Izushi Castle

Izushi Castle (Japanese: Izushi-jō) is located in present-day Izushi Town, Toyooka City, Hyōgo Prefecture, Japan. It was once an important castle in Izushi District, Tajima Province, and served as the administrative center of the Izushi Domain during the Edo period. Surviving remains include stone walls, moats, and the Shinkorō Clock Tower, while several gates, bridges, and corner turrets have been reconstructed. The castle site is currently designated as a Historic Site of Toyooka City and, together with Arikoyama Castle on the mountain above, was selected as one of the Top 100 Continued Japanese Castles.

The early political center of the Izushi region was not located at the present site of Izushi Castle. During the Muromachi period, Yamana Tokiyoshi, the military governor of Tajima Province, constructed Konosumiyama Castle north of Izushi Shrine and established it as the principal stronghold of the Yamana clan. In 1569, the castle was captured during Hashiba Hideyoshi’s military campaign in Tajima on behalf of Oda Nobunaga. The castle lord, Yamana Suketoyo, temporarily lost his territory, but later reconciled with the Oda clan through the mediation of the merchant Imai Sōkyū and was allowed to return to Tajima.

In 1574, Yamana Suketoyo constructed a new fortress on Mount Arikoyama, approximately 3.5 kilometers south of Konosumiyama Castle and rising 321 meters above sea level. He relocated his main residence to the new Arikoyama Castle. A residential compound and provincial administrative offices were established at the foot of the mountain, and a castle town gradually developed around them. The Yamana clan later chose to support the Mōri clan and was attacked again by Hashiba Hideyoshi in 1580. After Arikoyama Castle fell, the Yamana clan’s rule over Tajima as a Sengoku-period daimyō came to an end.

Arikoyama Castle was subsequently administered by appointed governors. Maeno Nagayasu entered the castle in 1585, followed by Koide Yoshimasa in 1595. During the Battle of Sekigahara, the Koide family divided its loyalties in order to ensure its survival: Yoshimasa joined the Western Army, while his younger brother Koide Hideie supported the Eastern Army. Because Hideie distinguished himself in the conflict, Yoshimasa was not punished after the war, and the Koide family retained control of Izushi.

In 1604, Koide Yoshihide discontinued the principal mountaintop enclosures and the castle keep function of Arikoyama Castle. He rebuilt the residential compound and enclosures at the foot of the mountain and officially registered the new fortress with the shogunate under the name Izushi Castle. From the lower ground upward, the castle was arranged in a series of stepped enclosures consisting of the Sannomaru (Third Bailey), Lower Enclosure, Ninomaru (Second Bailey), Honmaru (Main Bailey), and Inari-maru. The lower section was surrounded by moats, while the lord’s residence and castle town were also reorganized during this period, gradually creating the street layout that survives in modern Izushi.

The former Arikoyama Castle on the summit was not extensively dismantled. Instead, it gradually fell into ruin after it was no longer used and eventually became covered by forest. Following the enforcement of the One Castle per Province Edict, Izushi Castle became the only officially retained castle in Tajima Province.

During the Edo period, Izushi Castle served as the administrative center of the Izushi Domain. In 1696, Koide Fusatsugu died at the age of three, and the Koide family was dispossessed because it lacked an heir. Matsudaira Tadachika then entered the castle. After the Matsudaira family was transferred elsewhere in 1706, Sengoku Masaakira became lord of Izushi. The Sengoku clan continued to govern the domain until the Meiji Restoration and the abolition of the feudal domain system. During the late Edo period, the domain was shaken by the Sengoku Disturbance, which arose from conflicts among retainers and financial difficulties.

During the Meiji period, Izushi Castle was dismantled under the government’s castle abolition policies, and most of its buildings disappeared. However, the stone walls, moats, and Shinkorō Clock Tower survived. In later years, the corner turrets, Tojōmon Gate, and Tojō Bridge were reconstructed, while the area around the moat was developed as Tojōbashi Riverside Park, becoming one of the principal sightseeing areas of the former castle town.

The Shinkorō Clock Tower, standing in front of the castle ruins, is one of the most recognizable landmarks of modern Izushi. It was originally built as a drum tower used to announce the time and was later fitted with a clock. Together with the castle ruins, stone walls, and surrounding traditional streets, it forms the historic townscape for which Izushi is known today.

In 1968, the Izushi Castle ruins were designated as a Historic Site of Toyooka City. In 2017, Izushi Castle and Arikoyama Castle were jointly selected as No. 162 of the Top 100 Continued Japanese Castles. Today, visitors can examine the stone walls and enclosure layout of an early modern castle before following the mountain trail to the remains of Arikoyama Castle, gaining a clear understanding of how the Izushi region developed from a medieval mountain fortress into an Edo-period hirayama-style castle town.