[1] He served as the Provincial Army Commander or byeongma dojeoljesa (병마도절제사; 兵馬都節制使) of Hamgil Province from 1450 until 1453.
As a former subordinate of Kim Chongsŏ who was killed by his political rival Grand Prince Suyang (the future King Sejo), Yi was recalled by Grand Prince Suyang-controlled royal court who tried to replace him with Pak Ho-mun (박호문; 朴浩文) in 1453.
However, Yi killed his new replacement and rose up in rebellion.
He attempted to gather Jurchen support for his rebellion by declaring himself the emperor of the Geum dynasty (대금; 大金), a revival of the Jurchen Jin.
He wanted to establish the new dynasty's capital at Wuguocheng (Korean: 오국성; Chinese: 五國城), but was killed in Jongseong [ko] by his subordinates, Chŏng Chong (정종; 鄭種) and Yi Haeng-gŏm (이행검; 李行儉) before he could cross the Tumen River.