Eight Shields of Mogami
The Eight Shields of the Mogami was an alliance of kokujin, or provincial landowners, in the Mogami District of Dewa Province during the Sengoku period. This group is also referred to as the Eight Shields of the Tendō.
The alliance was comprised of branches of the Mogami and Tendō clans, with the most powerful being the Tendō, the Nobesawa, and the Nagatoro clans. Key figures included Tendō Yorizumi, Nobesawa Mitsunobu, Higashine Yorikage, Hosokawa Naomoto, and Kaminoyama Mitsukane. The Mogami clan achieved its period of peak prosperity during the Muromachi period, but branches located across the provinces gradually established independent bases of power while the influence of the Mogami over these clans began to recede.
In 1514, after the death of Date Hisamune, Date Tanemune succeeded him as the fourteenth head of the Date family. Later that year, he defeated Mogami Yoshisada, the Ushū tandai, or Commissioner of Dewa, for the Muromachi bakufu at Hasedō Castle. Tanemune then sent his younger sister to become the wife of Yoshisada in a political marriage and, in effect, placed the Mogami clan under his command. Around this time, the Tendō clan led the formation of an alliance of kokujin from the northern portion of the Murayama District to the Mogami District. This became known as the Eight Shields of the Mogami. The members were nominated as successors after the death of Mogami Yoshisada, allying with the Mogami opposed to the influence of the Date clan. Nevertheless, in 1574, during the Tenshō Mogami Conflict, the alliance joined the side of Mogami Yoshimori and Date Terumune to fight against Mogami Yoshiaki. After the warring parties settled, the alliance also reconciled with Yoshiaki.
In 1577, Yoshiaki attacked the Tendō clan. With the support of the alliance, however, the Tendō defeated the Mogami army and entered into a settlement by which a daughter of the Tendō was tendered as a consort to Yoshiaki. In 1580, Yoshiaki assassinated Kaminoyama Mitsukane, the head of the Kaminoyama clan and a leading member of the alliance. In 1581, he attacked Hosokawa Naomoto, the lord of Oguni Castle, who was a relative of the Tendō clan. In 1582, the daughter received from the Tendō clan died, undermining the stability of the settlement. In 1584, Yoshiaki arranged for the marriage of his daughter, Matsuohime, to Nobesawa Mitsunobu’s son, Matagorō, thereby removing Mitsunobu from the ranks of his opposition
Meanwhile, owing to collusion by those under their command, the Higashine clan was subject to assault and the alliance collapsed. That same year, Yoshiaki launched another attack against the Tendō, toppling Tendō Castle. Tendō Yorizumi fled to Mutsu Province. Thereafter, the clans comprising the alliance submitted to the Mogami clan.
The alliance was comprised of the following families:
Tendō clan – an influential family serving as leaders of the alliance based at Tendō Castle.
Nobesawa clan – based at Nobesawa Castle at Nobesawa Ginzan (silver mine)
Iida clan – based in Murayama
Obanazawa clan – based at Obanazawa Castle
Tateoka clan – based at Tateoka Castle; an illegitimate branch of the Mogami
Nagatoro clan – based at Nagatoro Castle
Rokuta clan – based in the Higashi-Murayama District
Naryū clan – based at Naryū Castle in the environs of Tendō
Other participants in the alliance
Bukkō Temple – an influential temple in Tendō affiliated with the Jōdo sect that had warrior monks
Hosokawa Naomoto – head the Ōshū-Hosokawa clan based at Oguni Castle. The Ōshū-Hosokawa were members of the influential Hosokawa family of the deputy shōgun.
Higashine clan – a branch of the Tendō
Kaminoyama clan (also known as the Dewa-Satomi clan) – based at Kaminoyama Castle. The clan had familial ties to the Mogami but, after Yoshiaki killed Kaminoyama Mitsukane, a member of the clan named Satomi Minbu (who colluded with the Mogami) became the successor and changed the surname to Satomi.