Yoshiatsu was the son of Uesugi Takamasa and was adopted by Miura Tokitaka. He overthrew Tokitaka in 1496 and established his own son Yoshimoto at Arai while he resided in Okazaki. He became involved in a war with Hôjô Sôun when the latter took Odawara Castle. Yoshiatsu was attacked at Okazaki in 1512 and fled to Arai. The Hôjô defeated Yoshiatsu's allies, the Ota, and Yoshiatsu was left isolated. After a long siege Arai fell to the Hôjô in 1516. Yoshiatsu committed suicide along with Yoshimoto.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005