Lifespan: Tenbun 7 (1538) to Tenshō 8 (1580)
Other Names: Genjirō (common)
Title: Governor of Owari
Lord: Uesugi Kenshin → Uesugi Kagekatsu
Father: Shibata Tsunasada
Siblings: Nagaatsu, Shigeie, sister (formal wife of Irobe Nagazane)
Shibata Nagaatsu served as a bushō during the Sengoku and Azuchi-Momoyama periods.
Nagaatsu was born as the lineal heir of Shibata Tsunasada.
Nagaatsu served as the head of the Shibata clan, kokujin, or provincial landowners, and members of the Agakita Group in Echigo Province. Nagaatsu was the lord of Shibata Castle in the Kanbara District of Echigo. The Shibata were an illegitimate branch of the Kaji clan who were the main branch of the Sasaki party founded by Sasaki Moritsuna, a bushō from the late Heian period. The Sasaki party also included the Shibata, the Takenomata, and the Ijimino clans.
Nagaatsu served Nagao Harukage and Nagao Kagetora (later known as Uesugi Kenshin). He was counted among the Generals of the Seven Units under Uesugi Kenshin (in addition to Kakizaki Kageie, Honjō Shigenaga, Kaji Harutsuna, Takenomata Kiyotsuna, Irobe Katsunaga, and Nakajō Fujisuke).
Nagaatsu excelled in diplomacy. During a rebellion by the Jōjō clan, he endeavored to lead the kokujin in Echigo, persuading some who were aligned with the Jōjō to serve Harukage instead. In 1578, the demise of Uesugi Kenshin triggered a succession struggle between Kenshin’s adopted sons, Uesugi Kagekatsu and Uesugi Kagetora, known as the Otate Conflict. Nagaatsu supported Kagekatsu who eventually prevailed and succeeded his adoptive father as the head of the Yamanouchi-Uesugi family (the main branch of the Uesugi clan).
In the course of his diplomacy, Nagaatsu, together with Takenomata Yoshitsuna and Saitō Tomonobu, arranged a peace deal with Takeda Katsuyori and he actively served with his younger brother, Ijimino Harunaga (later known as Shibata Shigeie). After the war, the Uesugi family was beset by internal conflicts and, without adequate rewards for his contributions, he died of illness in poor circumstances.
After his demise, Nagaatsu’s younger brother, Harunaga, reverted to the Shibata surname, changed his first name to Shigeie, and inherited the Shibata family.