Yoshitane was the son of Sôma Moritane (1529-1601) and ruled from Otaka in Mutsu province. He clashed frequently with the Date family but was soundly defeated by Date Masamune in 1589. The following year he submitted to Toyotomi Hideyoshi and was established at Nakamura in Mutsu. In 1600 he did not immediately respond to Tokugawa Ieyasu's call to arms in the Sekigahara Campaign and was deprived of his domain as a result. However, on the occasion of Tokugawa Iemitsu's birth in 1604, Yoshitane's family was reestablished at Nakamura.
- Initial text from Sengoku Biographical Dictionary (Samurai-Archives.com) FWSeal & CEWest, 2005