Matsudaira Nobuyasu

Who They Were

Matsudaira Nobuyasu (松平信康, まつだいら のぶやす) was a samurai of the Muromachi period (1336–1573) and the eldest son of Tokugawa Ieyasu. Born on 13 April 1559 at Okazaki Castle, he was the heir to the Matsudaira clan, the family that would later take the Tokugawa name. His mother was Tsukiyama-dono, and his wife was Toku-hime, a daughter of Oda Nobunaga.

Nobuyasu held the position of daimyo, ruling as lord of Okazaki Castle from 1570. He is often referred to retroactively as Tokugawa Nobuyasu (徳川信康) because his father, Ieyasu, changed the family name to Tokugawa in later years. In his own lifetime, however, he was known by the Matsudaira name.

Life and Career

Nobuyasu’s common name, or tsūshō (通称), was Jirōzaburō (次郎三郎). He was also called "Okazaki Saburō" (岡崎三郎), a title derived from his position as lord of Okazaki Castle. The year 1570 marked his assumption of that castle, placing him in charge of a key stronghold in Mikawa Province.

His military career included participation in the Battle of Nagashino in 1575, a major conflict in which his father Ieyasu and Oda Nobunaga defeated the Takeda clan. Nobuyasu fought alongside the allied forces in that engagement, which is remembered as a turning point in the wars of the period.

The later years of Nobuyasu’s life were marked by political turmoil within his own family. His mother, Tsukiyama-dono, was accused of conspiring against Oda Nobunaga, Ieyasu’s powerful ally. Nobuyasu himself came under suspicion, and the relationship between father and son deteriorated. In 1579, Ieyasu ordered Nobuyasu to commit seppuku, a form of ritual suicide. Nobuyasu died on 5 October 1579 at Futamata Castle, at the age of twenty.

Why They Matter

Nobuyasu matters primarily because of what his death meant for the Tokugawa succession. As the eldest son and designated heir, his removal from the line of succession changed the course of the clan’s history. After his death, Ieyasu’s third son, Tokugawa Hidetada, eventually became the heir and later the second Tokugawa shogun.

The circumstances of Nobuyasu’s death also illustrate the brutal logic of alliance politics in the late Muromachi period. The accusation against his mother and the suspicion cast on him were tied to the delicate balance of power between the Matsudaira and Oda houses. Ieyasu’s decision to sacrifice his own son was widely seen as a move to preserve the alliance with Oda Nobunaga, whose support was essential for Ieyasu’s survival and expansion.

Nobuyasu’s story is thus a case study in how personal loyalty and family bonds could be subordinated to political necessity. His life was short, but his death had lasting consequences for the Tokugawa line that would unify Japan in the following decades.

The Name in Japanese

The name is written 松平信康.

• Kana reading: まつだいら のぶやす
• Romaji: Matsudaira Nobuyasu

The family name 松平 (Matsudaira) breaks down as:

• 松 (まつ, matsu) — "pine tree"
• 平 (たいら, taira) — "flat" or "peace"

The given name 信康 (Nobuyasu) breaks down as:

• 信 (のぶ, nobu) — "trust" or "faith"
• 康 (やす, yasu) — "peace" or "ease"

So the full name carries a meaning along the lines of "pine-tree peace, trusting peace." The character 平 in the family name is also the same character used in the name of the Taira clan, reflecting the Matsudaira clan’s claimed descent from that lineage. The given name 信康 was a common style for samurai heirs, combining virtues of loyalty and calm.

Note that the family name is often written as 徳川 (Tokugawa) in later references to Nobuyasu, because his father Ieyasu adopted that surname after establishing the Tokugawa shogunate. In his own lifetime, however, the name was Matsudaira, and that is the name used in contemporary records of his life and death.

Legacy

Nobuyasu’s legacy is largely defined by what did not happen: he never became shogun, and his line did not continue. His children, including a daughter named Myōkōin and another daughter also named Toku-hime, did not carry forward a major political inheritance. The Matsudaira clan name itself survived, but the main Tokugawa line descended from Ieyasu’s later sons.

The story of Nobuyasu has been retold in Japanese historical fiction and drama, often as a tragedy of a loyal son caught between a demanding father and a dangerous political environment. His death at Futamata Castle remains one of the most discussed episodes of Ieyasu’s early career, precisely because it shows the cost of the alliances that eventually made the Tokugawa shogunate possible.

For students of Japanese history, Nobuyasu serves as a reminder that the unification of Japan under the Tokugawa was not a clean or bloodless process. It involved personal sacrifices within the ruling families themselves, and the fate of a young daimyo like Nobuyasu was part of that larger, often harsh, political calculus.