Battle of Motobuto Castle
Dates: Eiroku 11 (1568); Genki 2 (1571)
Location: Motobuto Castle on Kojima – an island in the Seto Inland Sea that was part of Bizen Province
Synopsis: The first battle between the Murakami and the Kōzai (backed by the Miyoshi) was resolved through mediation by the Ōtomo clan. In the second battle, Kobayakawa Takakage (the third son of Mōri Motonari) toppled the castle defended by the Murakami (backed by the Uragami).
Motobuto Castle was the site of multiple battles owing to its strategic location on Kojima between Shikoku and Honshū. The first conflict, occurring in 1568, was waged between the Murakami and the Kōzai clans (backed by the Miyoshi) and settled through mediation. The second conflict occurred in 1571 between the combined forces of the Murakami and Uragami against the Mōri. Although details of these conflicts are scant, the records highlight the complex and shifting alliances between and among the clans vying for power in the vicinity of the Seto Inland Sea, including the Murakami (who were famous for their navy), in addition to (i) the Hosokawa, the Miyoshi, the Kōzai and the Shinohara from provinces in Shikoku, (ii) the Mōri, the Uragami, the Ukita, the Nose, and the Mimura from provinces in Honshū, and (iii) the Ōtomo and the Bessho from provinces in Kyūshū.
During the Muromachi period, Kojima was a separate island that served as a gateway from Awa and Sanuki provinces in Shikoku to Bizen Province on the main island of Honshū. Although Kojima was a part of Bizen Province, the island was controlled by the Hosokawa clan who served as the military governors of Awa and Sanuki provinces. During the latter part of the Eiroku era (1558 to 1570), a majority of Kojima was governed by Mimura Iechika after he nearly unified Bitchū Province by joining forces with Mōri Motonari who held Bingo Province,
First battle at Motobuto Castle
Motobuto Castle stood as an impregnable fortress on the western shores of Kojima, protected by the sea and mountainous terrain. In 1568, a conflict arose at Motobuto Castle between the Kōzai clan (kokujin, or provincial landowners, in Sanuki) and Murakami Takeyoshi of the Murakami navy of Nōshima. On the side of the defenders, a retainer of the Murakami named Shima Yoshitoshi killed Kōzai Matagorō.
After counterattacks initiated by the Kōzai clan with the backing of the Miyoshi placed them in difficult circumstances, the Murakami settled with the Kōzai through the mediation of the Ōtomo clan. Having made contributions as a messenger, Shima Yoshitoshi became the lord of Motobuto Castle. From around this time, Murakami Takeyoshi established friendly relations with the Ōtomo and Miyoshi who were enemies of the Mōri clan.
Developments in Bizen Province
In Bizen, while Uragami Munekage expanded his base of power, his retainer, Ukita Naoie, assassinated Mimura Iechika. In 1567, at the Battle of Myōzenji, Naoie defeated Iechika’s son, Mimura Motochika and, in 1568, decimated the Matsuda clan of Bizen. In 1569, after Naoie separated from the Uragami, Munekage subdued him and became a daimyō in control of most of Bizen, in addition to portions of Mimasaka, Bitchū, and Harima provinces.
In the tenth month of 1569, Munekage colluded with Ōtomo Yoshishige and Amago Katsuhisa to oppose the Mōri clan. Mōri Motonari and the Mimura found themselves surrounded, in conflict with not only the Uragami (in Bizen), the Ōtomo (in Bungo and Chikugo), and remnants of the Amago clan (in Izumo), but also the Miyoshi (in Awa and Sanuki), the Miura (in Mimasaka), and the Yamana (in Hōki and Inaba). In the tenth month of 1570, Munekage joined with the Miyoshi clan in opposition to Oda Nobunaga and Motonari to attack Miki Castle in Harima. That same month, Ukita Naoie also came into conflict with the Mōri and attacked Kōzan Castle in Bizen.
Second battle at Motobuto Castle
In the second month of 1571, Murakami Takeyoshi combined with Munekage and separated from the Mōri family. Kobayakawa Takakage immediately gathered troops with the intention to capture Motobuto Castle, and, in the fourth month, Motobuto Castle fell.
