Establishment of the Hwatong Dogam

At Choe Mu-seon’s urging, Goryeo set up an office to make gunpowder and firearms, producing eighteen kinds of weapons, including the daejanggun cannon, for use against the pirates.

The Yuan kept the making of saltpetre secret. Choe Mu-seon learned it from a Yuan man named Li Yuan, succeeded in making gunpowder and petitioned for a gunpowder office. It produced cannon such as the daejanggun, ijanggun and samjanggun, fire arrows and the juhwa rocket — eighteen weapons in all — and warships to carry the guns. Three years later they proved themselves at Jinpo.