In 1221, when the Jokyu War broke out, Yoshitane who joined the War with his son, Tanetsuna (it is said that his grandson, Tanetsugu SOMA, also joined), as the army of bakufu (Japanese feudal government headed by a shogun) played an active role in the Battle of Uji-gawa River and the Battle of Seta (no Karahashi) Bridge in Omi Province and rendered distinguished military service.
1221年、承久の乱が起こると子の胤綱と共に（孫の相馬胤継もいたとも）幕府軍として参陣して、宇治川の戦いや近江国瀬田橋の戦いで活躍して、軍功を挙げた。