Napalm was an invention of 20th-century warfare, but the deadly incendiary substance had an ancient and mysterious ancestor. Greek fire, developed in the Byzantine Empire of the seventh century, was a devastating weapon capable of being fired through tubes like a flamethrower, or hurled grenade-style in pots. It stuck to and burned everything, and couldn’t be doused by water, making it especially useful in naval battles.
In the AD 670s, the Byzantines repelled an Arab fleet attacking Constantinople with siphons mounted to their ships – the beginning of its dominance in its arsenal, which helped the empire survive until the 15th century. But then Greek fire disappeared.
After being created, supposedly by a Jewish refugee called Callinicus of Heliopolis, its ingredients became a state secret. The recipe was eventually lost. While petroleum, naphtha, quicklime and sulphur are educated guesses, the exact composition of Greek fire remains unknown. That’s probably for the best.