The Mogami Disturbance was an internal conflict in the Mogami clan of the Yamagata domain of Dewa Province occurring in the early Edo period. The disturbance arose as a result of succession problems following the demise, in 1614, of Mogami Yoshiaki, a daimyō and the eleventh head of the Dewa-Mogami family and first head of the Yamagata domain.
During the latter years of Mogami Yoshiaki, members of the clan maneuvered behind the scenes to position for a successor. Yoshiaki’s eldest son, Mogami Yoshiyasu, would customarily have been the designated successor to the clan, but Yoshiaki did not get along well with Yoshiyasu. Meanwhile, Yoshiaki’s second son, Mogami Iechika, served as an attendant to Tokugawa Ieyasu and Tokugawa Hidetada, establishing close relations with the Tokugawa family. To ensure the survival of the clan in the Edo period, Yoshiaki planned to transfer headship of the clan to Iechika. In 1611, Yoshiyasu was killed by an unknown assailant. This is considered to have been instigated by Yoshiaki, but there is also a theory that this was a solitary act by a retainer, so the cause remains uncertain. There are also several theories concerning the year of the killing. In any event, Yoshiaki later learned that Yoshiyasu intended to seek a reconciliation, so he regretted the loss, and, in the midst of his despair, fell ill. In 1614, he died.
After the death of Yoshiaki, the headship of the Mogami family was inherited by his second son, Iechika. To strengthen his relations with the Edo bakufu, after the start of the Winter Campaign of the Siege of Ōsaka, Iechika arranged for the murder of his younger brother, Shimizu Yoshichika, along with a retainer named Ichikuri Takaharu by Niizeki Hisamasa, the lord of Fujishima Castle, based on suspicions of colluding with those in Ōsaka. During the Winter Campaign and the following Summer Campaign, he served guard at Edo Castle as a demonstration of loyalty to the Tokugawa. In 1617, however, Iechika suddenly died in Edo. While watching traditional drama known as sarugaku, he collapsed, which was suspected of poisoning. After his demise, the headship of the clan was inherited by his only son, Mogami Ienobu. Ienobu was very young (approximately twelve years old) so a plan was made for important decisions to be rendered by the bakufu.
Owing to his youth and inexperience, Ienobu could not exercise effective leadership. Moreover, he was banal and attracted to the literary arts. Dissatisfied with this type of lord, the Mogami band of retainers split between one faction backing Yoshiaki’s fourth son, Yamanobe Yoshitada, in lieu of Ienobu, and another faction continuing to support Ienobu. This led to a fierce internal struggle.
In 1622, Yoshiaki’s nephew named Matsune Akihiro made a claim to Sakai Tadayo, an elder, that Iechika died as a result of poisoning by Tateoka Akinao. Based on this claim, Tadayo investigated Akinao but there was no evidence so Akihiro was turned over to the Tacihbana clan.
Having taken the disturbance seriously, the bakufu sent magistrates including Shimada Toshimasa and Yonekitsu Tadamasa to take control of the Mogami territory and grant Ienobu a fief of 60,000 koku. The bakufu made a decision that, after Ienobu matured, the territory would be returned. Yoshitada and Sakenobe Hidetsuna were not convinced, stating that they could not support Ienobu who relied heavily upon retainers such as Matsune Akihiro.
The attitude of the bakufu stiffened, and, in 1622, the Mogami family was ordered to turn-over the Yamagata domain totaling 570,000 koku. As an exception, Yoshitoshi (previously known as Ienobu) was granted landholdings worth 10,000 koku in Ōmori in Ōmi Province. In this manner, the Mogami family was permitted to continue to exist.
At this time, Honda Masazumi, an elder who served as the representative to receive Yamagata Castle from the Mogami family, was punished while heading toward Yamagata and later removed from his position in connection with an event known as the Suspended Ceiling Incident at Utsunomiya Castle.
The Yamagata domain was granted to Torii Tadamasa, the son of Torii Mototada, but, owing to its great size, the domain was allocated among Tadamasa’s relatives. The Torii clan was later removed from its position, but relatives including the Sakai clan of the Shōnai domain and the Tozawa of the Shinjō domain continued until the Meiji Restoration.
After his death, Yoshitoshi was succeeded by his eldest son, Mogami Yoshitomo, but, owing to Yoshitomo’s youth, the fief was reduced from 10,000 koku to 5,000 koku. Thereafter, his descendants continued as hatamoto, or direct retainers, of the Edo bakufu.
Yamanobe Yoshitada was sent to Ikeda Tadakatsu, the lord of the Bizen-Okayama domain, but, despite having engaged more than ten retainers, retired. In 1633, he was pardoned and, upon orders of the bakufu, sent to serve Tokugawa Yorifusa, the first lord of the Hitachi-Mito domain. Yorifusa engaged Yoshitada as a chief retainer for a fief of 10,000 koku. Later, Yoshitada served as an instructor to Tokugawa Mitsukuni (also known as Mito Kōmon), the second lord of the domain. Thereafter, the Yamanobe family served as chief retainers for generations. At the end of the Edo period, the Mito-Tokugawa family constructed the Sukegawa-Kaibō Castle. The bakufu thereby permitted the residence for purposes of coastal defense. During the construction, Yamanobe Yoshimi, who was serving as the governor and director of coastal defenses, was ordered to become the successor to the clan and to serve as the chief retainer. In exchange for a fief of 10,000 koku, a proclamation was made for a residence in the village of Sukegawa.
Tateoka Akinao was turned-over to the Hosokawa family of the Higo-Kumamoto domain in Kyūshū and his children were engaged to serve the Higo domain, becoming chief retainers. With respect to the Yamanobe family, Yoshitada’s children did not have successors so the clan adopted a child from the Tateoka to inherit the headship of the clan.
The descendants of Matsune Akihiro served as chief retainers of the Date clan in the Iyo-Uwajima domain. At the end of the Edo period, Matsune Zusho served as a deputy to Date Munenari, the eighth head of the Iyo-Uwajima domain. Matsune Tōyōjō, a poet of haiku known as a disciple of a famous author named Natsume Sōseki, was Zusho’s grandson.