Imjin War

In 1503, Joseon developed cupellation — a technology to extract silver from lead ore — which was transmitted to Japan. Japan went on to produce 30% of the worlds silver, using this wealth to build national power, which ultimately returned as the Imjin War.

During the Imjin War, Mozambican soldiers served under the Ming dynasty. Called "Sea Ghosts," they dove underwater to puncture holes in Japanese warships. The Annals of the Joseon Dynasty recorded them as having "faces black as lacquer, lurking beneath the sea."