A secret weapon with an unclear recipe
Greek fire was an incendiary weapon used by the Byzantine Empire, notably at sea, from the later seventh century. It is described in Byzantine and foreign sources as a liquid that burned fiercely, was difficult to extinguish with water, and could be projected from a tube mounted on a ship. Beyond that, much remains uncertain. No reliable account of the exact composition survives, and the formula was treated as a state secret.
Many modern writers suggest the mixture was based on petroleum or a similar flammable substance, perhaps with resin added, but this is an inference, not a proven fact. Claims that it contained quicklime, saltpetre or other specific ingredients have been argued over for centuries without agreement. It is safest to say that the weapon was real and effective but that its precise nature is unknown.
Origins and the sieges of Constantinople
A Byzantine chronicler, Theophanes, traditionally links the introduction of the weapon to an engineer named Kallinikos, said to have come from Syria around 672. The tradition is often repeated, though some historians treat the details with caution, since the chronicle was written long after the events.
What is clear is that the empire needed a new weapon. Arab forces, newly expanded across the Near East, built fleets of their own and attacked the Byzantine capital by sea more than once. The best-known attempts are the blockade of the late 670s and the large siege of 717 and 718. Byzantine sources credit fire-throwing ships with a significant role in repelling the attackers, along with the city’s land walls and a chain that could be stretched across the Golden Horn to close the harbour. The weapon was probably one factor among several, but the empire’s survival through these years is among the most consequential outcomes in the history of the Mediterranean seafaring world.
The dromon
The standard Byzantine warship in this period was the dromon, an oared galley descended from the rowed warships of late antiquity. The word is Greek and means something like “runner”. Dromons are described in the sources as having one or two banks of oars, and a fighting platform or castle for soldiers and archers. Their exact dimensions and arrangement varied over several centuries, and artists’ depictions are limited, so reconstructions involve some guesswork.
Dromons remained galleys, which meant they shared the strengths and weaknesses of earlier oared warships, including those described under trireme design. They were fast and manoeuvrable in calm water, depended on the coast, and needed large crews. Byzantine fleets generally operated close to their own coasts and islands, supported by bases and beacon systems that gave warning of approaching enemy ships.
How the fire was used
Descriptions suggest that a siphon, a pressurised tube, projected the burning liquid from the bow of a ship, and the crew aimed it at enemy vessels at close range. Because it was dangerous to the user and difficult to control, it would have required trained operators. Hand-held versions, and grenade-like pots, are also mentioned in later sources. The weapon had its limits: it relied on a short distance, calm conditions and a favourable wind direction.
The psychological effect should not be underestimated either. Enemy accounts describe fear of the fire, and part of its value may have been simply to deter attack. Byzantine writers on warfare recommended keeping its details from foreigners, and there are stories of diplomatic requests for the secret being refused.
Later fleets and decline
The Byzantine navy was not static. In its middle period it combined regional fleets with a central imperial fleet based at Constantinople, and it defended against Arab raiders, Slavic and Rus attackers, and later Italian maritime republics. In 941, according to Byzantine sources, fire-armed ships helped defeat a fleet of Rus under Prince Igor on the Bosporus approach to the capital.
Over the following centuries, the empire’s fleet weakened. The causes were financial strain, internal conflict and increasing dependence on foreign naval allies such as Venice, which could also be a rival. By the time of the Fourth Crusade in 1204, when Venetian ships helped capture Constantinople, the old dominance of Byzantine seapower was long gone. The Venetian Arsenal, a state shipyard that became a model for organised shipbuilding, shows how another city turned naval production into an institution.
Why the story endures
Greek fire is often presented as a lost super-weapon, but the better lesson may be organisational. The Byzantine state combined a small number of technical ideas with a standing navy, secure harbours and a defensible capital. The weapon helped keep the city alive in moments of crisis, and the empire survived for several more centuries. Later incendiary devices, including those used by Muslim and Crusader forces, borrowed from or competed with the same idea. The decline of Greek fire is itself unclear: knowledge of how to make it may have faded, or gunpowder weapons may have made it less useful.