Lifespan: Tenshō 11 (1583) to 5/14 of Keichō 17 (1612)
Title: Junior Fourth Rank (Lower), Governor of Hida, Chamberlain
Clan: Gamō (Hashiba)
Lord: Toyotomi Hideyoshi → Toyotomi Hidetaka → Tokugawa Ieyasu → Tokugawa Hidetada
Father: Gamō Yasuhide (Ujisato)
Mother: Sō-ō-in (second daughter of Oda Nobunaga)
Wife: [Formal] Furihime (third daughter of Tokugawa Ieyasu)
Children: Tadasato, Tadatomo, Sūhōin (formal wife of Katō Tadahiro)
Gamō Hideyuki served as a bushō and daimyō during the Azuchi-Momoyama and early Edo periods. Hideyuki served as the head of the Mutsu-Aizu domain.
In 1583, Hideyuki was born the son of Gamō Yasuhide (who several years later changed his name to Ujisato). Hideyuki was either the first or second son. He was frail of health from birth, and Ujisato had his other son named Tsuruchiyo serve as a monk at the Nanzen Temple in Kyōto. Ujisato determined that if this son was able to handle the responsibility of a bushō then he would become Ujisato’s successor, and, if not, then he would have him continue to serve as a monk.
After Ujisato suddenly died on 2/7 of Bunroku 4 (1595), Hideyuki inherited the headship of the clan. At this time, he was given the Hashiba surname. An inheritance issue arose as a result of under-reporting of the total value (koku) of the fief. There are two theories regarding the outcome. First, the verdict rendered by Toyotomi Hideyoshi in his role as the taikō, or regent, was to appropriate the territory in Aizu for the administration and to grant a fief of 20,000 koku in Ōmi Province. Under this theory, the inheritance was recognized at the same time territory was garnished. Second, after recognizing the inheritance, improprieties by elder retainers were discovered, so the territory was seized and a fief of 20,000 koku in Ōmi was granted as a type of pardon. Tokugawa Ieyasu was the father-in-law of Tsuruchiyo so, from the perspective of Hideyoshi, Ieyasu had a reason to investigate the issues. Thereafter, Hideyuki may have inherited a fief of 920,000 koku in Aizu based on an approval by Toyotomi Hidetsugu (the kanpaku, or Chief Councillor of the Emperor), and, furthermore, upon orders of Hideyoshi, the inheritance was subject to the condition that Hideyuki receive Furihime (the third daughter of Ieyasu) as his formal wife. Under these conditions, in the fifth month of 1595, Asano Nagamasa dispatched a messenger and, upon orders of Hideyoshi, castles other than Aizu-Wakamatsu Castle, along with seven secondary castles (Yonezawa, Shirakawa, Tamura (Moriyama), Nihonmatsu, Shiroishi, Tsugawa, and Yanagawa), were to be destroyed. Tokugawa Ieyasu then assigned Narita Ujinaga and Ōtawara Harukiyo to oversee the destruction work.
Given his youth, Hideyuki did not possess the experience of his father, Ujisato, and therefore was unable to properly lead the family. This ultimately led to internal conflicts among the senior retainers in an event known as the Gamō Disturbance. To offset the influence of Ieyasu given the family ties with Hideyuki, Hideyoshi may have sought to demote the family, having Ishida Mitsunari manipulate events from behind the scenes in an effort to undermine Hideyuki. Therefore, the youth and inexperience of Hideyuki were not necessarily the only reasons for the transfer and demotion of the Gamō family.
Transfer to Utsunomiya and the Battle of Sekigahara
In the third month of 1598, Toyotomi Hideyoshi ordered the Gamō family under Hideyuki to transfer from Aizu in Mutsu Province to Utsunomiya in Shimotsuke Province, incurring a reduction in their fief from 920,000 koku to 180,000 koku. The inability of the clan to resolve internal conflicts giving rise to the Gamō Disturbance was an ostensible reason for the demotion. Other theories include the possibility that Hideyoshi was interested in having Ujisato’s wife as a consort, but was unhappy to learn that she committed to the life of a nun, or that differences with Ishida Mitsunari were used as a pretext for demotion because Hideyuki was married to the daughter of Tokugawa Ieyasu.
Hideyuki built a residence for a military family, drawing a clear distinction from the residences of the townspeople. He also built an entrance below the castle with a checkpoint and promoted the development of the area below the residence. He allowed merchants who came from the traditional home of the Gamō clan in Hino in Ōmi Province to come under his protection and reside along the Kama River running to the north of the castle, fostering commercial activity under the name of the town of Hino.
In 1600, after the Battle of Sekigahara, Tokugawa Ieyasu and his third son and designated successor, Tokugawa Hidetada, led their armies toward the west so Hideyuki remained at his base in Utsunomiya to keep the army of Uesugi Kagekatsu in check as well as maintain security around his castle. Toyotomi Hideyoshi had earlier assigned the former territory of the Gamō in Aizu to Kagekatsu.
Return to Aizu and early demise
After the Battle of Sekigahara, Hideyuki was rewarded for his contributions to the Eastern Army with a fief of 600,000 koku in territory in Mutsu seized from the Uesugi clan so he returned to Aizu. Owing to his marriage to Furihime, after the establishment of the Edo bakufu, Hideyuki was relied upon heavily as a member of the Tokugawa family. In 1607, he was given the honorary surname of Matsudaira.
However, the powerful Aizu Earthquake in the autumn of 1611, as well as a resurgence of internal conflict, may have caused anxiety that contributed to the sudden demise of Hideyuki on 5/14 of Keichō 17 (1612) at the age of thirty. Hideyuki was succeeded by his eldest son, Gamō Tadasato, at the age of ten. His widow, Furihime (the third daughter of Tokugawa Ieyasu), served as his guardian. She then came into a severe conflict with Oka Shigemasa, the chief retainer, over matters of governance of the domain. Moreover, this reignited the internal conflicts that erupted after the death of Ujisato so her father (Ieyasu) and older brother (Tokugawa Hidetada) were concerned about disruption in the clan, taking steps including dispatching a censor to go over the laws. This state of affairs culminated in Ieyasu summoning Shigemasa to Sunpu Castle and ordering him to commit seppuku the following year.