Busan and marched towards Jeonju, taking Sacheon and Changpyeong along the way. Plot to dismiss Yi Sun-sin The Korean navy was again to play a crucial part in the second invasion, as in the first, by hampering Japanese advances on land by harassing supply fleets at sea. However, despite his previous successes, Yi Sun-sin was both demoted and jailed by King Seonjo, largely due to a Japanese plot to deceive the Korean court and take advantage of the court's political infighting. Government officials gave direct orders to launch a surprise naval operation against the Japanese, based on a tip from a presumed reliable Japanese spy. Yi refused to obey these orders, knowing that this was an obvious trap meant to have his own fleet sail into an ambush. This development allowed others within the court to further advance their personal agendas while Yi was severely punished. Ultimately, Won Gyun was appointed in Yi Sun-sin's place at the head of the Korean navy. Battle of Chilcheollyang After Won Gyun replaced Yi Sun-sin as head of the Korean navy, he was quick to take action and justify his newly acquired position. He gathered the entire Korean fleet, which now had more than 100 ships, outside of Yeosu, to search for the Japanese. Without any previous preparations or planning, Won Gyun then had his entire fleet sail towards Busan. After one day at sea, Won Gyun was informed of a large Japanese fleet near Busan. He decided to attack immediately, despite reports of exhaustion among the crews of his ships. At the subsequent Battle of Chilcheollyang, Won Gyun was completely outmaneuvered by the Japanese in a surprise attack. His ships were overwhelmed by arquebus fire and the traditional Japanese boarding attacks, which largely resulted in the destruction of his entire fleet. Prior to this engagement, Bae Seol (1551–1599), a naval officer who did not submit to Won Gyun's leadership, kept thirteen panokseons under his command and out of the battle, instead escaping to the southwestern Korean coast. These would form the entire fighting force of the Korean navy during the immediately following months. The Battle of Chilcheollyang was Japan's only decisive naval victory of the war. Won Gyun was himself killed by a Japanese garrison after he struggled ashore on an island following the destruction of his flagship. The victory allowed the Japanese navy to safely escort its troop ships and to support