Thunderclap Bomb

The thunderclap bomb, or zhen tian lei, is an early Chinese gunpowder bomb consisting of a cast-iron shell packed with gunpowder, used by Jin dynasty and later Song dynasty forces during the Mongol invasions of the thirteenth century, historically significant as one of the earliest documented uses of a metal-cased explosive weapon rather than the ceramic or bamboo incendiary bombs used previously in Chinese warfare. The Jinshi, the official Chinese historical record of the Jin dynasty compiled in the following Yuan period, describes the weapon being dropped or lowered by chain from city walls during the Mongol siege of Kaifeng in 1232, with an explosion loud enough to be heard for tens of kilometers and an iron casing whose fragmentation the account describes as capable of piercing armor. The thunderclap bomb sits historically between earlier gunpowder incendiary devices and later true fragmentation grenades and shells, marking a documented step in the shift from gunpowder used mainly for flame and noise toward gunpowder used for shrapnel and blast effect.