In early 1592, at the outset of this conflict, Admiral Yi Sun-Sin, in charge of the Right Division of Chulla Province, made his headquarters in the port city of Yosu. In Yosu, he constructed his famed turtle ships. The first Kobukson was launched and outfitted with cannons only two days before the first Japanese troops landed at Pusan. In the fifth month of 1592, assisted by Admiral Won Kyun of the Left Division of Chulla Province, Admiral Yi engaged the Japanese at Okpa. In his first battle, Admiral Yi commanded 80 ships compared to the Japanese naval force of 800 ships. The Japanese were trying to re-supply their northern bases from their port at Pusan. By the end of the day, Yi had set afire 26 Japanese ships and the rest had turned to flee. Giving chase, he sank many more, leaving the entire Japanese fleet scattered.
Several major engagements followed in which Admiral Yi annihilated every Japanese squadron he encountered. Courageous and a tactical genius, he seemed to be able to outguess the enemy. In one incident, Admiral Yi dreamt that a robed man called out "The Japanese are coming." Seeing this as a sign, he rose to assemble his ships, sailed out, and surprised a large enemy fleet. He burned twelve enemy ships and scattered the rest. In the course of the battle, he demonstrated his bravery by not showing pain when shot in the shoulder. He revealed his injury only when the battle was over, at which time he bared his shoulder and ordered that the bullet be cut out.