Newly Uncovered Satellite Images Disprove Long-Held Theory About Roman Forts

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A collection of declassified photographs taken by American spy satellites during the Cold War has unveiled a wealth of archaeological wonders: numerous Roman forts from ancient times, previously undocumented, in present-day Iraq and Syria.

Many of those long-lost structures may be gone forever now, destroyed or damaged over the past few decades due to agricultural expansion, urban development, and war. However, the recent discovery of the forts' existence challenges a popular hypothesis established in the 1930s regarding the role of such fortifications along the eastern border of the ancient Roman Empire, as reported by researchers in the journal Antiquity on Wednesday.

This photograph shows ripples in the surface of Denman Glacier in East Antarctica that throw shadows against the ice. The glacier is melting at a faster rate now than it was from 2003 to 2008.

NASA

Scientists have uncovered an ancient landscape in a region on Earth that is less familiar to us than the surface of Mars. Analysis of satellite imagery has revealed a significant number of fortifications that are widely distributed, challenging the long-held belief that these structures were constructed solely for defensive purposes. Instead, it is now believed that these forts were built to facilitate the secure movement of caravans and travelers along frequently traversed routes that were frequented by nonmilitary traffic. The study authors propose that these forts served as outposts and safe havens, rather than imposing barriers.

Lead study author Jesse Casana, an archaeologist and professor in the department of anthropology at Dartmouth College in New Hampshire, stated that the high-resolution images analyzed in the recent study were captured during flyovers by multiple satellites from two US military programs: the Corona Project (1960 to 1972) and Hexagon (1971 to 1986). The Corona images were declassified in 1995, while the Hexagon photos were made available to the public in 2011. These images from Hexagon and Corona are of immense value to archaeologists as they provide visual records of landscapes that have undergone significant changes over time.

"Agriculture and urbanization have significantly devastated numerous archaeological sites and features," said Casana during an interview with CNN. "These historic images provide us with the opportunity to observe objects and structures that are frequently hidden or no longer present in the modern era."

Comparison: Spy satellite photos versus the Poidebard survey.

Satellite imagery is invaluable for exploring the northern region of the Fertile Crescent in the Middle East, stretching from the eastern coast of the Mediterranean to western Iran. This is due to the significance of the area in archaeology and the clear visibility of the ground captured in the photos, as highlighted by Casana.

The research team meticulously examined the images in search of indications of Roman forts, identifiable by their distinct square shape and walls typically measuring around 164 to 262 feet (50 to 80 meters) in length. They initiated their investigation by referring to maps derived from an aerial survey of the region conducted by French archaeologist and Jesuit missionary Father Antoine Poidebard during the 1920s and 1930s. This groundbreaking survey, which involved capturing aerial photographs of archaeological sites, led Poidebard to report the discovery of 116 Roman forts in 1934.

Here are a few aerial photographs taken by Jesuit missionary and archaeologist Father Antoine Poidebard in 1934. The images include the following (clockwise from top left): the fort at Qreiye, a Roman fort and medieval caravanserai at Birke, the fort at Tell Zenbil, and the castellum at Tell Brak.

Father Antoine Poidebard's accomplishment was truly remarkable. However, almost a hundred years later, the task of mapping his forts using satellite photos proved to be quite challenging. This was mainly due to the fact that Poidebard's map lacked a large-scale perspective, resulting in various spatial inaccuracies. Additionally, Poidebard's identification method for the forts was quite vague, as he relied on their proximity to geological landmarks rather than assigning specific names or numbers to them.

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According to Poidebard, these forts were strategically positioned in a north to south alignment, serving as a defense line against eastern invaders during the Roman Empire. However, the recent research discovered that Poidebard's survey only provided a limited perspective on the ancient infrastructure of Rome. The satellite photos unveiled a remarkable revelation – the line of 116 forts actually represented just a small portion of a larger cluster of 396 fortified structures, extending from east to west.

According to the study, the forts covered a vast area of approximately 116,000 square miles (300,000 square kilometers). They extended from Mosul, located on the Tigris River in Iraq, all the way across Ninawa province and the Khabur and Balikh valleys. The forts further stretched towards the semi-arid plains to the west of the Euphrates River, ultimately reaching western Syria and the Mediterranean. These forts provided oases of safety for ancient Rome.

During a subsequent survey, archaeologists discovered a total of 106 additional fort-like structures within a specific section of the image. This discovery strongly indicates that further investigations will unveil a significant number of additional Roman forts. Based on excavations conducted at other Roman sites in the same area, experts estimated that these forts were constructed between the second and sixth centuries.

Contrary to the belief that Poidebards' string of forts on the eastern frontier of the Roman Empire served solely as military fortifications, this new evidence suggests that these fortifications collectively served a different purpose. Instead of serving as an impenetrable barrier in a volatile border region, they functioned as safe havens that provided order and security along the extensively-traveled Roman roads.

According to Casana, borders were not barriers but rather places of cultural exchange and the movement of goods and ideas. He believes that this perspective can teach us a lesson in the modern era. As an archaeologist, Casana claims that throughout history, there have been numerous unsuccessful attempts by ancient states to construct walls along borders. He emphasizes that if archaeology has any contribution to offer in contemporary discussions, it should be the understanding that building massive walls to prevent people from entering is a flawed strategy.

Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American and How It Works magazine.