There is a brief comment about this expedition in the "Ruiju Kokushi (Book of History)" that 'Vice Commander SAKANOUE Osukune no Tamuramaro conquered the Ezo army,' which leads us to believe that Tamuramaro was playing a leading part in the expedition as one of the four Vice Commanders.
この戦役については『類聚国史』に「征東副将軍坂上大宿禰田村麿已下蝦夷を征す」とだけあり、田村麻呂は四人の副使（副将軍）の一人ながら中心的な役割を果たしたらしい。