Greek fire was the most devastating weapon in the Eastern Roman empire. But what was it?

An image from an illuminated manuscript, the Madrid Skylitzes, shows Greek fire in use. Wikimedia

Before modern weapons of mass destruction, there was Greek fire (ignis graecus). This was the term medieval Crusaders applied to Byzantine (Eastern Roman) incendiary weapons famously used in naval combat in the Eastern Mediterranean from around 673 CE to at least the 1180s.

So secret was the recipe for Greek fire that it died with the Byzantine Empire, which fell to the Ottoman Empire in May 1453.