On April 13, 1592, the Japanese army launched a massive invasion.
Siege of Busanjin and
Siege of Dongae quickly fell under overwhelming force. Because of the overwhelming disparity in war preparations between Joseon and Japan, Joseon forces suffered continuous defeats from the very beginning. Local officials fled, commoners took refuge in the mountains, and towns were left deserted. Gyeongsang Left Army Commander
Yi Gak abandoned the defense of Dongnae fortress and fled, while Gyeongsang Left Naval Commander
Park Hong failed to rally his fleet and abandoned his base. Won Gyun also resented Yi Sun-sin personally. He was five years older and had seniority, but Yi was promoted above him. When Yi was appointed Commander-in-Chief of the Three Provinces Navy in late 1593, becoming Won Gyun's superior, Won's bitterness deepened. Although many in the court, including King Seonjo and high-ranking officials such as
Yun Du-su and
Yun Geun-su, praised Won Gyun as brave and useful, Yi's mistrust grew. Eventually, Won Gyun was reassigned as Commander of Chungcheong Province, effectively removed from the navy. As Chungcheong Commander, he was impeached for corruption and brutality, but Seonjo shielded him, valuing his martial talent. Even in these posts, he submitted several proposals for naval operations to the court. Later, when
Yi Mong-hak’s rebellion broke out in 1596, Won Gyun was again entrusted with high command, showing Seonjo's continuing trust in him. Seonjo increasingly doubted Yi Sun-sin, accusing him of inaction, while praising Won Gyun as diligent and fearless, though others warned he lacked the ability to command. Still, Seonjo favored him as a potential replacement for Yi. By late 1596, peace negotiations had collapsed, and another invasion (Jeongyu War) was imminent. Pro-war ministers including Yun Du-su and Kim Eung-nam pushed for Won Gyun's reinstatement. Misled by Japanese misinformation about Katō Kiyomasa's crossing, the court blamed Yi Sun-sin for failing to intercept, and Seonjo used the incident to arrest Yi and replace him with Won Gyun.
Defeat at Chilcheollyang As Commander-in-Chief, Won Gyun rejoiced at Yi's downfall but lacked strategic vision. Though brave in personal combat, his reckless nature made him a poor leader. He quarreled with subordinates and failed to maintain discipline. Forced into battle by court pressure, Won Gyun led the fleet into several costly encounters in mid-1597, suffering attrition and loss of ships. Finally, on July 14–16, his fleet of over 100 ships was caught by surprise at Chilcheollyang by a massive Japanese force. Exhausted, poorly disciplined, and unprepared, the Joseon navy collapsed. Most ships and men were destroyed including
Yi Eok-gi (Naval Commander of Jeolla Right Province) and
Choi Ho (Naval Commander of Chungcheong Province). Wŏn was considered to be killed in action at Chuwonpo while running away, when his brother was killed during this battle. He was 57 years old. From over 130 warships and 13,000 men, only the small detachment of twelve warships under the command of admiral Pae Sŏl – who refused to participate and fled even before the battle began – survived. Every other ship in the combat was destroyed or disabled, along with almost all of the Joseon navy line officers and many capable mid-level commanders. The battle opened the route for the Japanese to advance to the Yellow Sea threatening Jeolla Province directly, and Todo devised a plan to attack
Hanyang from land and sea with Katō Kiyomasa and Konishi Yukinaga. However, Japan's hopes were crushed again by Yi Sun-sin's return at the
Battle of Myeongnyang, which would decide the winner of the devastating war. == Legacy ==