Lifespan: Eishō 5 (1508) to 3/27 of Tenshō 7 (1579)
Title: Governor of Shimotsuke, Master of Imperial Guards of the Left Division
Lord: Rokkaku Sadayori → Rokkaku Yoshikata → Rokkaku Yoshiharu → Oda Nobunaga
Father: Gamō Takasato
Siblings: Sadahide, Takakiyo, Katahiro, Hidehiro, Aoki 梵純, sister (wife of Gamō Hidenori)
Wife: Daughter of Mabuchi Yamashiro-no-kami
Children: Katahide, Aochi Shigetsuna, Ogura Sanetaka, daughter (formal wife of Seki Morinobu), daughter (wife of Kanbe Tomomori)
Gamō Sadahide served as a bushō during the Sengoku and Azuchi-Momoyama periods. He was a retainer of the Rokkaku and Oda clans. Sadahide served as the lord of Hino Castle in the Gamō District in the south-central portion of Ōmi Province.
In 1508, Sadahide was born as the son of Gamō Takasato. Together with his father, Sadahide served as retainers of the Rokkaku clan who were the sengoku daimyō of southern Ōmi Province. Takasato was from a cadet family of the Gamō clan. Sadahide’s cousin, Gamō Hidenori, inherited the headship of the main branch of the Gamō. Hidenori was aligned with the Ashikaga bakufu, while Takasato and Sadahide garnered the trust of their lord, Rokkaku Sadayori. With the backing of Sadayori, Sadahide received one of the characters in his name from his lord. Sadahide received his formal wife from the Mabuchi clan, one of the leading retainers of the Rokkaku family, thereby solidifying his status among the Rokkaku.
In 1522, Sadahide attacked Gamō Hidenori at Otowa Castle. In the third month of 1523, after a siege lasting for eight months, he compelled the surrender of Hidenori. Through the mediation of Rokakku Sadayori, a settlement was reached whereby Hidenori transferred the headship of the Gamō family to Sadahide. Sadahide then inherited the family. Otowa Castle, which had at that time served as the base of the Gamō clan, was destroyed by Sadayori. In 1525, Hidenori was murdered in Kaigake Castle. Thereafter, during the first half of the Tenbun era (1532 to 1555), Sadahide built Hino Castle where he established his base.
As a retainer of Sadayori, in 1530, Sadahide deployed to Kyōto and, in 1531, joined the fight against Azai Sukemasa at the Battle of Minoura, garnering twenty-nine heads. Sadahide participated in a majority of Sadayori’s major engagements, making significant contributions. In 1539, Sadahide went to Kyōto on behalf of Sadayori. In 1549, he fought against Miyoshi Nagayoshi in Settsu Province. In 1552, after the death of Sadayori, Sadehide served Sadayori’s son, Rokkaku Yoshikata, and was given authority to invade Ise Province.
In 1558, he entered the priesthood. In 1559, he attacked Sawayama Castle which was associated with Azai Hisamasa, and, in 1562, he further attacked Yabutsude Castle in Ōmi defended by Tanamura Mikawa-no-kami. Later that year, he went to the capital for Yoshikata.
Sadahide sent his second son, Shigetsuna, to the Aochi clan affiliated with the Sasaki family, and his third son, Sanetaka, to be adopted by the Ogura clan who had been predecessors of the attack on Ise. He arranged for his daughters to be wed to Seki Morinobu and Kanbe Tomomori of Ise, forging an independent base of power through political marriages.
Sadahide also excelled in local governance, and, with the support of Sadayori, conducted planning for the town below the castle as well as commercial policies. He enabled the production of lacquerware along with establishing the town of Hino in the Gamō District. He also soon realized the importance of arquebuses and solicited arms manufacturers to the town.
In 1563, during an internal conflict in the Rokkaku clan known as the Kannonji Disturbance, Sadahide harbored Gotō Takaharu as well as his lord, Rokkaku Yoshiharu, and worked toward a settlement of the situation. In 1564, Ogura Sanetaka (Sadahide’s third son who he had sent for adoption to the main branch of the Ogura clan) was killed in a dispute with the Ogura-nishi family (one of the branches of the Ogura clan). Sadahide sought to avenge the killing with attacks on the bases of the Ogura-nishi family at Yamakami and Yao castles, decimating the Okgura-nishi family and expanding his own territory. In 1567, he signed in his capacity as a clan elder a set of provincial laws prepared by the Rokkaku clan. In 1568, after the elimination of the Rokkaku clan, Sadahide then served under Oda Nobunaga.
Sadahide died in 1579 at the age of seventy-two.
Of the senior retainers of the Rokkaku family, Sadahide was a leader among leaders. In 1562, he personally issued proclamations known as tokuseirei to creditors such as financiers and money-brokers requiring them to forgive the debts of their borrowers.
Sadahide was connected to Rokkaku Sadayori through a subservient relationship, but, from the era of Sadayori’s son, Yoshikata, the relationship reversed whereby Sadahide wielded more power than Yoshikata. In 1564, in the Kannonji Disturbance, Yoshikata was ousted from his base and endured hard times so Sadehide loaned him money upon a firm promise that it be repaid.