Masayuki was the 3rd son of Sanda Yukitaka (1512-1574) and like his father first served Takeda Shingen. His first taste of battle, in fact, is said to have been at the famous 4th Battle of Kawanakajima. He became head of the Sanada after his two elder brothers, Nobutsuna and Masateru, were killed at Nagashino in 1575. As the power of the Takeda declined, Masayuki expanded into Kôzuke and took Numata from the Hôjô in 1580. In 1585 Tokugawa Ieyasu demanded that Numata be returned to the Hôjô as part of a Tokugawa-Hôjô agreement signed that year. Masayuki refused and defeated a Tokugawa army sent to chastise him near Ueda after recieving the assistance of Uesugi Kagekatsu. Masayuki made peace with the Tokugawa by sending his son Nobuyuki as a hostage to Hamamatsu, and secured cemented an alliance with the Uesugi by sending his son Yukimura as hostage to Echigo. That same year, the Hôjô had tried and failed to bring down Numata, which was held by Masayuki's uncle, Yasawa Yoritsuna.

Masayuki joined in Toyotomi Hideyoshi's 1590 Odawara Campaign by attacking Hôjô forts in Kozuke and saw his territories increased somewhat as a result. In 1600 he initially acted as if in support of Tokugawa, then declared for the 'western' cause, although only after ordering his son Nobuyuki to join the Tokugawa camp. He and his son Yukimura (who was known at the time as Nobushige) were besieged in Ueda by Tokugawa Hidetada but succesfully resisted the Eastern forces, doing so in such a staunch manner that Ueda is considered one of the 'classic' sieges of Japanese history. After the Sekigahara campaign was concluded, Tokugawa Ieyasu banished both Masayuki and Yukimura to Kûdoyama, where the former died some years later. Yukimura would go on fight and die for the Toyotomi cause at Osaka Castle (1614,1615), while Nobuyuki would live into his 90's, the elder branch of the Sanada thus preserved.

Masayuki is considered one of the most skilled samurai commanders of the later Sengoku Period, and foul play has traditionally been suspected in his death.

See also: The 16th Century Sanada Genealogy

By FwSeal