Deployment of the Mōri Clan to Iyo
Date: Eleventh month of Eiroku 10 (1567) to twelfth month of Eiroku 11 (1568)
Location: Iyo Province with a focus of activity at Takashima, the Tosaka Ridge, and Ōzu Castle
Outcome: The Mōri ultimately prevailed in a multi-dimensional conflict that pitted the Mōri and their local surrogates, the Kōno (and by extension the Saionji based on their alliance with the Kōno), and the Murakami, against the Utsunomiya and the Ichijō clan of neighboring Tosa Province.
The Deployment of the Mōri to Iyo occurred from the eleventh month of Eiroku 10 (1567) to the twelfth month of Eiroku 11 (1568). This conflict involved a deployment of the Mōri army from Aki Province in an effort to subjugate Iyo Province in Shikoku.
The expansion of the Mōri clan in western Japan led to inevitable conflict with influential clans to the south of their domain in northern Kyūshū and Shikoku. At this time, the Kōno clan wielded the most influence in Iyo, but did not control the entire province. Clans of various stature such as the Saionji clan of the Uwa District and the Utsunomiya of the Kita District were prevalent, existing in a fluid environment of shifting alliances. During the Eiroku era (1558-70), the Kōno and Saionji clans formed a bond. In opposition to them, Utsunomiya Toyotsuna based at Ōzu Castle allied with Ichijō Kanesada of Tosa Province. In the background of this competition for influence in Shikoku stood other regional powers. The Mōri clan, a sengoku daimyō from Aki Province, had garnered control of Bingo, Suō, Nagato, Iwami, and Izumo provinces in western Japan, while the Ōtomo clan of Bungo province expanded their influence to Buzen, Chikuzen, Chikugo, and Higo provinces in northern Kyūshū.
Kōno Michinobu, the head of the clan, initially wed the daughter of Ōtomo Yoshishige, but, later, he wed the daughter of Shishido Takaie, the son-in-law of Mōri Motonari. This formed a political alliance with the Mōri through marriage. The Kōno also cooperated with the Murakami clan whose naval forces commanded the Seto Inland Sea. The daughter of Shishido Takaie, as an adopted daughter of Kobayakawa Takakage, first wed Murakami Michiyasu, a senior retainer of the Kōno and captain of the Murakami navy, and after the death of Michiyasu, remarried Kōno Michinobu. Around 1563, Michinobu fell ill with paralysis, and during his treatment, Hiraoka Fusazane and Murakami Michiyasu managed clan affairs. Meanwhile, the Ōtomo of Bungo maintained an alliance through marriage with the Ichijō of Tosa. Bungo and Iyo were separated by a strait that was controlled by the Bungo navy, facilitating transport and communications.
The Ichijō of Tosa invade southern Iyo in concert with Utsunomiya Toyotsuna
In 1566, the Ōtomo of Bungo collaborated with the Ichijō of Tosa to attack the Saionji clan in the Uwa District of Iyo. Thereafter, the Ichijō invaded southern Iyo. The following summer, the Utsunomiya of the Kita District began preparation to confront the Kōno, creating tension throughout the district. At the same time, retainers of the Kōno including Hiraoka Fusazane and Murakami Michiyasu deployed in an effort to suppress riots stirred by the Utsunomiya. Around the third month of 1567, Fusazane and Michiyasu attacked several castles held by the Utsunomiya, capturing Kamisugai Castle to the north of Ōzu in four days. Aware that the Utsunomiya were in a precarious situation, Ichijō Kanesada directed his forces northward to reinforce the Utsunomiya. These forces crossed the Mima Plain, arriving near the Uwa Plain. The Kōno forces invaded the Mima Plain and engaged in small-scale skirmishes.
Kōno Michinobu and Murakami Michiyasu appeal for support from the Mōri
On 9/21 of 1567, the Kōno army secured two castles along the route from Tosa Province to the town of Ōzu in southern Iyo. Murakami Michiyasu sent a messenger to the Mōri at Yoshida-Kōriyama Castle in Aki Province to request the Kobayakawa army deploy to Iyo. He made this request after concluding that the situation could not be brought under control with the Kōno army alone. Appreciating the assistance earlier provided by Murakami Michiyasu, Mōri Motonari agreed to offer support under the name of “Appreciation for Itsukushima.” On 10/18, Kobayakawa Takakage acted upon these orders by deciding to dispatch 200 men from Bungo under the command of the Nashiwa clan. During the deployment, however, Michiyasu suddenly fell ill and died after returning to Dōgo on 10/2 (or 10/27) before Motonari’s final decision to send soldiers in support of the campaign.
Owing to the death of Michiyasu, the deployment of the Mōri to Iyo hung in the balance, but Takakage did not yield, viewing it as his own battle, and decided to deploy. Meanwhile, Nomi Munekatsu, who had a more intimate understanding of the situation in Iyo, prepared to fight against the Ōtomo in Kyūshū, and could not quickly return. In a letter dated 11/3 from Takakage to Munekatsu, Takakage declared that the Ichijō clan could not be defeated without reinforcements. Takakage maintained close communication with the family of Murakami Michiyasu and Murakami Yoshitsugu, and consultations led in the direction of military action. With Yoshitsugu serving as the guide, the Kobayakawa deployed in the winter to Iyo.
