This may be the earliest form of naval napalm, and allowed their ships to fight with fire, with some claims that there was so much fire that it seemed like they could light the water itself.

The Byzantines usually used it in naval battles to great effect, and their opponents' ships generally couldn't escape it since the Greek fire would continue to burn, even on water. As the fire spread, more and more ships would be consumed by the fire.

By what few surviving historical accounts we have left, Greek fire could continue burning even on water and was largely responsible for many Byzantine military victories, extending the life of the empire several centuries.

During many early battles with Islamic nations over Constantinople, victory was assured only because Greek fire could not be countered, and was used to devastating effect.

What is really interesting is that accounts have the fire being transmitted in streams of fire from enemy ships, almost like a flame thrower. The exact formula for this naval medieval weapon was a secret, and actually remains a mystery to this day.

Scientists can only guess as to what it was, and how it was shot in a flame thrower form. The funny thing is, they really have no clue, showing that in some ways, our ancestors were certainly had technologies we don't have today!

There are varying accounts of where Greek fire came from, though many believe that it was invented in Constantinople by chemists who studied the early sciences. Accounts say putting water on the fire only spread it more widely, leading many historians to believe it was some form of oil.

While Greek fire gave the Byzantines a frightening weapon, they fell because they were surrounded on all sides, and eventually just ran out of population. This Greek fire was used against barbarians, Muslim invaders, and the Rus--not to mention the Venetians when the Fourth Crusade decided to sack Constantinople instead of continuing on.

Everyone knew to fear Greek fire, and it probably had the same effect that a well hidden sniper has on enemy forces in modern times.

The major down side was that Greek fire was very hard to control, and it would often accidentally set Byzantine ships ablaze, and an occasional accident could result in huge casualties in their own armies.

The effectiveness of Greek fire was obvious, but even so it had its own limitations. For example, because of its short range it was far more effective as a weapon in narrow straights or canals than in the open seas where there was room to maneuver.

From what we know, whatever the ingredients were, they were heated in a cauldron, and then pumped out of the ship in a fiery stream. Some degree of this was adapted for city use, and used in early "grenade" like form: terrifying cavalry and soldiers alike.