At this time the supply of horses from Ryoseikoku and Mimaki tended to stagnate, and also a chief executive, FUJIWARA no Nakamaro, who had a tight grip on military power in the Dajokan, caused a war (FUJIWARA no Nakamaro's War), so it was a time when the necessity to keep armaments under the direct control of those defending the emperor had been refuted.
この時期には令制国やそこに設置された牧（御厩）からのウマの貢馬が滞りがちとなり、更に太政官において軍権を握った最高責任者の藤原仲麻呂が乱を起こす（藤原仲麻呂の乱）など、天皇を守るための直轄の軍備の必要性が唱えられた時期であった。