[3] The initial phase of the campaign began in 19 July 1540 (15th day of 6 month of Tenbun 9), which involved an attack by the troops of Amago Hisayuki, his son Masahisa and his nephew Kunihisa on the domain of Motonari's ally, the Shishido clan, a foray that was to prove of little effect except to deny Haruhisa of some of his most capable generals and soldiers for the attack on Koriyama Castle.
[2] In August Amago Haruhisa had gathered a force of 30,000 and departed Izumo Province, moving into the vicinity of Motonari's Yoshida-Koriyama Castle and establishing a headquarters nearby.
The castle itself was defended by around 3,000 soldiers, by which time urgent requests for aid were dispatched to the Ōuchi in Suo Province.
The Ōuchi relief army, consisting of 10,000 men led by Sue Harukata,[2] finally departed Suō Province in the 11th month (corresponding to December 1540 in Tenbun 10), pausing on Miyajima to offer prayers for victory at the Itskushima Shrine before landing in Aki and marching towards Koriyama Castle.
In the wake of this fight, the Amago retainers, noting the army's dwindling supplies and poor morale, elected to retreat.