Greek fire: a brief history.

 Greek fire was an incendiary weapon used by the Roman Empire beginning c. 666. Used to set fire to enemy ships, it consisted of a combustible compound emitted by a flame-throwing weapon. Some historians believe it could be ignited on contact with water, and was probably based on naphtha and quicklime. The Byzantines typically used it in naval battles to great effect, as it could supposedly continue burning while floating on water. The technological advantage it provided was responsible for many key Byzantine military victories, most notably the salvation of Constantinople from the first and second Arab sieges, thus securing the Empire's survival.

The impression made by Greek fire on the western European Crusaders was such that the name was applied to any sort of incendiary weapon, including those used by Arabs, the Chinese, and the Mongols. However, these mixtures used formulas different from that of Byzantine Greek fire, which was a closely guarded state secret. Byzantines also used pressurized nozzles to project the liquid onto the enemy, in a manner resembling a modern flamethrower.

Although usage of the term "Greek fire" has been general in English and most other languages since the Crusades, original Byzantine sources called the substance a variety of names, such as "sea fire" (Medieval Greek: πῦρ θαλάσσιον pŷr thalássion), "Roman fire" (πῦρ ῥωμαϊκόν pŷr rhōmaïkón), "war fire" (πολεμικὸν πῦρ polemikòn pŷr), "liquid fire" (ὑγρὸν πῦρ hygròn pŷr), "sticky fire" (πῦρ κολλητικόν pŷr kollētikón), or "manufactured fire" (πῦρ σκευαστόν pŷr skeuastón).

The composition of Greek fire remains a matter of speculation and debate, with various proposals including combinations of pine resin, naphtha, quicklime, calcium phosphide, sulfur, or niter. In his history of Rome, Titus Livy describes priestesses of Bacchus dipping fire into the water, which did not extinguish, "for it was sulphur mixed with lime."