The Byzantine Empire was under pretty constant assault for most of its existence, mainly from native Turkish and eventual Ottoman forces that continued to try to take out the Byzantine capital of Constantinople (present-day Istanbul, Turkey).
Considering the excellent seaside location and its relation to the Mediterranean Sea, it was a vitally important port that saw its share of navies aim at the mighty walls. Most of the time, however, Constantinople withstood the barrages. Part of it was the training of the men in battle, and the solid walls and how they were built. But a key role in the protection and defense of the city came from a weapon that wreaked a lot of havoc among the ships in the water outside the city’s walls.
This technological marvel was begun in the seventh century and was never truly duplicated, though various other cultures and empires tried to emulate it because of its crippling power. It had several names, but it was most commonly called “Greek fire.” The first known use of the weapon was late in the seventh century and was an important key in saving the city of Constantinople from a couple of massive Arab sieges prior to the rise of the Ottoman Empire.
Greek fire was a flammable liquid, which had a chemical composition that is still unknown today, and it was shot out of what were called siphons, or tubes, that were on some Byzantine naval ships as well as a shot from some of the towers along the wall of Constantinople that faced the sea. What made this weapon so dangerous to navies was that it was on fire as it traveled through the air toward the ships, but it did not extinguish once it hit the water; ships were still vulnerable if the weapon missed in the air but still could catch the wooden vessels ablaze if they got too close.
Believed to be a petroleum-based concoction, Greek fire was supposedly developed by a Jewish Syrian refugee named Callinicus of Heliopolis for Emperor Constantine IV. It was used against an Arab fleet in 673 under Constantine, another Arab siege in 717 under Leo III, and in the 10th century under Romanus I against a Russian attack fleet.
Even after some of these Byzantine weapons were captured by enemies and they investigated Greek fire and its sipons, no one could determine the exact composition of the mixture, nor could anyone fully duplicate the weaponry that fired the sticky liquid. Several tried their own combinations, including the Chinese, Mongols and Arabs.
There had been combustible and incendiary weaponry dating back hundreds of years before the Byzantine Empire, but Greek fire (also called “liquid fire” or “sea fire”) was perhaps the most effective such weapon, as some variant of it was used for hundreds of years.
The concept, in fact, has even carried forward into more modern warfare, as it could reasonably be an inspiration for the modern-day flamethrowers that are used in some war zones. But again, the actual composition of the original Greek fire was so secretive that even today we don’t really know what was in it and in what proportions. But it was perhaps the most feared weapon in naval warfare for a millennium.
Thank you to Blair Chan for providing this information.