2. Greek Fire
The next is an incendiary weapon created by the Byzantines. It was a genius invention that seemed to be before its time. As a closely guarded military secret certain details have been lost, but it was unarguably a considerable destructive force. Greek fire was simply a flammable liquid, although the exact formula has been lost, the key feature though was it would cling and some evidence suggest it would burn on water, or was indeed ignited by contact with it. It started out being used in small clay vessels which could be thrown, much like grenades. It made sense to arm ships with this stuff, so Byzantine fire ships had a boiler full of this substance that was heated and had a pump so that it could be pressurized and sprayed over enemy ships, reducing the ships and crews to ashes in very short order. That's right, shipboard flamethrowers in the late seventh century. At one point in history one possible source suggests that even the Vikings came up against a fire ship. It didn't go well for them.