Another noteworthy aspect of Korea’s heavy fire-arms is that they were not all invented to meet the sudden emergency of war. These weapons in fact made their appearance some 200 years prior to Japanese invasions of Korea (1592–98). Thanks to the efforts of Choe Museon, a general and a chemist, Korea began manufacturing and developing gunpowder and powder-based weapons. Korean cannons first saw action in 1380 against a large fleet of Japanese pirate ships, and were found to be a great success.