Byzantine forces certainly loved roasting their opponents, but why not use their flames where it's least expected? That's right, the Byzantine Empire had its navy forces equipped with incendiary weapons that would set enemies ablaze. Men on board would hold siphons (early versions of flamethrowers) and take pleasure in burning their enemies, helping them sink to the bottom of the sea. This weapon was so effective that ships would continue to burn even under water. In fact, the Byzantine were able to fend off Muslim forces with Greek fire and saved Constantinople in 672 AD.