Yi Sun-Shin was born on April 28, 1545. He was noted as being intelligent at an early age and joined the military. His first combat experience was against Jurchen raiders where Yi proved himself to be a skilled strategist. However he was demoted due to jealous superiors and was put in charge of the Korean navy where he developed the Turtle Ship in anticipation of a Japanese invasion. The Japanese invaded in 1592 and quickly overran much of the Korean peninsula. However the Korean navy proved superior to the Japanese navy. Despite having no naval experience Yi decisively defeated the Japanese Navy in a series of battles that broke the Japanese supply lines. The Japanese forces quickly retreated due to lack of supplies. For their second invasion the Japanese planted a double agent in the Korean court who successfully manipulated the King into demoting and replacing Yi Sun-Shin. The Korean navy was subsequently defeated and reduced to only thirteen ships. Yi was reinstated as naval commander and in his most famous victory defeated a Japanese fleet of 300 with the remaining thirteen ships. The Japanese called off their second invasion and attempted to retreat at Noryang. A Korean-Chinese fleet intercepted them and destroyed many ships but Yi was fatally wounded in the battle.