More than 1,100 years ago, news of an Arab raid on the Byzantine frontier could reach Constantinople in about an hour, carried not by riders but by fire. Now an independent researcher has used modern elevation data to search for the lost hilltops that may have made it possible.
The researcher, who shared the work on social media, modeled the ninth-century beacon chain that ran from the fortress of Loulon in the Taurus Mountains to the Pharos, the lighthouse of the Great Palace in Constantinople. The best route the model found used nine fires across 646 km (401 mi) and would have delivered a warning in roughly 84 minutes. The researcher stresses that the result is “a model, not the historical record.”
A fire telegraph across Anatolia
The system dates to the reign of Emperor Theophilos (829–842), a time of repeated warfare with the Abbasid Caliphate along the frontier in southeastern Anatolia. The first station, Loulon, was a contested fortress at the northern exit of the Cilician Gates, a pass through the Taurus range that changed hands several times in the ninth century.
Tenth-century Byzantine texts credit the design to Leo the Mathematician, the scholar also linked to the mechanical marvels of Theophilos’ court. The accounts appear in a treatise on imperial military expeditions attributed to Emperor Constantine VII Porphyrogenitus, in the chronicle known as Theophanes Continuatus and in the chronicle of Pseudo-Symeon.
Those sources name nine beacon stations. After Loulon came Mount Argaios, often identified with Hasan Dağı, a volcano in central Anatolia, then Mount Samos, the fortress of Aigilon, Mount Mamas, Mount Kyrizos, Mount Mokilos and Mount Saint Auxentios near Chalcedon, today’s Kadıköy, before the final fire at the Pharos. Only the first and last sites are securely identified.
The system did not spell out words. According to the texts, identical water clocks were kept at Loulon and in the capital, and the hour at which the first fire was lit told the palace what had happened. Pseudo-Symeon gives examples: a fire at the first hour meant an Arab raid, at the second hour war, and at the third hour a fire. The chain could carry up to twelve messages, one for each hour.
The idea of passing news by fire was old in the Greek world. Ancient Greeks used the phryctoriae, chains of mountaintop fire signals, and the Cycladic island of Sifnos has revived the custom with a symbolic lighting of its old beacon towers.
Searching for the lost hilltops
The new model builds on a study by historian Lucas McMahon published in Dumbarton Oaks Papers in 2025. McMahon used a GIS visibility analysis to test whether nine stations could really bridge Anatolia, a distance he puts at some 600 km. He concluded that a handful of possible routes show that the chain could in theory have worked, though some links would have had to stretch close to 100 km.
The independent researcher says they tested 372 hilltops on a 30-meter elevation model, Copernicus DEM GLO-30, and found 8,893 lines of sight long enough to clear the curve of the earth. They then ranked 1.16 billion possible chains. Assuming about ten and a half minutes for each relay, the top-ranked route of nine fires would have carried a warning to the capital in about 84 minutes.
For comparison, McMahon notes that a courier on the fast imperial post would have needed about four and a half days to ride from Tarsos, near the frontier, to Constantinople. The researcher’s figures have not been published in a peer-reviewed study and could not be independently checked.
Tolkien fans will recognize the idea from the lighting of the beacons of Gondor in The Lord of the Rings, a comparison the researcher makes too.
A short-lived system
The beacons may not have lasted long. Later chroniclers claimed that Theophilos’ son, Michael III, shut the line down because the fires distracted crowds from his chariot racing in the Hippodrome. Modern historians generally treat the story as hostile propaganda from writers loyal to the dynasty that replaced him. McMahon argues that the chain was only practical while emperor and caliph were both in the field, which helps explain why it was abandoned after the 830s.
The rivalry behind the beacons was also intellectual. McMahon ties the telegraph to competition between Theophilos and Caliph al-Ma’mun, whose Baghdad court was a center for translating Greek science into Arabic. He writes that Leo himself “had been headhunted by the Abbasid caliph.”
The independent researcher says the next step is to test the whole frontier rather than a single route. Peaks such as Hasan Dağı can see in every direction, they note, and a real warning system had to watch more than one mountain pass.
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