Greek Fire
Learn about Greek fire — the Byzantine Empire's terrifying secret weapon that could burn on water and helped defend Constantinople for centuries.
Greek fire was the Byzantine Empire's most feared and closely guarded military secret — an incendiary weapon that could burn on water, clung to surfaces, and was nearly impossible to extinguish. For centuries, it gave the Byzantines a decisive naval advantage that helped them defend Constantinople against sieges that would otherwise have been overwhelming.
The exact composition of Greek fire remains unknown — the secret was so closely guarded that it was eventually lost entirely. Historical sources describe a liquid that was projected through bronze tubes (siphons) mounted on ships, igniting on contact with targets. It was effective against both ships and soldiers, and its ability to burn on water made it devastating in naval engagements. The psychological impact — facing a weapon that seemed to defy nature — may have been as important as its physical destructive power.
Greek fire was first deployed during the Arab siege of Constantinople in 674–678 CE, and its use was a decisive factor in the city's survival. The technology was so sensitive that its production and deployment were controlled exclusively by the emperor. Even when Byzantium's allies requested the weapon, emperors refused — attributing the secret to divine revelation and its protection to a sacred trust. The weapon's eventual loss reflects a broader pattern in history: military secrets, unlike written knowledge, can be permanently forgotten.