İkinci Dünya Savaşı sırasında, Büyük Britanya, iddialı bir Skotya adasında koyunları antrakla zehirledi.

Any tourists driving the remote coasts of Wester Ross in the northwest Scottish Highlands would be forgiven for overlooking Gruinard Island. After all, this low, featureless hump has nothing on the dramatic sweep of the Summer Isles, with impressive peaks like Beinn Ghobhlach (“the forked mountain” in Scottish Gaelic) grabbing all the attention.

But this unassuming island holds decades of secrets in its soil. It has been the site of secret bioweapon tests, bioactivist plots, and a 50-yearquarantinethat sealed the island off for nearly half a century. This is the story of Anthrax Island.

In 1942, British Prime Minister Winston Churchilldispatched a team of military scientistsfrom the Porton Downmilitaryresearch facility to the northwest Highlands. He was afraid that the Nazis were planning to unleash a biological bomb. Eager not to be outdone, Churchill asked the scientists to test whether they could create a bioweapon for Britain using the bacteriumBacillus anthracis.

B. anthracisis a soil-dwelling bacterium that, for being only a few micrometers long, causes a lot of trouble. When the bacteriumsenses starvation, it forms specialized cells called spores, which can withstand radiation, heat, cold, and chemical disinfectants. These spores are also packed with toxins that causeanthraxin humans and other animal species.

Thisdiseaseis no joke. In animals like cattle, there’s little outward sign of illness until the infected suddenly drop dead, saysGeorge C. Stewart, a retired microbiologist at the University of Missouri.

“At that point, they’re hemorrhaging out of all of their orifices, out of the mouth, the anus, any sort of lesions in the skin,” says Stewart. The thick, blackish blood that leaks out of these dying animals pours into the ground, infecting it withspores.

Humans are usually infected through contact with animals.Sporescan enter through a cut in the skin or be inhaled or ingested. Each type of infection causes different symptoms, but can include black, swollen blisters, chest pain, fever, and chills.

Any infection can progress to a systemicdiseasethat poisons the blood and body. Cutaneous anthrax, which enters the body through cuts or other breaks in the skin, is the least deadly form of the disease. But it still kills one in five people who become sick with it. However, a pre-exposure vaccine can provide protection.

The British Ministry of Defense identified Gruinard Island as a viable site for testing the bacterium’s impact. It was uninhabited and separated from the mainland, but still accessible through a short boat trip. The scientists told locals nothing about what they were doing.

The details only really emerged 50 years later, when the Ministry of Defense released a video showing some of the experiments they had been conducting. In the grainy footage, containers filled withB. anthracisare placed facing a herd ofsheepbrowsing on Gruinard’s low grasses, unaware of the danger.

The government had bought or borrowed sheep from the mainland, and shipped them over to the island. Needless to say, the sheep all died. Their corpses were burned or buried. The tests had worked, but arguably too well.

“Back in the early days of the war, there weren’t many studies, if any, talking about persistence of spores in [the] soil.” says Stewart. On Gruinard, thehardy sporeshunkered down, waiting for a new host to infect-even decades later.

After killing thesheep, the government compensated locals for their dead animals, lying about how the sheep had died. They told locals the sheep had perished after they were exposed to a toxin released from a nearby Greekshipwreck.

The British government then sealed the island off for the next 40 years. Incredibly, warning signs telling locals not to visit the island didn’t even mention the presence of a deadly bioweapon until the late 1960s.

Other scientists from the Porton Down military research complex revisited the island over the decades, finding that efforts to burn the bacteria had failed. In the mid-1980s, an activist group called the Dark Harvest Commandos decided they had had enough of the government’s indifference. They decided to put a spotlight on the contaminated island.

Dark Harvest sailed to Gruinard and dug up soil samples. Even decades later, anthrax spores can survive in these conditions, saysMonika Ehling-Schulz, a microbiologist at the University of Veterinary Medicine Vienna.

“The spores allow the organisms to sleep for many, many years,” she says. Her team has dug up living anthrax samples that may have been dormant for 80 years inprevious research.

The activists sent a letter toThe Glasgow Heraldnewspaper. “By the time you read this, the campaign will have started in earnest. The first delivery will have been made-and where better to send the seeds of death than to the place from whence they came?”

The activist Commandos struck first at Porton Down. Outside the facility, researchers found a bucket of anthrax-infected soil. A few days later, another soil sample was left at the Blackpool Tower, where the ruling Conservative Party’s conference was being held.

Investigators who tried to unmask Dark Harvest scoured the local Highland communities, but got nowhere in their inquiries.

Then, the guerilla activists left a final letter pinned to the door of a government office later that year, stating that their aims had been met. Gruinard’s contamination was now headline news, and just a few years later, thegovernmentsent a major taskforce to the Highlands to tackle the islands’ unwelcome visitors once and for all.

Stewart explains that the scientists carted off the island’s entire topsoil layer. “Then they mixed formaldehyde with seawater and flooded the island several times.”

This approach isn’t a specialized technique for anthrax spores, says Ehling-Schulz. “Formaldehyde is going to kill everything,” she adds.

The strategy worked. By 1990, the government had declared Gruinard anthrax-free and removed the final warning signs prohibiting visits.

Now, visitors can travel to the island freely, and the bay surrounding it is a popular spot for kayakers who cut through the unusually blue waters. Even considering the persistence and peril of anthrax, Stewart reckons that the British government did properly decontaminate the island. It’s just a shame it took them nearly 50 years.

InThat Time When, Popular Science tells the weirdest, surprising, and little-known stories that shaped science, engineering, and innovation.

Update, August 7, 2026, 11:50 a.m. ET:This story incorrectly said England poisoned sheep with anthrax. The wider British government poisoned the sheep.