Divers found medieval Mongol bombs in a shipwreck off Japan
When Mongol fleets attacked Japan in the 13th century, they brought thunder-crash bombs: iron shells packed with gunpowder. Centuries later, underwater archaeologists recovered some from a wreck off the Japanese coast, and X-rays confirmed they still held powder. The finds back up Chinese chronicles describing the earliest explosive bombs.
Bombs were born in East Asia. Around 1000 AD a soldier named Tang Fu won a generous reward for demonstrating gunpowder pots that spewed fire, and a military manual of 1044, the Wujing Zongyao, lists devices with vivid names such as the thunderclap bomb. These early weapons had soft casings and worked mainly as incendiaries rather than true explosives.
Cast-iron shells filled with gunpowder emerged in 13th-century China. A Jurchen Jin army used explosive bombs against a Song city in 1221, and the name thunder crash bomb seems to date from a naval battle with the Mongols in 1231. A later history describes the defence of Kaifeng in 1232, when such a bomb reportedly boomed like thunder over thirty miles away and could pierce iron armour. Production grew enormous: in 1257 the Song official Li Zengbo wrote that one arsenal was turning out one to two thousand iron shells a month.
An explosion does its damage in several ways. The shock wave has two parts, a positive pulse pushing outward and a negative phase drawing back as the pressure bubble collapses, and distance offers the best protection. Heat from a blast can reach 2,480 degrees Celsius in military tests but usually travels less far than the shock or the fragments. Deliberate fragmentation, using iron pellets and broken porcelain, is described as early as the 14th century in the Ming text Huolongjing.
Fragments can be startlingly large. When the ship SS Grandcamp exploded in the Texas City disaster of 16 April 1947, its two-ton anchor was hurled nearly two miles inland, burying itself in a refinery car park. The word bomb comes, via Latin, from the Greek bombos, imitating a booming or buzzing sound.
Source: Bomb
