Who- Greek fire was invented by the ancient Greeks and used by the Byzantine Empire.
What- Greek fire 'siphon projectors' were the earliest flamethrowers, which sent bursts of flaming liquid through a pressurized tube. It was usually mounted on ships and used in war at sea. The ingredients for its fuel were carefully kept secret, so no one ever found out exactly what was in it. The flamethrower was also shrunken so that it could be hand-held. However, the earliest version of Greek fire was in grenades hurled with catapults (the boat and portable versions were developed later).
When- Flaming arrows and pots were used as early as the 9th century BCE, but Greek fire was officially invented around 672 CE.
Why- It was invented to use in war. It could set wooden ships on fire and keep burning even on water.
Where- Greek fire was used in wars around the Byzantine Empire, which was located at the Mediterranean Sea.
Sources:
http://en.wikipedia.org/wiki/Greek_fire
