and training opportunities have increased,” the government said, regarding the final offer to the owners.

The Sheahan family says that $5.2 million simply isn’t enough compensation. Not only does the family claim that the property is worth far more than the offered amount, but the Sheahans also think that adequate compensation includes damages for abuses and atrocities perpetrated against them by the Air Force and Department of Energy over decades, making the total requested compensation at about $13.6 million.

“We prefer to keep our property, but it’s for sale under the right price at the right conditions,” JosephSheahan told the AP. “Why don’t they ask themselves what it cost my family over the years in blood, sweat, tears and money?”

The harassment dates back as far as the 1950s. According to the Sheahans, that’s when a military jet destroyed their ore-processing mill. Nuclear weapons tests have further engulfed the property in dangerous radiation.

In one more recent example, the family says that guards held relatives at gunpoint when they attempted to visit the property. One of those relatives was a 7-year-old girl, who was traumatized by the incident.

The Air Force denies these incidents took place. In a statement to the Las Vegas Review-Journal, a Nellis Air Force Base spokesman said that the Air Force “is unaware of any evidence to support this claim.”

Follow Jonah Bennett on Twitter