The Battle of Takashima and the Battle of Tosaka Ridge
In the first month of 1568, the Ichijō pulled along members of the Mima and Moroyama families along the border of Iyo and Tosa to apply pressure upon and subjugate the Saionji clan. Adding these forces, the Ichijō army proceeded to Takashima to the east of the Tosaka Ridge in Iyo. The Kōno forces attacked the Ichijō base at Takashima, but were repelled. Upon orders from Kobayakawa Takakage, the Kaminoseki navy from Suō Province and the Murakami navy from Innoshima commenced operations toward Iyo. Further, Nomi Munekatsu, who was most knowledgeable about the situation in Iyo, coverged with Takakage and planned for a showdown against the Ichijō army.
In the midst of confronting the Ichijō, the Kōno lost Murakami Michiyasu, so Murakami Yoshitsugu took over the main force to establish a fortress on Tosaka Ridge. With their passage blocked, the Ichijō attacked the fortress on 2/4, unleashing a fierce battle. Although the fortress nearly fell, reinforcements led by Yoshitsugu resulted in a major defeat for the Ichijō army. Nevertheless, the clash did not result in a decisive victory, and the armies continued in a stand-off between Takashima and Tosaka Ridge.
The landing of Kobayakawa Takakage in Iyo
In the middle of the second month, Mōri Motonari and Kobayakawa Takakage examined the situation and decided that Takakage would go to Iyo. This caused a hurried atmosphere at Takakage’s base at Shintakayama Castle. Although Takakage planned to set sail on 3/1, the arrival of Shishido Takaie and Fukubara Sadatoshi from Yoshida-Kōriyama was delayed so the Mōri army set sail for Iyo between the middle and end of the third month. Takakage landed ahead of them, while Ichijō Kanesada led kokujin from Tosa toward Takashima to support the Utsunomiya who were under attack at Ōzu and Hachimanyama castles. The Kobayakawa army strengthened defenses near the fortress at Tosaka Ridge, blocking the advance of the Ichijō army. To ascertain the movements of the Utsunomiya and Ichijō forces, Takakage extended his stay at Tosaka Ridge.
As the Mōri forces poured into Iyo, the stalemate suddenly began to change. The Mōri army proceeded to the environs of the base of the Utsunomiya in Ōzu, resulting in a clash against the allied forces of the Utsunomiya and Ichijō. Despite valiant efforts, the defenders incurred a bitter defeat, while the Mōri proceeded to steadily gain control of the surrounding area. Ōzu Castle likely fell to the Mōri at this time.
The subjugation of Iyo by Murakami Yoshitsugu and Nomi Munekatsu
Around the fourth month of 1568, the Ōtomo commenced operations in northern Kyūshū. Takakage and Munekatsu scrambled to respond. Without having achieved a decisive outcome between the Mōri’s main force and the Ichijō, Takakage delegated the command to Ura Motonobu, the younger brother of Munekatsu, and returned to Aki. Just two months later, Takakage went to northern Kyūshū to engage the Ōtomo forces. The Ichijō continued their stand-off with the Mōri in Iyo. Utsunomiya Toyotsuna holed up in Ōzu Castle, opposite the Kōno. Murakami Yoshitsugu then captured Shimosugai Castle and the balance gradually tipped in favor of the Mōri and their local surrogates, the Kōno. Chōsokabe Motochika, who had submitted to the Ichijō, sent a congratulatory letter to Murakami Yoshitsugu.
In the eleventh month, Nomi Munekatsu gathered his forces and deployed a second time to Iyo in a bid to conquer the Utsunomiya. Toyotsuna surrendered and turned over Ōzu Castle, becoming a prisoner of the Mōri.
Consequences of the deployment to Iyo
The deployment of the Mōri forces to Iyo added another component to the struggle between the Ichijō clan of Tosa and the Kōno of Iyo. In the background, the Mōri opposed the Ōtomo in Kyūshū. Knowing that the Mōri aimed to invade northern Kyūshū, the Ōtomo benefited by having them pinned down to a degree in Iyo as a means to delay their invasion. The Mōri unavoidably confronted battles in Kyūshū and Shikoku. From the perspective of the Kobayakawa clan, this offered an opportune moment to expand their influence in Shikoku, and the control of the seafaring pirates by the Murakami navy was a significant result. The situation did not allow for the Kōno to independently govern Iyo, so the clan submitted to the Mōri and Kobayakawa, and through their support managed to control only their own domain. Kōno Michinobu wed the widow of Murakami Michiyasu (the daughter of Shishido Takaie) named Tenyū Eiju and died of illness in 1570. The orphan of Murakami Michiyasu became his successor and may have been Murakami Michinao.
Thereafter, the Mōri and Ōtomo contested for control of northern Kyūshū, marked by violent clashes at the Battle of Tachibanayama, the Battle of Moji Castle, and the Battle of Tatarahama. These conflicts continued until the time of death of Mōri Motonari.
The deployment of the Mōri army to Iyo resulted in major losses and a decline in influence for the Ichijō clan of Tosa. Chōsokabe Motochika, who had been under their governance, began to operate independently, showing signs of autonomy. This outcome was a factor in Motochika’s expansion of power in Shikoku.