As an incendiary weapon of choice for fighters in the Byzantine Empire, Greek fire was first used during the 670s. The flammable liquid burned on water, making it inextinguishable and highly effective in naval combat. While Greek fire wasn't the first such weapon used in history, the exact composition of the Byzantine version remains unknown. Called "artificial fire," it was sprayed on enemy ships, bringing with it flames and smoke alike. Greek fire may have been a mixture of sulfur and quicklime or saltpeter, but historians continue to debate its true make-up.