In 1583 he attacked Mitsumasa ISHIKAWA, the castellan of the Domeki-jo Castle in Tamura territory (he banished Hisayoshi in conspiracy with the old retainer of the Ishibashi clan and Yoshitsuna), defeated Kiyoaki TAMURA with the support of Moritaka ASHINA, who was an enemy of the Tamura clan, and succeeded in gaining independence.
こうして1583年、田村領の百目木城主石川光昌（石橋氏旧臣、義綱と組んで尚義を追放した）を攻撃、田村氏と対立していた蘆名盛隆の支援を受けて田村清顕を破り独立を果たす。