Lifespan: Tenbun 24, Kōji 1 (1555) to 5/2 of Genna 9 (1623)
Other Names: Zenshirō, Zenbei
Title: Junior Fifth Rank (Lower) and Governor of Iwami, Governor of Iyo
Lord: Matsudaira Nobuyasu → Tokugawa Ieyasu → Tokugawa Hidetada
Father: Matsudaira Masachika
Children: Masatomo, Shigenari, Shigetsugu, Yasunobu, daughter (wife of Hongō Katsuyoshi)
Matsudaira Yasuyasu served as a bushō from the Sengoku to early Edo periods. Yasuyasu was the seventh head of the Ōkusa-Matsudaira family based in the Ōkusa township in the Nukata District of Mikawa Province. The Ōkusa-Matsudaira family was founded by Matsudaira Mitsushige, the fifth son of Matsudaira Nobumitsu of the Iwatsu-Matsudaira. Mitsushige was based at Okazaki Castle. Until 1524, when Okazaki Castle was captured by Matsudaira Kiyoyasu, the Ōkusa-Matsudaira were called the Okazaki-Matsudaira.
In 1555, Yasuyasu was born as the son of Matsudaira Masachika. In 1560, at the Battle of Okehazama, Masachika was killed in clashes at Marune and Washizu fortresses in the prelude to the main battle. In 1563, during the Mikawa Ikkō-ikki, Yasuyasu’s great grandfather, Matsudaira Masahisa, joined with Kira Yoshiaki to rebel against Tokugawa Ieyasu, but, after being defeated, he fled while his landholdings were seized. Consequently, Yasuyasu was forced to revive the Ōkusa-Matsudaira family from scratch.
From an early age, Yasuyasu served Matsudaira Nobuyasu. His first experience in combat occurred in 1572 at the Siege of Futamata Castle at which time he was eighteen years old. Thereafter, he served in numerous battles against the Takeda clan including the Battle of Mikata-ga-hara, the Battle of Nagashino, the Siege of Koyama Castle, the Siege of Suwahara Castle, and the Siege of Takatenjin Castle. Yasuyasu frequently served as the commander of the ashigaru, or lightly armored foot soldiers. In addition to Nobuyasu, Yasuyasu also served under the command of Matsudaira Nobukazu and Ishikawa Kazumasa. After Nobuyasu committed seppuku, Yasuyasu served Tokugawa Ieyasu.
In 1584, at the Battle of Komaki-Nagakute, Yasuyasu, under the command of Mazumasa, defended Komakiyama Castle and then served in the Siege of Kanie Castle. In 1590, during the Conquest of Odawara, he served as a unit commander (samurai general). Thereafter, Yasuyasu served in the Battle of Sekigahara and the Siege of Ōsaka as a unit commander under the command of Tokugawa Ieyasu. On 5/11 of Keichō 6 (1601), he was invested with the titles of Junior Fifth Rank (Lower) and Governor of Iwami.
After the death of Ieyasu, Yasuyasu continued to serve as a unit commander. Tokugawa Hidetada awarded him an increase to his landholdings from 3,000 koku to 6,000 koku. On 10/14 of Genna 8 (1622), he became the standing guard at Sunpu Castle. On 5/2 of Genna 9 (1623), Yasuyasu died at the age of sixty-nine.
Through many battles, Yasuyasu honed his skills as an archer and arquebusier. Early in the Keichō era, when Ieyasu and Hidetada allocated commanders between themselves, Hidetada sought to have Yasuyasu serve under his command, leading to a struggle with Ieyasu. After the death of Ieyasu, Yasuyasu served Hidetada. Thereafter, he joined other former retainers of the Takeda as a member of the otogishū, a group of close associates of the shōgun, and shared battle stories with Hidetada regarding the friends and foes of the Takeda clan.