They expanded their power from Kazusa Province into Hitachi Province and Shimousa Province, forming armed groups in the Bando (old Kanto) region, which became the foundation of the Taira clan as samurai.
上総国ばかりでなく常陸国や下総国にも勢力を拡大、坂東に武士団を形成し武家平氏の基盤を固めた。