Gunpowder, reportedly produced from saltpetre, sulphur and charcoal, is a Chinese invention. Earliest records of the formula date to the 800s. The Chinese used gunpowder to propel rockets, and to produce incendiary and explosive projectiles thrown by catapult. By the 1200s, a Chinese Bureau of Munitions was operating seven factories that produced 7,000 rockets and 21,000 bombs a day. The weaponry included a so-called "thunder-crash bomb", which the Chinese unleashed in 1232 on Mongol troops besieging Kaifeng, capital of the north Chinese Jin Empire. During the later years of the 13th century, the Chinese invented cannons, using gunpowder to fire projectiles from metal barrels.

It was at around this time that the explosive first appeared in both the Islamic world and Christian Europe. In 1267, Roger Bacon produced a recipe for gunpowder. He allegedly derived his formula from a firecracker one of his friends had obtained during a visit to the Mongol court at Karakoram. Other travellers, returning from Arabia, also disseminated information about the invention and its military potential.

One of the first recorded applications of gunpowder in European military history occurred at the 1346 Battle of Crecy, where the English arsenal included little gunpowder "firepots." These had little impact on the outcome of the battle, acting merely as curious adjuncts to the English longbows that won the day. By 1350, however, Petrarch was able to make the observation that guns had become "... as common and familiar as any other kind of arms." The Ottoman Turks embraced gunpowder with enthusiasm, using it with spectacular effect during their assault on Constantinople in 1453. In preparation for the attack, Mehmet II hired a European craftsman to manufacture seven huge cannons, including one 25-ton monster that could fire stone balls almost a mile.

Cannons produced impressive noises and could inflict considerable damage on an enemy. Handguns (which first appeared in the mid-15th century) required far less training than did bows and arrows. During the 1300s and 1400s, however, these inventions remained little more than ineffectual auxiliary weapons in the Islamic and Christian West. They were, in fact, often as dangerous to their operators as to enemies. By the end of the 1400s, however, the explosive (along with related innovations such as corned gunpowder and tubular barrels) had radically altered not just the nature of warfare, but also the dynamics of cross-cultural encounters, and many aspects of European culture. One highly visible facet of material culture that changed dramatically was the architecture of military fortifications. As Machiavelli observed in 1519, artillery rendered the traditional high, thick walled edifices of feudal Europe indefensible.

The "Machina Tormentaria": Artist's Rendition of a 15th century "machine gun"