A brutal, ritualized method of torture and execution that was allegedly practiced by Nordic people during the Viking Age was so gruesome that some scholars questioned whether it was even possible to perform on a human body.

However, researchers recently found that the act known as blóðǫrn, or "blood eagle," was in fact anatomically possible and could have been performed with known Viking weapons.

According to descriptions of the blood eagle in poems and prose dating from the 11th century to the 13th century, victims were typically captured in battle. Captors would cut and open large flaps of skin and muscle from their living victim's back and then sever the ribs from the spine, opening the ribs out to the sides to form "wings." The torturer would then complete the ritual by pulling out the victim's intact lungs and laying them over the extended ribs (by this point, the victim was certainly deceased, the researchers wrote). Performing such a horrific act would have been "anatomically challenging" for the torturer — but it would not have been impossible, scientists reported in the January 2022 issue of Speculum: A Journal of Medieval Studies.

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In the new study, the researchers evaluated the blood eagle practice by first analyzing human anatomy, breaking down the sequence of the torture step by step and approximating how it might have been accomplished in a public ritual. They then looked at weapons from that era, to see how diverse blades might have been used for a task so laborious and grisly.

Certain types of Viking knives, swords and spears may have been wielded for different parts of the blood eagle ritual, and prior archaeological discoveries include examples of weapons that would have been well-suited for this gruesome practice. Single-edged "fighting knives" with rigid handles have been found in elite Viking burials, and some resemble large knives that are used in modern autopsies, according to the study. Such a knife could have been used to cut and peel back the skin and muscle layers for the first part of the blood eagle ritual.

Severing the ribs was a trickier task — particularly if the lungs needed to remain undamaged, as hacking at them with a sword or sawing with a serrated knife would have likely torn or punctured the lung tissue. However, ribs could potentially be "unzipped" from the spine with a small, barbed spearhead, and such weapons have also been recovered from Viking burials, the researchers reported.

Archaeologists have never found human remains that display signs of having endured this ritual. But in the nine known written accounts of the blood eagle ritual, the people who ordered the torture and their victims were men of elevated social status, and most of them were royal, according to the study. In some cases, the texts suggested that a designated official was on hand to perform the blood eagle act, perhaps because it required highly specialized knowledge of anatomy and butchering.

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Performative displays of social standing and ritualized executions that included "conspicuous mutilation" were common practices in elite circles of Viking society; this suggests that written accounts of the blood eagle ritual were describing events that actually happened and were socially significant for leaders celebrating victory over a powerful enemy, the researchers said.

"The blood eagle was thus no mere torture: it had meaning," the researchers wrote in the study.

While dissecting a living human body in this way was within the realm of possibility, surviving such torture was not. Victims likely lost consciousness early in the process as flesh was removed from their backs; the quantity of blood loss and subsequent lung collapse would have killed them long before the grisly ordeal was finished, and "much of the procedure would have been performed on a corpse," the scientists reported.

"There is no possibility that a victim would have remained alive throughout the procedure," the researchers wrote. "It is clear that a victim undergoing a 'full' blood eagle would have died long before their ribs could have been formed into the shape of wings and their lungs externalized."

Originally published on Live Science.