At this time, the Shinomiya clan (a kokujin from Hibi on the Kojima Peninsula) along with Kōzai Mototoshi of Sanuki, joined with Kobayakawa Takakage and landed in Kojima. Mototoshi attacked Kaya Castle and his retainer, Uematsu Yukimasa, killed Yoshida Uemon-no-jō who led the castle garrison. However, after next attacking Motobuto Castle, Mototoshi was killed in the midst of a fog-enshrouded battlefield.
Battle between the Mōri and the combined forces of the Miyoshi and Ukita clans
In the fifth month of 1571, Shinohara Nagafusa, a senior retainer of the Miyoshi family, responded to appeals from Uragami Munekage and Ukita Naoie to lead naval forces from Awa and Sanuki to attack Kojima. Kobayakawa Takakage assigned soldiers to Awaya Narikata and sent them to Kojima as reinforcements. In the ensuing battle, however, the Mōri suffered a bitter defeat to the Uragami army and the forces led by Shinohara Nagafusa who swiftly arrived as reinforcements. In Bitchū, Shō Katsusuke occupied the base of the Mimura clan at Matsuyama Castle and colluded with Ukita Naoie, and, at the same time, Ukita forces invaded the Mimura territory and recaptured Kōzan Castle.
During this time, attacks tied to the encirclement of the Mōri intensified while Mōri Motonari laid ill. Motonari then dispatched Ankokuji Ekei as a messenger to meet Ashikaga Yoshiaki in Kyōto and to request assistance in forging a settlement with the Ōtomo, the Uragami, and the Miyoshi. However, Yoshiaki rejected a settlement involving the Miyoshi so the proposal failed. On 6/14 of Genki 2 (1571), Motonari died before Ekei returned, and the clan was inherited by his eldest grandson, Mōri Terumoto.
In the ninth month, an armed clash occurred again at the Saita Castle in Bitchū between the combined forces of the Uragami and Ukita who served as reinforcements for Ueki Hidesuke (Hidenaga’s son) and the combined forces of the Mōri and Mimura, but the Uragami and Ukita prevailed while the elder son of Mimura Motochika, Shō Motosuke, was killed in battle. Motobuto Castle was granted to Nose Yoriyoshi, a retainer of the Ukita.
Demise of the Mimura and separation of the Ukita from the Mōri clan
At the end of 1573, Munekage reconciled with Bessho Nagaharu through the devices of Nobunaga, whereupon Munekage received a letter from Nobunaga recognizing Munekage’s governance of Bizen, Harima, and Mimasaka provinces. At this point, Munekage surpassed his former lords, the Akamatsu, earning a status equivalent to his former role of military governor, and realized the peak years of prosperity for the Uragami clan. In the third month of 1574, Ukita Naoie separated from Munekage, and allied with the Mōri. Indignant at this outcome, Mimura Motochika separated from the Mōri and joined forces with Munekage.
In the fifth month of 1575, Matsuyama Castle fell to an assault by the Mōri clan and Mimura Motochika killed himself. In the sixth month, Tsuneyama Castle in Kojima defended by Ueno Takanori (the son-in-law of Mimura Iechika) was also toppled and the Mimura clan eliminated in the Bitchū Conflict. In the ninth month, Ukita Naoie captured Tenjinyama Castle defended by Uragami Munekage, causing Munekage to flee for safety to the Kyōto area in an event known as the Siege of Tenjinyama Castle.
In the tenth month of 1579, Ukita Naoie separated from the Mōri family and pledged allegiance to Oda Nobunaga. At the end of 1581, Naoie died of illness at Okayama Castle. In the second month of 1582, a battle broke out between the Ukita clan and the Mōri clan at Hachihama in the Kojima District of Bizen in which Ukita Motoie was killed in action. The Ukita forces fled in defeat, but, owing to the valorous acts of the Seven Spears of Hachihama (including Nose Yoriyoshi, the lord of Motobuto Castle), the Mōri forces were narrowly stopped. Ukita forces holed-up in Hachihama Castle, leading to the Battle of Hachihama. Motobuto Castle remained until 1580. The timing of its abandonment is uncertain.