Nighttime Attack at Mitsuhama
Date: 9/18 of Keichō 5 (1600)
Location: In Mitsu on the shore of Matsuyama, with ancillary clashes on the Hatadera Plain and Mount Dōgo
Outcome: The Katō deceived the Mōri and then launched a surprise attack at nighttime that resulted in a significant loss for the Mōri, followed by clashes with retainers of the Kōno on Mount Dōgo. The remnants of the Mōri returned to Aki Province.
The Nighttime Attack at Mitsuhama occurred on 9/18 of Keichō 5 (1600) in the environs of Mitsuhama in Iyo Province. The clash involved Katō forces of the Eastern Army against an alliance of the Mōri clan and former retainers of the Kōno clan. This event was connected to the Battle of Sekigahara, and, among other names, is also referred to as the Iyo Sekigahara.
To capitalize on the chaos associated with the Battle of Sekigahara, the Mōri clan devised plans to divide the territory in Iyo Province, scheming from around the eighth month against Katō Yoshiakira, Tōdō Takatora and other kokujin, or provincial landowners, of the Eastern Army based in Iyo. In particular, the Mōri had their sights set on the territory ruled by Yoshiakira, dispatching an army from Takehara in Aki Province to invade Iyo. The Kōno clan sought to restore their influence in Iyo, so the Mōri positioned themselves as a successor to the Kōno, appointing Kōno Michinori as the commanding general of the invading forces. The army was comprised of 3,500 mounted soldiers and several hundred vessels. The invading forces included retainers of the Mōri such as Katsura Mototsuna and Shishido Kageyoshi, along with Sone Kagefusa, a kokujin from Uchiko in Iyo, and naval officers including Murakami Yoshitada of the Innoshima Navy and Murakami Motoyoshi of the Noshima Navy in the Seto Inland Sea. In addition, former retainers of the Kōno launched uprisings in the province.
On 9/10, the Mōri attacked a retainer of the Katō named Ishikawa Takatsugu defending Kurushima Castle, but the castle was difficult to assault so the forces directed their attention toward Masaki Castle instead.
On 9/17, the Mōri landed on a beach called Mitsuhama in Matsuyama after passing by an island known as Gogoshima. The forces converged with Hiraoka Naofusa, a retainer of the Kōno and lord of Ebara Castle in Matsuyama. The men set-up a camp at Furumitsu approximately eight kilometers from Masaki Castle, scattered among local residences. The unit led by retainers of the Kōno moved to Ebara Castle.
After their arrival, the Mōri promptly dispatched Sone Takafusa as a messenger to Masaki Castle, demanding that the defenders turn over the castle in accordance with a written order bearing the seal of Toyotomi Hideyori. In addition, Murakami Takeyoshi, Murakami Motoyoshi, Shishido Kageyoshi and others jointly signed a letter dated 9/15 addressed to Takei Motoi, a wealthy merchant from Masaki threatening that if he aligned with the Katō, his wife and children would all be killed, so he must cooperate with them.
In response to the demands, the commanders for the Katō, Katō Tadaakira (the younger brother of Yoshiakira), Adachi Shigenobu, and Tsukuda Kazunari devised a plan feigning that Kazunari was ill so they could not meet directly with Sone Kagefusa, but would vacate the castle provided the women and children have time to leave. The defenders then gave food and drink to local peasants, while the forces defending the castle misinformed the Mōri in Mitsu that Kazunari was ill, as though they welcomed an attack by the Mōri.
Moreover, the defenders refused an offer from Tōdō Takatora, lord of Uwajima Castle, to send reinforcements.
From midnight, Kazunari led a unit of Katō retainers fewer in number than the Mōri, setting fires around the forces while launching an attack. After fierce fighting until morning at Kariya-hatake and Furumitsu the Mōri were defeated. The Mōri suffered significant casualties. Murakami Motoyoshi and Sone Kagefusa were killed, while Shishido Kageyo was wounded. On 9/19, Tsuzukidani Magoemon arrived, gathered the irregular forces, and, along with soldiers from Ebara Castle, robbed the defeated army of their possessions. He then encountered the Katō forces on the Hatadera Plain, and, together with Hiraoka Naofusa, sheltered in the Nyorai Temple in Kume. Meanwhile, Kōno Michinori sought refuge in Ebara Castle.
When the Katō forces attacked the Nyorai Temple, Naofusa retreated with the irregulars associated with the Kōno to Mount Dōgo, wounding Tsukuda Kazunari and shooting and killing Kuroda Kyūbei, the commanding officer of the Katō, with an arquebus. Later, Yoshiakira opined that although Kyūbei was brave, he did not act strategically.
Despite his injuries, Kazunari assembled his forces at Mount Dōgo to continue the fight. On the evening of 9/22, a spy then informed him that the Mōri forces led by Tsuzukidani Magoemon in Ebara were headed the next day toward Mitsu to return to Aki Province. At the break of dawn on 9/23, the Katō forces clashed with the retainers of the Kōno in the environs of Mount Dōgo and with the Mōri on Mount Mitsunoki. The Mōri fled north, but the Katō did not have leeway to pursue them. That evening, news arrived that the Western Army had been defeated at Sekigahara. The next day, the Mōri retreated from the Kazahaya shore. After the withdrawal, Kōno Michinori served as a retainer of the Mōri and later died in Yamaguchi.
Kainō Michimori (lord of Ōkuma Castle), along with Minami Michitomo and Masaoka Shigeuji who served as priests at the Kōno Shrine, rebelled in concert with the battle, although details are uncertain.
The clashes caused the main building of the Itsukushima Shrine in Mitsu to be burned.
The Mōri did not directly invade the territory of Tōdō Takatora, but took steps to incite rebellion by former retainers of the Saionji clan including the Kushi and Yamada clans. As a result, Misse Rokubei from the village of Matsuba in the Uwa District colluded with the Mōri and started an uprising. In the course of suppressing them, the commander of the ashigaru, or foot soldiers, named Rikiishi Jihei was killed in action. After pulling back once to Uwajima, the uprising was finally put down through the efforts of Kurita Kunai, a former retainer of the Utsunomiya clan.
Based on a letter associated with the Mōri family, preparations for the invasion of Iyo were led primarily by Sase Motoyoshi, Murakami Takeyoshi (father and son), and Sone Kagefusa. There is no reference to Shishido Kageyo or Kōno Michiyori served as lead commanders.
Named bushō under the command of Murakami Takeyoshi who deployed from the Shiwaku Islands in the Seto Inland Sea included Miyamoto Sado-no-kami Soyo, Yoshida Bungo-no-kami Fukumasa, Miyamoto Sado-no-kami Fukuori, Miyamoto Sado-no-kami Fukusato, and Yoshida Matazaemon Tadatoshi. For the Battle of Sekigahara, the Shiwaku Islands were held by the Eastern Army, and the leaders were divided into two units. However, for the attack on Mitsuhama, it is not known which bushō finally participated.
There is a legend that a natural son of Otsuya-no-kata (an aunt of Oda Nobunaga) named Baba Rokudayū fought on behalf of the Murakami navy and died at this battle.