7 China Develops Gunpowder Weapons c.1100 CHINESE ALCHEMISTS discovered the recipe for gunpowder--saltpeter, sulfur and charcoal--in the 9th century. But the great development of gunpowder weapons began in the early 1100s when the Song dynasty was besieged by the Jurchen Jin Tatars. Over the next 200 years, as the Jin conquered northern China and were in turn overrun by the Mongols, an arms race raged between defenders and invaders. Bamboo flamethrowers evolved into metal-barreled guns. Paper incendiary grenades gave way to iron bombs that shattered stone walls. When gunpowder technology reached Europe--it was first used at the siege of Metz, now in France, in 1324--the effect was explosive. Since only kings could afford large numbers of muskets and cannons, the nobility's power declined. Centralized states, backed by standing armies, replaced feudal fiefdoms. Guns gave colonizers a big advantage over native peoples. But the spread of such weapons eventually leveled the field--making possible an age of revolutions, world wars, guerrilla conflicts and terrorist bombings.