He and his father built Takebeyama-jo Castle (Maizuru City); they made Tango Province their foodhold, and in Oei War, they defeated Hiroshige OUCHI and firmly established their position as the nucleus of bakufu.
父とともに建部山城(舞鶴市)を築城し、丹後国を地盤とすると、応永の乱では、大内弘茂を打ち滅ぼし、幕府中枢の地位をも確固たるものとした。