Koriyama Castle located in Yoshida-cho, Aki Takata City, Hiroshima Pref. was a large-scale castle which covered the whole mountain of Koriyama. The original castle was built on a ridge in the southeastern part of the mountain in 1336 by Mori Tokichika, who was appointed as the Jito (an official to manage manors) of Yoshida manor. Since then the successive heads of the clan had resided at this castle until the time of Mori Motonari, who fortified the castle and expanded the castle area in the whole mountain. In the Battle of Yoshida Koriyama in 1541, the castle was attacked by Amako Haruhisa’s forces with 20,000 soldiers, but the Mori clan succeeded in beating them back. In 1589, the Mori clan shifted its bases to Hiroshima Castle. Koriyama Castle was dismantled in the early Edo period. Most of the castle compounds were destroyed at this time. At the present time, there are about 130 remains of kuruwa (castle compounds) spreading all over the mountain, from which we can easily imagine how large the castle was.