Chinese alchemists accidentally discovered gunpowder in the late Tang dynasty by mixing saltpeter, sulfur, and charcoal. Gunpowder was used for military purposes, such as cannons and grenades, and for non-military purposes, such as fireworks. The Song Dynasty repelled Mongol invaders with “flying fire” arrows and advanced gunpowder-based weaponry. Gunpowder remained a secret weapon until the […]