After the Japanese invasion of Korea in 1592, Yi Gwang-gwan and Kwokyeong, a Joseon patrol in Jeolla Province, joined the army of some 40,000 people.

He was dismissed for summary disposal of fugitives after earning his degree in the field, but was re-appointed as a judge of the Han family and was appointed as a military officer in 1596.

Afterwards, he attempted to attack the Japanese troops stationed in Yegyo Bridge in Suncheon, but failed due to the uncooperative efforts of the Ming Dynasty men who were reluctant to expand the war.

He was a general who conducted the military for seven years during the Japanese Invasion of Korea in 1592, and earned a major in history along with korean Admiral Yi Sun-shin of the sea.

[citation needed] When the Japanese forces invaded Korea in 1592, Kwŏn was appointed the mayor of Gwangju, Jeolla province and given the military command of the region.

Kwŏn supervised his unit by executing deserters personally, and his vanguard commander Hwang Jin (황진; 黃進) kept fighting despite a gunshot injury.

Japanese forces led by Ukita Hideie laid siege to the fort for one month, and Kwŏn's army was running out of water supplies.

After the war, the king Seonjo built a monument on the top of Doksan named Semadae (세마대; 洗馬臺), "the place where horses were washed", as a tribute to Kwŏn.

Threatened by this action, Japanese commanders Katō Kiyomasa and Ukita Hideie, attacked Haengju fortress with 30,000 men, trying to finish off Kwŏn's troops once and for all.

The Japanese, with over 10,000 casualties and top generals Ukita, Ishida Mitsunari, and Kikkawa Hiroie wounded, were compelled to retreat and fled the region.