Moritsuna and his old brothers defeated the Taira clan in the Battle of Fujigawa on October 20, 1180, and were granted a former territory of Sasakinosho in the grant of honors held on August 23, 1180 at the provincial capital of Sagami Province for the first time after the raising of army.
10月20日の富士川の戦いで平氏を破り、23日に相模国国府で行われた挙兵後初の論功行賞では、旧領の佐々木庄を安堵された。