Around the year 850 CE, Chinese alchemists were trying to brew a magical “elixir of life” that would let people live forever. They mixed a bunch of chemicals together, including saltpeter, sulfur and charcoal. Instead of granting eternal life, the mixture made a sudden bright flash and a loud bang. They had accidentally invented gunpowder.
At first the Chinese mostly used gunpowder for entertainment. They packed it into bamboo tubes to make some of the earliest fireworks, signal rockets and noise-makers used at festivals. It took another 200 years before someone realized you could use it as a weapon - first as fire arrows, then in primitive bombs, then in early cannons by the 1100s.
Gunpowder eventually spread west to the Middle East and Europe by the 1200s. It completely changed warfare. Castles built to keep out arrows and battering rams couldn’t survive cannons. Knights in plate armor couldn’t survive bullets. Within a few hundred years, an Asian accident in a search for immortality had rewritten how the whole world fought wars.
