From the time of Tamuramaro's youth, there had been a raging war with the Ezo people in Mutsu Province and in 789, the government army led by KI no Kosami was heavily defeated by the Ezo army led by Aterui.
田村麻呂が若年の頃から陸奥国では蝦夷との戦争が激化しており、延暦8年（789年）には紀古佐美の率いる官軍がアテルイの率いる蝦夷軍に大敗した。