Yi Il was born in 1538. In 1558, Yi passed the military examination and served as Naval Commander of Left Jeolla Province. In 1583, when Nitangjie and the Wild Jurchens rebelled against the Joseon government in Kyongwon County and Jongseong, Yi was assigned magistrate of Kyongwon and repelled the rebel forces. In 1586, as Nitangjie rebelled again in Hoeryong, Yi had swept base of rebel forces as magistrate of Hoeryong and Yi became Army Commander of Hamgyong Province in recognition of his contribution. Yi also expended Jeseungbangryak, the book on military strategy in the Joseon dynasty. In 1587, when he was Commandant of Hamgyong Province, He detainedYi Kyung-rok, magistrate of Kyonghung and Yi Sun-sin, Subarea Commander of Chosan, holding them responsible for losing battle after being ambushed by the Jurchen while harvesting at Noktundo. Later, Yi attacked Jurchen in revenge for their invasion. In the attack, Yi killed about 380 soldiers of Jurchen and burnt about 200 houses. In 1588 and 1589, Yi discussed national defense in frontier with Shin Rip and Jung Eon-sin as Commander of Army Commander of Jeolla Province. In 1592, when the Imjin War occurred, Yi was Mobile Border Commander. On 24 April 1592, Yi fought against Japan at the Battle of Sangju. Yi organized a unit about 800 soldiers but they were unstructured. Yi started to train with the rest of them on 25 April. They were defeated by Japan being ambushed. Yi had run off to Chungju and met Shin Rip. Shin Rip tried to kill Yi taking responsibility for the defeat, but Yi wasn't killed because Kim Yeo-mul stopped Shin Rip. Yi participated in Battle of Chungju with Shin Rip and he was defeated and pulled back to Pyongan Province once again. Yi contributed to recapturePyongyang with forces of Ming by winning Siege of Pyongyang on 8 January 1593. Later, he had trained the forces and when Hanyang was recaptured and the Military Training Agency was founded, he became the Police Chief of the Right and concentrated on training soldiers as the Left Initiate. Yi settled the rebellion of Song Yu-jin as Mobile Border Commander. In 1601, Yi died in Chongpyong while he was being transported on the suspicion of murder.
