Siege of Kōzuki Castle

The Siege of Kōzuki Castle (上月城の戦い, Kōzuki-jō no Tatakai) occurred in 1578, when the army of Mōri Terumoto attacked and captured the castle of Kōzuki in Harima Province. Kōzuki had been taken by Toyotomi Hideyoshi the previous year and entrusted to Amago Katsuhisa. When it fell to the Mōri, Amago committed hara-kiri. Amago's loyal and heroic general Yamanaka Yukimori was captured and killed in the battle.

It is popularly believed in Japan that Yamanaka Shikanosuke, Amago's general, "sold" Amago's life, for the safety of his own men.

The Oda forces were so vastly outnumbered and surrounded in the castle that victory was impossible. Yamanaka Shikanosuke sent a message to the Mōri general offering to surrender, and offering the ritual suicide of his master (Amago). The offer was accepted, Amago committed suicide, and his forces surrendered.

What precisely happened to Yamanaka Shikanosuke after the battle is unclear. Though some sources say he died in the battle, others state that he became a vassal of the enemy lord, Mōri Terumoto, but was assassinated on Mōri's order (along with his new wife).

Amago Katsuhisa, the Oda vassal lord of Kōzuki Castle, though a member of the samurai class, was not especially experienced or trained as a warrior. Oda Nobunaga was running out of qualified battle-hardened lords to hold his territories, so Katsuhisa was called to Kōzuki from Kyoto, where he was studying to be a Buddhist monk. Katsuhisa was very young, in his early twenties, when he died. A memorial stone stands with his name engraved, along with Buddhist inscriptions, where he took his own life.