The Seven-year War, from 1592 to 1598, laid waste to the whole Korean peninsula. Hardly a building still stands in Korea that predates the Hideyoshi invasions except for a few stone structures. Rare and valuable collections of books were destroyed, including the official records of the reigns of the Joseon Dynasty. A series of famines, epidemics, peasant revolts, and a full-scale renewal of political squabbling in the Korean government followed on the heels of the war. As a result, culture and government were left in chaos and the social system of the country was disrupted.
For all its disastrous aftermath, the war did provide Korea with one of its most celebrated national heroes, Admiral Yi Sun-Sin. Known primarily as an inventor of the world's first iron-plated vessel and a master naval tactician, Yi also had other accomplishments. Some of his little-known inventions included the use of a smoke generator in which sulfur and saltpeter were burned, emitting great clouds of smoke. This first recorded use of a smoke screen struck terror in the hearts of superstitious enemy sailors, and more practically, it masked the movements of Admiral Yi's ships.
Another of his inventions was a type of flamethrower that was a small cannon with an arrow-shaped shell that housed an incendiary charge. This flamethrower successfully set afire hundreds of enemy ships. Along with his inventions, specific tactical maneuvers demonstrate Yi's brilliance as a naval tactician, such as his use of the fishnet formation and using two-salvo fire against ships.