Juan asks if the Byzantines were the only ones to use Greek Fire. Greek- or ‘Roman’ Fire as it was known by those who were on the receiving end- was the closest guarded state secret of Byzantium. It’s effect was almost more devastating psychologically than physically. To watch a brother-in-arms burn alive with flames that couldn’t be put out (even under water) must have been a terrifying ordeal. Seeing pots of it come flying through the air (“like a dragon in flight” according to a French nobleman who had the misfortune to experience it first hand) shattered the morale of more than one army. Not surprisingly there were many attempts by foreign powers to get their hands on its secret. Diplomats scurried back and forth from several surrounding nations trying to deal for the recipe- but all in vain.
The emperors of Constantinople were fully aware of the value of their secret weapon. In fact, they were reluctant to use it too frequently for fear that it could be reverse-engineered or lose its psychological potency by overuse. They were right to be worried. Sometime before the eleventh century the Arabs managed to develop their own version, though it was far less effective.
It seems to have fallen out of favor with the Byzantines themselves by the 12th century- perhaps because they had lost control of the areas (around the eastern edge of the Black Sea) where they obtained the ingredients. There is a mention of its use during the 4th Crusade, but whether it was actual Greek Fire or simply ships set on fire is not clear. In any event, it’s day was done. The spread of gunpowder made Greek Fire obsolete and it disappears from history.