Battle of Oshikibata
Year: 6/5 of Tenbun 23 (1554)
Location: Mount Oshikibata in the Saeki District of Aki Province
Outcome: Sue Harukata dispatched an army led by Miyagawa Fusanaga to amass on Mount Oshikibata in Aki to confront the Mōri forces at Sakurao Castle. After a multi-directional attack devised by Mōri Motonari, the Sue army and their allies collapsed in disarray while Fusanaga perished.
The Battle of Oshikibata occurred on 6/5 of Tenbun 23 (1554) on Mount Oshikibata in the Saeki District of Aki Province. The battle was waged between Mōri Motonari of Aki and Sue Harukata of Suō Province. In this conflict, Miyagawa Fusanaga led the Sue forces on the battlefield on behalf of Harukata. This may be viewed as a preliminary clash to the Battle of Itsukushima and is also referred to as the Battle of Akashiguchi. Theories concerning the date of the battle and whether the Battle of Oshikibata and the Battle of Akashiguchi were in fact the same event are described below. In any event, this battle occurred shortly after the Separation of Suō and Aki by which Motonari severed relations with the Sue and Ōuchi clans, bringing to an end a long period of subservience and triggering armed conflict between the Mōri and their former lords.
In 1551, at the time that Ōuchi Yoshitaka was killed in a rebellion by a senior retainer, Sue Takafusa (Harukata), the Mōri clan was subservient to the Ōuchi. Yoshitaka was the father-in-law of Motonari’s eldest son, Mōri Takamoto, who advocated for the overthrow of the Sue to avenge the death of Yoshitaka. Motonari, however, refrained from action based on the realistic assessment of the difference in power between the clans. The theory that Motonari was, around this time, already looking for an opportunity to become independent of the Ōuchi cannot be substantiated by primary sources and was therefore a likely embellishment from later eras. Instead, Motonari acted in concert with the rebellion by sweeping up all of the elements opposed to the Sue in Aki with the aim of growing his power in alignment with Harukata. Thereafter, the Mōri maintained a subservient relationship with the Ōuchi and Sue clans but, owing to their expanding influence, gradually became a subject of concern for Harukata.
In the tenth month of 1553, Yoshimi Masayori, the lord of Sanbonmatsu Castle (later known as Tsuwano Castle) in Tsuwano in Iwami Province who had a debt of gratitude toward Yoshitaka, rebelled against Harukata. The third month of 1554 marked the beginning of a campaign by the Ōuchi and Sue armies to eliminate Yoshimi in an event known as the Siege of Sanbonmatsu Castle. Preceding this event, the Mōri were requested by both Yoshimi and the Sue to join their side in the conflict. Motonari may have considered participating on behalf of the Sue, but Takamoto strongly opposed the idea, resulting in a split of opinions within the family. After becoming impatient with the indecision, it was learned that Harukata made written demands directly to the kokujin in Aki who were under the command of the Mōri to deploy for battle whereupon, before long, Motonari decided to separate from andto operate independently of the Ōuchi clan.
There is a theory that Yoshimi Masayori rebelled after making a secret pact with Motonari, but, in the beginning, it is understood that Motonari had decided to participate on behalf of the Sue army and that there was no consensus of opinion within the family on the course of action. Accordingly, this theory appears to be an embellishment from later eras drawing from the outcome of events.
Course of events
According to traditional theory, the Battle of Oshikibata occurred on 9/15 while the Battle of Akashiguchi occurred earlier on 6/5 of Tenbun 23 (1554).
On 5/12 of Tenbun 23 (1554), in just one day, the Mōri army captured four castles and Itsukushima. On 5/15, the army invaded Suō and clashed with the Sue army at Kose and Misho in the Kuga District. Furthermore, on 6/5, the Mōri defeated the Sue army which had attacked Akashi in the Saeki District of Aki in an event known as the Battle of Akashiguchi.
By the ninth month of 1554, the Mōri successfully occupied Nōmishima (the island of Nōmi) in Aki and established their main base at Sakurao Castle facing the Seto Inland Sea and across from the Itsukushima Shrine. Taking account of these developments, Harukata reconciled with Yoshimi Masayori to enable him to focus on eliminating the Mōri. Faced with dwindling provisions, the Yoshimi army had no choice other than to settle with Harukata. At the beginning of the same month, Harukata assigned 3,000 troops to his retainer named Miyagawa Fusanaga and had them take the lead. While en route, a contingent of 4,000 men including Kōda Tango-no-kami and ikki forces from Yamashiro in Suō converged with them. On 9/14, a total of 7,000 soldiers amassed on Mount Oshikibata overlooking Sakurao Castle.
