Lifespan: Tenbun 9 (1540) to 8/28 of Keichō 15 (1610)
Rank: bushō; daimyō
Title: Chief of the Right Division of Outer Palace Guards
Father: Amago Haruhisa
Mother: Daughter of Amago Kunihisa
Siblings: Chitose, (Matashirō?, Yōsetsu), Yoshihisa, Toyohisa, Hidehisa
Wife: [Formal] Daughter of the Kyōgoku clan
Children: Tomohisa (illegitimate child while a guest of the Mōri clan), Amago Motosato (adopted)
Amago Yoshihisa, a daimyō, was a member of the Amago clan in Izumo Province. He was the second son of Amago Haruhisa, sengoku daimyō of Izumo. Yoshihisa received the first character in his name from Ashikaga Yoshiteru, the thirteenth shōgun of the Muromachi bakufu.
In 1560, Yoshihisa became the lord of the clan following Haruhisa’s sudden death. This occurred in the midst of an ongoing conflict between the Amago and the Mōri for control of the Iwami-Ginzan silver mine. The turmoil caused retainers of the Amago to hold a secret funeral service for Haruhisa in Gassantoda Castle. Moreover, Haruhisa’s purge in 1554 of the shingūtō, a powerful band of elite warriors, had eliminated capable family members and stirred frustration among the kokujinshū, or provincial landowners.
Thereafter, the Mōri inferred that Haruhisa had suddenly died, and launched another assault on Iwami Province. Rather than continue to draw the battles lines with the Mōri over control of the Iwami-Ginzan silver mine, Yoshihisa proposed a settlement mediated by the Muromachi bakufu. Viewing the offer as an opportunity to plan further attacks against the Amago, Mōri Motonari requested non-intervention in Iwami Province as a condition for peace. Yoshihisa’s acceptance of this condition served to isolate the Fukuya clan who had relied on the Amago in a rebellion against the Mōri, in addition to reinforcements stationed in Iwami to support the Fukuya. This included retainers of the Amago such as Honjō Tsunemitsu, Ushio Hisakiyo, and Tako Tokitaka, along with kokujin allied to the Amago such as Onsen Hidenaga. Yoshihisa’s concession ultimately contributed to the fall of the Amago forces. Meanwhile, Yoshihisa entered into an alliance with Ōtomo Yoshishige, the leading daimyō from Kyūshū, encouraging the Ōtomo to invade Suō Province to pressure the Mōri on two fronts.
In 1562, Honjō Tsunemitsu betrayed the Amago in favor of the Mōri, while Ushio Hisakiyo and Onsen Hidenaga retreated to Izumo. The Mōri captured Sakka-Iwayama Castle on the border of Iwami and Izumo, leading its lord, Tako Tokitaka, to kill himself. Under threat of imminent attack, powerful kokujin from western Izumo, including the Akana and Mizawa clans, switched their allegiance to the Mōri. Mōri Motonari seized this as an opportunity to launch an invasion of Izumo. In 1563, Shiraga Castle defended by the Matsuda clan fell to the Mōri forces, followed by Kumano Castle without resistance. Clans including the Akana, the Mizawa, and the Mitoya, stationed in ten auxiliary castles known as the Amago jikki, or the ten flags of the Amago, intended to protect Gassantoda Castle, yielded to the Mōri with minimal resistance. Only a portion of the kunishū in Izumo dug-in to fight, evidencing the limits of Haruhisa’s influence and lack of central authority. The situation further reflected the internal discord and dissatisfaction within the Amago clan.
In 1564, the loss of Ebi Castle in Hōki Province impeded supply routes for the Amago clan. This made it difficult to communicate with allied clans such as the Maki and Gotō, retainers of the Emi and Miura clans of Mimasaka Province. Gassantoda Castle became isolated. In 1565, the Mōri laid siege to the castle in the Second Siege of Gassantoda Castle. The Mōri army attacked Toda Castle, but were met with stiff resistance from spirited defenders and incurred mounting casualties. This caused them to shift tactics by halting the attacks and instead waiting until the supplies of the defenders ran out. As the provisions in Toda Castle began to dwindle, the morale of those inside declined. Clans that had served as retainers of the Amago for generations, including the Kamei, the Kōmoto, the Sase, the Tō, and the Ushio surrendered to the Mōri. In 1566, Uyama Hisakane, a retainer of the Amago, was executed on suspicion of plotting to rebel against Yoshihisa, marking a further deterioration of the atmosphere inside the castle.
Toward the end of 1566, Yoshihisa decided to turn over the castle, notifying Motonari of his intent to surrender. Motonari replied with a message sealed in blood that a settlement could be reached if Yoshihisa accepted a family status after Kikkawa Motoharu (Motonari’s second son) and Kobayakawa Takakage (Motonari’s third son). Yoshihisa accepted these terms and opened the castle. Following the loss of Gassantoda, the defenders of the remaining Amago jikki outlying castles surrendered one after another to the Mōri. Motonari spared the lives of Yoshihisa and his younger brother, confining them to Enmyō Temple in Aki Province. This marked the end of the Amago clan as a daimyō family.
Decades later, in 1589, Yoshihisa was treated by Mōri Terumoto as a guest of the Mōri, and furnished a residence in Shiji in Aki Province. In 1596, Yoshihisa entered the Gokokuzen Temple in the Abu District of Nagato Province, became a monk, and assumed the name of Yūrin. He died in 1610, and, upon request of the Mōri, his nephew, Amago Motosato, became the seventh head of the Amago clan.