On June 19, Yi Si-ae evacuated Bukcheong and split his army. While Yi Si-ae advanced north of Dancheon, recruiting various rebel groups and Jurchens, Yi Si-hap stationed about 20,000 soldiers in Yeoju-eul Village, near Bukcheong. He dispatched a group of 500 female rebels to attack the government forces from Gosaripo Village in Iseong County to Bukcheong Fortress. Kang Soon and his forces entered Bukcheong Fortress unaware that Yi Si-ae's army was not there, and Yi Si-hap's rebels surrounded them. At the end of the day, as suggested by Kim Gyo, Kang Soon installed palisades around the castle on the flat ground while building a trench inside the castle and dug a tunnel outside the castle to prepare for an enemy attack. On June 24, from 2 to 4 am, Yi Si-ae attacked but was stopped by Kang Soon's emplacements. As the day dawned, Yi Si-ae's army as they began to lose morale. Yi Si-ae sent a northern official to parlay with Kang Soon and offered to surrender. But Kang Soon reprimanded him, "If you are a soldier, go to the palace and surrender yourself." Yi Si-ae attacked Bukcheong ten times but could not break his defenses.