Meanwhile, Shishido Takaie and Fukubara Sadatoshi of the Mōri army engaged in reconnaissance. During these operations, the scouts mistakenly believed that Sue Harukata himself was leading the enemy forces, and, upon hearing this news, Motonari made plans for a surprise attack to annihilate them. On the evening of the fourteenth, the entire Mōri army at Sakurao Castle comprised of 3,000 soldiers deployed. Based on a plan to attack the enemy forces on Mount Oshikbata under cover of darkness and from all directions, Motonari and Takamoto led forces from the east, Kikkawa Motoharu (Motonari’s second son) led from the north, Kobayakawa Takakage (Motonari’s third son) led from the south, and the Shishido and Fukubara forces attacked from the west behind the enemy position. Motonari planned for an early morning assault, but the Miyagawa forces had also taken up hidden positions in the event of a surprise attack. However, after Motonari noticed a disturbance among a swarm of fireflies, his men detected the Sue soldiers laying in ambush and sent down a unit of Shishido and Fukubara soldiers. In any event, the Mōri army attacked during in the morning of 9/15, and, after being surrounded, the Miyagawa forces collapsed in disarray and 750 men were lost. After fleeing, Miyagawa Fusanaga was cornered and either killed in action or took his own life.
Under the more recent theory, the Battle of Oshikibata occurred earlier than 9/15, and may have been on 6/5, but was likely a separate event from the Battle of Akashiguchi.
Based on military chronicles from the Edo period, the battle was understood to have occurred on 9/15 of Tenbun 23 (1554), but, based on academic research, the more prevalent view now is that the battle did not occur on that day. This research concluded that five letters of commendation issued by the Mōri and dated on 9/15 were fabricated or nearly fabricated and lacking in support from authenticated sources.
Furthermore, a letter of commendation dated 6/29 from Harukata to Nakamura Samanosuke, a dogō, or wealthy landowner, from the village of Nukumi in Yamashiro, makes reference to the death in battle of Miyagawa Fusanaga at Akashiguchi. Based on this source, Fusanaga died on 6/5 of Tenbun 23 (1554) at the Battle of Akashiguchi, so it was determined that this battle corresponded to the Battle of Oshikibata. If the Battle of Oshikibata did occur on 6/5, it would also be consistent with the observation by Motonari of the fireflies to ascertain the enemy movements in the summer season. Also, in the description of the conflict displayed at the historic battlefield on the boulder where Miyagawa Kai-no-kami committed seppuku, it refers to the Battle of Oshikibata (Akashi) on 6/5 of Tenbun 23 (1554).
However, based on a letter dated 11/25 of Kōji 3 (1557) to Takamoto, Takakage, and Motoharu in which Motonari made reference to the battle at Oshikibata, the name of the mountain that served as the main base of the Sue army at the time was taken to call the event the Battle of Oshikabata. As a result, the Battle of Akashiguchi and the Battle of Oshikibata which originally referred to the same battle appear to have been affirmed as separate battles on the basis of Edo-period chronicles of the Mōri family.
After the battle, ikki forces from Yamazato in the Saeki District of Aki began to resist and cause problems for the Mōri army. The ikki forces of Yamazato fought tenaciously, continuing their resistance until the fall of their base at the Tomoda-Takamori fortress on 11/25 of 1554.
At the same time, naval battles escalated. In the middle of the sixth month, the Mōri navy launched an attack on Tomidaura (Tomida Inlet) while the Sue naval forces attacked Itsukushima but, owing to defenses at Miyao Castle, failed to make a landing. In the seventh month, the Sue lured naval guard forces from Kure and Nōmi away from the Mōri, but, in the ninth month, guards from the Mōri and Kobayakawa attacked them in the following month.
Motonari subdued elements opposed to the Mōri in Aki, garnering control of almost the entire province. However, after being pinned down in Sanbonmatsu Castle, toward the end fo the eighth month, or on 9/2, Harukata reached a settlement with Masayori and turned his attention to the Mōri. The conflict between the Ōuchi and the Mōri intensified and, before long, in 1555, led to the Battle of Itsukushima.