菊池氏
The Saigō family was one branch of the distinguished Kikuchi clan of Kyushu that had migrated northward to Mikawa Province in the fifteenth century. In 1524, the forces of Matsudaira Kiyoyasu (1511–1536), the grandfather of Tokugawa Ieyasu, stormed and took the Saigō clan's headquarters at Yamanaka Castle during his conquest of the Mikawa region. Shortly after the battle, Saigō Nobusada, the third head of the Saigō, submitted to the Matsudaira clan. Following the untimely death of Kiyoyasu in 1536, and the ineffectual leadership and early death of Matsudaira Hirotada (1526–1549), the leaderless Matsudaira clan finally submitted to Imagawa Yoshimoto (1519–1560) of Suruga Province, east of Mikawa. When the Matsudaira fell to the Imagawa, the clans of their retainers, which included the Saigō, likewise submitted to the Imagawa. Following the Battle of Okehazama (1560), Saigō Masakatsu attempted to re-assert the independence of the clan while yielding some land concessions to the Imagawa. In response, Imagawa Ujizane arrested thirteen Saigō men, and had them vertically impaled near Yoshida Castle. The executions did not deter the Saigō, and in 1562 the Imagawa launched punitive invasions of east Mikawa and attacked the two main Saigō castles. Masakatsu was killed in the battle of Gohonmatsu Castle; his eldest son Motomasa was killed during the battle for Wachigaya Castle. Clan leadership passed to Masakatsu's son, Saigō Kiyokazu (1533–1594), who pledged his loyalty to the Matsudaira clan, under the leadership of Tokugawa Ieyasu, in their mutual struggle against the Imagawa. In 1569, the power of the Imagawa ended with the siege of Kakegawa Castle.