Gunpowder is the first physical explosive and propellant. Prior to its invention, many incendiary and burning devices had been used, including Greek fire. The invention of gunpowder is usually attributed to Chinese alchemy, and is popularly listed as one of the "Four Great Inventions" of China. It was invented during the Tang Dynasty (9th century), and the earliest record of a written formula appeared in the Song Dynasty (11th century). Knowledge of gunpowder spread throughout the Old World as a result of the Mongol conquests of the 13th century. It was employed in warfare to some effect from at least the 14th century, although the development of effective artillery took place during the 15th century, and firearms came to dominate early modern warfare in Europe by the 17th century.