Although the technology of i rearms and the use of those weapons in warfare were perfected largely in late medieval Europe, the Europeans did not invent the key to these advances—gunpowder. Exactly where and when this fateful material originated is still uncertain. Yet modern experts feel there is sui cient evidence to zero in on somewhere in China as the where and sometime in the 800s CE as the when. Within that time frame, an unknown individual stumbled on the fact that combining sulfur, charcoal, and potassium nitrate (saltpeter) and exposing the mixture to a l ame produced a sudden l ash or small explosion. It appears this newly invented substance—gunpowder—was i rst used to produce i recrackers, employed then as they are today in celebrations. h e Chinese also found gunpowder could be used ef ectively on the battlei eld. h ey created small rockets that shot upward and exploded in the air, frightening enemies who were unfamiliar with them. In addition, descending rockets sometimes set the roofs of houses on i re. Another military application was a bamboo tube that discharged a burst of i re and smoke when someone touched a l ame to some gunpowder packed inside. h e Chinese also developed grenade-like weapons, the general name of which translates roughly as “thunderclap bombs.” When they exploded, they apparently generated a l ash of light and a very loud noise, which scared enemy soldiers and horses. A twelfth-century Chinese commander named Li Kang recalls in a political memoir, “At night the thunderclap bombs were used, hitting the lines of the enemy well, and throwing them into great confusion. Many l ed, howling with fright.”40 h ere is no evidence, however, that any of these early Chinese gunpowder devices produced explosions powerful enough to destroy units of soldiers or stone walls.