Not long after our Quest for Fire men picked up the ability to burn the crap out of things . . . from a distance. The first mention of the flamethrower is in Thucydides where some Greeks burned the living tar out of some other Greeks with tubes of flame. This was in about 424 BC. The Byzantines followed a few centuries later with early air pumped flame throwers and the Chinese made some crazy fire vomiting machine.
This may be appearing in this week's Castles & Crusades game . . . .