Satomi Yoshihiro

Satomi Yoshihiro (1530-1578) was head of the Satomi clan, a Sengoku daimyo house based in Awa Province, and is remembered for bringing the clan to its greatest territorial extent on the Bōsō Peninsula.

Succession

His father was Satomi Yoshitaka. From the early Eiroku era his father began transferring real authority to him, and he changed his name from Yoshishun to Yoshihiro accordingly. When Yoshitaka took the tonsure and entered the priesthood in 1562, Yoshihiro formally succeeded as head of the clan.

The Second Battle of Kōnodai

In 1564 Yoshihiro clashed with the Late Hōjō at Kōnodai in Shimōsa Province. In this second battle at that site he was heavily defeated by Hōjō forces under commanders including Hōjō Tsunanari, and was forced to withdraw to Awa. With most of Kazusa Province lost to surrounding powers, the Satomi clan faced a crisis of survival.

Mimuneyama and the Clan's Zenith

The reversal came at the Battle of Mimuneyama in 1567, where Yoshihiro broke the Hōjō forces and restored the clan's fortunes. He subsequently established Sanuki Castle as his base and consolidated domain rule spanning Awa, Kazusa, and Shimōsa — the largest territory in Satomi history and the height of the clan's power as a Bōsō daimyo house.

Conflict and Peace with the Hōjō

Yoshihiro initially pursued a diplomatic line of allying with Uesugi Kenshin of Echigo and Takeda Shingen of Kai against the Late Hōjō, and in 1561 joined Kenshin's siege of Odawara Castle. As Kenshin and Shingen each turned their attention to other fronts, however, the Satomi lost the support of those alliances. In 1577 Yoshihiro reversed his hostile stance and concluded peace with the Late Hōjō.

Death and the Division of the Clan

In 1578, shortly after the death of Uesugi Kenshin, Yoshihiro too died suddenly at Kururi Castle. His deathbed instruction to divide the domain between his younger brother and his eldest son became a cause of the internal fragmentation that followed. The death of the lord who had dominated the Bōsō Peninsula marked the turning point of Satomi power.