What is "Greek fire"?

Greek fire was used by the Byzantine Empire as an incendiary weapon against warships, since it could continue to burn while the burning material floated on water. It was first developed around 672 AD and gave the Byzantine Empire an advantage over their enemies, notably against Arab invaders. Use of Greek fire has been attributed in part for saving the Empire from conquest between the 7th and 12th centuries.

The Byzantines kept the formula for their Greek fire a state secret, so the exact composition of the material is a matter of conjecture and debate. Various combinations of pine resin, naphtha, quicklime, sulfur and other materials have been suggested as possible formulations. Other incendiary weapons of the time, such as those used by the Chinese, Arabs and the Mongols were of different composition, plus the Byzantines used pressurized nozzles to project the weapon onto their targets.

The incendiary weapon was commonly referred to as "Greek fire" in English and other languages since the Crusades. Byzantine sources used a variety of names, such as "sea fire", "liquid fire", "sticky fire" and "manufactured fire".