Greek Fire – The Top Secret Weapon of the Byzantine Empire


During the Middle Ages, the fortified city of Constantinople, the imperial capital of the Byzantine Empire, was considered unconquerable. It was not the city’s large thick walls that guaranteed safety for its inhabitants, however. It was something far more terrifying than the walls and the men that defended them.

The Byzantine Empire had developed an incendiary weapon in c. 672, dubbed The Greek Fire by the Western Crusaders, that repelled enemies superior in numbers throughout the centuries. The Byzantines used a variety of names for the weapon such as sea fire, Roman fire, liquid fire, war fire and sticky fire ― all implying the characteristics of the mixture used to set ships a flame during naval battles.

Topographical map of Constantinople during the Byzantine period. By Cplakidas - Own work, CC BY-SA 3.0.
Topographical map of Constantinople during the Byzantine period. By Cplakidas – Own work, CC BY-SA 3.0.

Since the city of Constantinople (today’s Istanbul, Turkey) was located on the banks of a natural strait, Bosphorus, on the coast of the Marmara Sea, the invaders often used a naval force in their attempts to besiege the fortress of Constantinople. The city, in order to defend itself, as the heart of the Byzantine Empire, was in need of a superior weapon, that would disintegrate the enemy fleet, sparing the Greek fleet as much as it was possible.

The invention of the weapon is ascribed to a certain architect from Heliopolis (today’s Baalbek, Lebanon) called Calinicus. This attribution is based on the claims of a Greek chronicler, Theophanes, whose description of the weapon and its effects remains the oldest living testimony. Due to several chronological contradictions, historians had dismissed the theory that the Greek fire was a product of a one man’s design, but rather claim that it was produced in the Constantinople’s chemical laboratories by a team of experts, as a state-funded weapon project.

Therefore, the weapon’s formula was a state secret and the original ingredients of the mixture remain unknown to this day. Modern scientists  continue to debate about the formula, with various proposals including combinations of pine resin, naphtha, quicklime, calcium phosphide, sulfur, or niter.

The weapon’s main trait was that it produced a fire that could burn on the surface of the water. This made it a perfect weapon for sea battles between wooden ships. The iconic image of the fire on water would cause fear among the enemies of the Empire, especially because the weapon couldn’t be reproduced by anyone else except the Byzantines.

These masters of the Mediterranean Sea introduced the offensive capacities of the Greek Fire, by implementing specially designed ships that were equipped with devices resembling flamethrowers. This new weapon appeared when it was needed the most ― weakened by its long wars with Sassanid Persia, the Byzantines had been unable to effectively resist the onslaught of the Arab conquests. Within a generation, Syria, Palestine, and Egypt had fallen to the Arabs, who in c. 672 set out to conquer the imperial capital of Constantinople.

Greek fire was used to great effect against the enemy fleets, helping to repel the conquerors at the first and second Arab sieges of the city. The weapon continued to be in active use, with reports of victories gained by the advantage of the feared fire dating all the way to the 13th century. It was a vital instrument in crushing both foreign incursions by Arab and Slavic invaders and local rebellions. During the Byzantine expansion in the late 10th and early 11th century, the battle proved to be vital in a number of naval battles against the Saracens.

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